They Lost Huge Parts of Their Brains, But Their Knowledge and Recollection Were Preserved

 When people think of neuroscience experiments, they typically think of experiments done with mice. If they think of neuroscience experiments involving humans, they may think of some experiment involving the use of some drug, with a test to see whether the drug affects mental performance.  Such experiments are formally designed with things such as a set of test subjects, a set of control subjects that do not have any intervention occurring to them, and so forth. 

But some of the most important experiments in neuroscience have been those that were not part of some procedure declared as an experiment. The experiments have occurred when some large part of a human brain was removed in surgery. Whenever such an operation is done, it is an important experiment that tests the credibility of the claims that neuroscientists so often make. 

Neuroscientists are always claiming that learning occurs through some brain action, that memories are stored in brains, and that recall of a memory occurs by some action of the brain. Neuroscientists senselessly keep making such claims despite their lack of any credible theory describing how any such things could be done by a brain. When a neuroscientist is asked to explain how a brain could store some newly learned knowledge, a scientist will typically engage in some vague, vacuous hand-waving which typically consists of merely reciting some little slogan or sound bite such as "synapse strengthening." There is nothing to speak of behind such a phrase, which is a mere vacuous catchphrase. When asked to explain how a human can instantly recall some knowledge, a neuroscientist will typically say nothing but the most vacuous phrase such as "stored information is recalled." 

Although not called "experiments," every time a large part of the brain is removed from a human, a very important experiment is being performed, one that sheds light on whether neuroscientist claims about memory are credible.  Under the theory that memories are stored in brains and retrieved by brains, we should expect to observe certain things:

(1) We should expect that there should be some deterioration in the ability of humans to learn new information. Such a deterioration might be small or large, depending on where brain tissue was extracted, and how brain tissue was extracted. 

(2) We should expect that there should be some loss of learned knowledge and episodic memories. Such a deterioration might be small or large, depending on where brain tissue was extracted, and how much brain tissue was extracted. 

Item (2) is often overlooked, but is obviously something to be expected under the theory that brains store memories. Imagine if someone writes down what happened to him each day, in a large book that originally consisted of blank pages. Obviously if you were rip out a large chunk of these pages and burn them, that would cause a large loss of the information that had been recorded.  It is just as obvious that if memories are stored in brains, then surgically removing some large chunk of the brain should cause some large loss of what a person had learned or the memories the person had. 

If memories are stored in the brain we should expect that a surgical removal of a large amount of brain tissue might produce effects such as these:

(1) A loss of the ability to understand some words in a person's language. Each recognition of a word that occurs when a person hears something involves the use of some learned knowledge that a person acquired sometime in his life.  

(2)  A loss of the ability to speak or write some words in a person's language. Each use of a word that occurs when a person speaks something or writes something involves the use of some learned knowledge that a person acquired sometime in his life.  

(3) A loss of the ability to recognize various types of images such as particular faces or particular words or particular symbols. Every time a person recognizes a word or a face or an object or a symbol, that involves the use of some  learned knowledge that a person acquired sometime in his life.  

(4) A loss of the ability to recall various concepts and facts that the person had learned at some time in his life. For example, a person might no longer remember what country or city he lived in, or what his name was, or what his address was. Or a person might no longer be able to explain who some famous historical figure was, someone such as Jesus or Napoleon. 

(5) A loss of episodic memories. For example, a person might no longer be able to tell you the story of his life, or tell you what type of activities he engaged in last year. 

To test whether memories are stored in brains, we can track down case histories of people who had large amounts of brain tissue surgically removed, and examine which, if any, of the effects above occurred.  Let's look at some examples of such cases. 

First, let's look at the case of Beth Usher of Storrs, Connecticut (part of the USA). Beth was mentioned in an article in the LA Times, which says she was one a group of epileptic children who had half of their brain removed, to stop very bad seizures that drugs could not stop. The article stated this:

 "How is it that 8-year-old Beth Usher of Storrs, Conn., can lose her left hemisphere, yet retain her large repertoire of knock-knock jokes? Beth’s memories survived not just the loss of brain tissue, but also the 32 days that she spent in a coma, the result of some brain stem swelling that occurred in response to the trauma of surgery. Shortly after Beth regained consciousness, her father began quizzing her about people and places from her past. Brian Usher didn’t get very far. 'Dad,' Beth interrupted, with a trace of impatience. 'I remember everything.'" 

We have here the explicit claim that Beth's memories survived the removal of the left half of her brain.  The article mentions specific things that Beth could still remember, and makes no mention of any memory or knowledge that was lost after half of her brain was removed. 

Another case is discussed here, in a book chapter of a textbook. We read of a patient E.C. who had a large brain tumor. To treat the tumor, the left half of the patient's brain was removed, in a hemispherectomy operation. We read that "the entire hemisphere was removed in one piece" on December 7, 1965. We read that "immediately following hemispherectomy" the patient had an "ability to follow simple verbal commands."  We read on page 107 that "the patient spontaneously articulated words and short phrases fairly well immediately after the operation."  

The discussion of the patient's retention of previous knowledge is rather frustrating in its lack of a comprehensive treatment. We read that this patient E.C. "gave the correct number of years when asked how long he had lived at his house." We read on page 107 that on January 26, 1966 (about six weeks after the operation) he "slowly but correctly selected four of the first six items from six pages, each with four items to choose from, before indicating he was tired" when given the Peabody picture vocabulary test. Such a test involves a tester speaking a word, and the user pointing to the correct picture in a grid of 4 pictures. 

The image below (from the paper here) shows an example of one of the pages. The word spoken by the tester is "citrus."

The result described above (4 out of 6 correct on six such pages) clearly suggests that patient E.C. retained his learned knowledge after the left half of the brain was removed. Since the test was given only six weeks after the operation, and E.C. was in a recovering state during those weeks in which he was not being schooled, we cannot explain such a result as being due to knowledge acquired during those six weeks. We also read on page 107 that on June 3, 1966 patient E.C. correctly named 85 out of 112 items on such a test. No mention is made of schooling occurring during the first six months of 1966. 

According to the paper here, "In the fifth postoperative month, E.C. showed sudden recall of whole old familiar songs (e.g., My

Country 'Tis of Thee, Home on the Range, church hymns)."

On page 109 we read of three other cases of the removal of the left half of the brain, and we read that "speech and verbal comprehension were present immediately after left hemispherectomy in all three cases." We read nothing about any loss of knowledge or episodic memories in any of these cases. 

In the scientific paper here, we have on page 248 and page 250 before and after test scores for various subjects who had of their brains removed in hemispherectomy operations.  The IQ score differences are slight. IQ tests don't involve learned information, but almost any IQ test would be largely a test of memory, as it would be a largely a test of ability to read test questions.  

On the same pages we have before and after test scores for Peabody Picture Vocabulary Tests given to various subjects who had  half of their brains removed in hemispherectomy operations.   In these tests, someone is shown picture cards like the one below. The tester speaks a word corresponding to one of the pictures, and the subject tested is asked to point to the correct picture matching that word.  These tests are tests of memory retention after removal of half of the brain.  On these memory tests there was no decline in the score of 21 subjects mentioned on page 248, and no decline in 7 subjects mentioned on page 250. 

The 2021 paper "Preserved Cognition After Right Hemispherectomy"  by Mark Bowren, Jr,  Daniel Tranel and Aaron D. Boes tells us the fairly recent case of a woman who had almost the entire right half of her brain removed, but is apparently suffering very little cognitive damage from this removal. We read that the woman had a brain stroke at age 29, and that doctors treated her brain problem by removing almost all of the right half of her brain, in an operation called a hemispherectomy. We read that "In the days after surgery, she was described as alert, cooperative, and having normal language and interactions with her providers." We read no mention in the paper of a loss of acquired memories.  

The phrase "having normal language" is a very important indication that learned knowledge was preserved after almost all of the right half of the brain was removed.  Every time a person uses language in speech, that involves a use of acquired memories. Every single use of a particular word requires a memory of the definition of that word.  

Also we read that two months after the stroke, this patient CB had "intact expressive language and reading comprehension."  The paper does not tell us how many weeks after the stroke there occurred the removal of almost all the right half of the brain. But from the timeline given we know that this sentence refers to some time less than two months after the operation occurred.  Because you cannot learn a large fraction of a language in less than two months, we can presume that the patient had "intact expressive language and reading comprehension" directly after having had almost all of the right half of her brain removed, particularly given that we are told that the patient had "normal language" days after the operation. 

In a scientific paper ("Why Would You Remove Half a Brain? The Outcome of 58 Children After Hemispherectomy −−The Johns Hopkins Experience: 1968 to 1996") we read about how surgeons at Johns Hopkins Medical School performed fifty-eight hemispherectomy operations on children over a thirty-year period. Eleven of these children had the left hemisphere of their brains removed; most of the rest had the right hemisphere of their brains removed.  The paper states this:

"Despite removal of one hemisphere  [i.e. one half of the brain], the intellect of all but one of the children seems either unchanged or improved....Although there have been major concerns about loss of language after left hemispherectomy, all eleven of these children have regained virtually normal language....It is tempting to speculate, that the continuous electrical activity of these severely dysfunctional hemispheres interferes with the function of the other, more normal hemisphere. This might explain why motor function improves after hemispherectomy and why language recovers after removal of the dysfunctional left hemisphere, but does not seem to fully transfer before surgery. Perhaps it also partially explains intellectual improvement in these children after removal of half of the cortex. We are awed by the apparent retention of memory after removal of half of the brain, either half, and by the retention of the child’s personality and sense of humor."

There is a reason why we can be confident that removal of half of a brain in hemispherectomy operations does not cause any major loss of learned memories.  If there was a case of any such thing happening, you can believe that it would be endlessly recited by those who wish for us to believe that memories are stored in brains. But there is no such case that is cited. 

The visual below "speaks volumes" on this topic. It is the result of a search on Google Scholar for "amnesia after hemispherectomy." "Hemispherectomy" is the standard name for the operation that has been performed thousands of times, in which half of the brain is removed to stop very bad seizures. "Amnesia" is the main term used for a loss of episodic memories.  Any search on Google Scholar will produce very many results when there are cases corresponding to such a search. For example, doing a Google Scholar search for "vision loss after automobile accident" produces many results. But doing a search for "amnesia after hemispherectomy" produces zero results.

Entitled "Man With Half a Brain," the 1912 newspaper article below (which you can read here) tells us of a soldier who was shot in the head. First, we are told that he lost his memory, but then the article says that "gradually his memory has returned, and he recollected what happened in his childhood." Then the article tells us this: "And now he remembers everything up until the third day before he was shot." 

The news story here documents a very clear case of the preservation of memory after the removal of the left half of the cerebrum. We read of a 47-year-old man who had the left half of his cerebrum removed. We read this:

"Dr. Smith said the patient's memory of events before the operation 'was well preserved, much better than anyone expected.' Tests following surgery show Coe can perform many functions traditionally thought impossible after removal of the brain's dominant hemisphere. Immediately following surgery, Coe still had the ability to speak spontaneously."

A report like this does not merely contradict the claim that the brain is the source of the mind. It also contradicts the claim that the brain is a storage place of memories. 

The results discussed in this post deserve to be pondered at great length. The results indicate very strongly that the human brain is not any storage place of human memories. After considering such results, you should also ponder the most important null result of neuroscience research: the fact that brain tissue from thousands of living and recently deceased humans has been microscopically studied at great length, with the most powerful microscopes; but no one has ever found the slightest trace of learned information or any episodic memory by such microscopic examination. No one found a single phrase, a single word or even a single letter of the alphabet after microscopically examining brain tissue. Nor did anyone ever find by microscopic examination of brain tissue any trace of anything a human ever saw or heard. 

Surprising Studies on Memory Loss or IQ Changes After Brain Surgery or Brain Damage

Neuroscientists typically claim that memories are stored in the brain. There are some very complex ways and very simple ways in which such a hypothesis can be tested. A very complex way would be to use dissection to see whether any sign of human memories can be found. You could do this in two different ways: (1) by dissecting the brains of people who had recently died, looking for learned information such as facts learned in school; (2) by analyzing tissue removed from the brains of living people, to look for  learned information such as facts learned in school. There are plenty of opportunities for the second of these methods, because brain tissue is often removed to treat diseases such as epilepsy. Sometimes an entire half of the brain is removed in an operation called a hemispherectomy, to treat very severe and frequent seizures. Epilepsy is also treated by less severe operations that involve removing much less than half of the brain. 

Examining removed brain tissue has never produced any support for the claim that memories are stored in brains. No one has ever seen any words or letters by looking at brain tissue through a microscope. No one has ever used a microscope to look at brain tissue of some particular person, and seen images corresponding to sights that person  previously saw. No one has ever seen any sign of encoded information by looking at brain tissue through a microscope,  other than genetic information which is not information that anyone learns through school or experience.  

The method described above is a very complex method that might require the use of very sophisticated equipment such as electron microscopes. But there is a very simple way of testing the hypothesis that memories are stored in brains. You can simply do what may be called a  "loss of learned information" test, testing someone both before and after the person had surgery to remove some of their brain tissue. You can look for loss of memories and learned information that had been acquired before the operation. 

Such a test would be different from a typical memory test. A typical memory test might measure how well someone can remember some new information he was asked to memorize. But a "loss of learned information" test would only test whether something learned or remembered before some brain surgery had been lost by the act of surgery itself. 

You would think that scientists eager to prove their claims that memories are stored in brains would often do such a "loss of learned information" test.  But it seems very hard to find examples of such tests in the scientific literature. 

Let us look at some papers that may be relevant to discussions of whether human brains store memories.  We must carefully distinguish between two types of tests:

(1) A "performance on new learning" memory test will test how well some person can still acquire different types of new memories after having lost some brain tissue.

(2) A "loss of old memory" test will test whether a person lost some memory he had acquired, because of some loss of brain tissue.  

The second type of test is more relevant to whether the brain stores memories.  Removal of some brain tissue might damage your senses or perception in a way that might decrease your ability to learn new things and acquire new memories. But that would not show that your previous memories acquired before such a removal were stored in your brain. Similarly, if you make a person blind, that will reduce his ability to learn, but that does nothing to show that brains store memories. 

We must also carefully distinguish between a random pool of brain tissue loss subjects, and a pool of subjects who have been selected because they showed symptoms of memory loss. I have looked at quite a few papers in which we are told that some pool of subjects was selected for both brain tissue loss and also memory problems. Tests of the extent of memory loss in such persons may be giving a very misleading impression, because only subjects having memory loss were selected for the tests. Such studies may merely show that "people with memory problems have memory problems." 

It seems that our medical professionals are usually bad about testing preservation of memories after doing operations that remove half of a brain or a large fraction of the brain. I think this may be because they do not want to do a test that will produce results that contradict their dogma that memories are stored in brains. But here and there in the scientific literature you will be able to find some tests that serve as tests of how well memories were preserved after half of the brain was removed. In some other cases, we will be able to infer that there was  little or no loss of memories acquired before the operation, either because of a lack of mention of any such thing (which would be noteworthy and worthy of mention if it occurred), or because of some general assurance that the operation usually produced "no serious complications," a claim that should only be made if previously acquired memories were well-preserved.  

Let us look at some of the papers that might be relevant. 

• The paper here ("Unexpected amnesia: are there lessons to be learned from cases of amnesia following unilateral temporal lobe surgery?") tells us that "Cases of amnesia following unilateral temporal lobe surgery are rare." It tells us that "Davies and Weeks (1993) did report one case of postoperative amnesia in a series of 58 cases of unilateral temporal lobectomy, whereas Walczak et al. (1990) found one case of marked deterioration in memory from a preoperative normal state in their series of 100 patients who underwent such surgery." The authors state, "We were able to locate nine definite cases of amnesia following unilateral temporal lobe surgery in the English language literature." But the paper gives us no interesting accounts describing amnesia in any of these cases. We do have a Table 3 that has "before" and "after" columns for seven of the nine cases. The table fails to mention much of anything backing up claims that the patients had amnesia in the sense of loss of memories or learning they had acquired before the surgery. We have "before and after" IQ scores for the first five subjects, which show no significant difference (there sometimes being an increase).  For patient 6 there is no data, and for patient 7 we read "postoperative scores on executive and language function similar to preoperative scores." In the column labeled "Post-surgery memory functioning" we hear of some declines in memory performance tests for some of the subjects, but we hear nothing about a loss of memories that they had acquired before the operation.  And some of the results in that column involve tests taken years after the surgery, so we don't know whether any declines reported were the result of the surgery. In short, the paper fails to provide any good evidence that memories or learned information can be lost by temporal lobe surgery for epilepsy. 
• The paper "Memory outcome after temporal lobe epilepsy surgery: corticoamygdalohippocampectomy versus selective amygdalohippocampectomy" fails to discuss any measurements or observations about how acquired memories or learned knowledge declined after brain surgery that removed substantial tissue. It does tell us that for 63 patients IQ went up by about five points after such surgery, and that for another 60 patients IQ increased by nearly five points. The paper tells us that "General intelligence increases after epilepsy surgery." 
• Almost the same claim is made by the paper here ("Psychiatric and Neuropsychological Problems in Epilepsy Surgery: Analysis of 100 Cases That Underwent Surgery"), which tells us, "The full IQ score of the Wechsler Adult Intelligence Scale–Revised (WAIS-R) was increased after temporal lobectomy in 75% of the cases (p < 0.01; n 4 44)." 
• The paper "Retrograde amnesia in patients with diencephalic temporal lobe or frontal lesions" has some interesting graphs showing memory tests in a group of subjects that included "15 patients with dicephalic lesions, 15 patients with temporal lobe lesions, 15 with frontal lobe lesions and 20 healthy control subjects." We have graphs showing performance on tests that include tests of autobiographical incidents, news recall and famous faces. All of the patients with lesions are able to produce scores ranging from about 70% to 30% of the scores produced by control subjects.  This is not a very impressive result, considering that the paper says, "The patients were selected in all cases on the basis of their having significant anterograde memory impairment in association with clinical and CT scan evidence of pre- dominantly focal lesions in either the temporal or frontal lobes or the diencephalon."  Since both having brains lesions and being not good at remembering the past was a requirement for being chosen in the study, the paper fails to show a link between the lesions and the memory performance. Similarly, if you did a study that only accepted subjects who were both gay and alcoholic, that would do nothing to show that being alcoholic tends to make people gay. 
• The paper "Retrograde amnesia in patients with hippocampal, medial temporal, temporal lobe, or frontal pathology" suffers from the same shortcoming.  We have some graphs showing inferior memory performance on five patients, on tasks of autobiographical recall, recalling famous news events, and recalling famous faces. But the paper eventually tells us that these patients "were selected on the basis of significant anterograde memory loss and MRI evidence that regional brain atrophy was restricted to the medial temporal lobe structures."  So the result merely tells us that people who have trouble remembering what they learned have trouble remembering what they learned. A random sample of five subjects with the same brain tissue loss might tell a very different tale. 
• The paper "Clinical outcomes of hemispherectomy for epilepsy in childhood and adolescence" (about surgeries removing half of a brain) tells us that "the overall developmental/cognitive category was unchanged following surgery in 23 out of 27 children," and that "two children showed a >15 point improvement in DQ/IQ following surgery,"  referring to a substantial increase in intelligence as measured by IQ tests. 
• The paper here "Seizure control and developmental trajectories after hemispherotomy for refractory epilepsy in childhood and adolescence" (in Figure 4) describes IQ outcomes for 41 children who had half of their brains removed in hemispherectomy operations in Freiburg, Germany. For the vast majority of children, the IQ was about the same after the operation. The number of children who had increased IQs after the operation was greater than the number who had decreased IQs. 
• The paper "With childhood hemispherectomy, one hemisphere can support—but is suboptimal for—word and face recognition" involved tests on 15 left hemispherectomy patients, 24 right hemispherectomy patients, and 58 age-matched control subjects. A hemispherectomy typically involves removal of one-half of the brain to stop very frequent epileptic seizures. According to Figure 5, most of the patients who had a hemispherectomy were only "mildly impaired" in their ability to recognize words and faces, with a few being "moderately impaired," a few others having "average" performance, and one having "above average" performance.  The tests performed seemed to have been purely "performance on new learning" tests. We read that "Childhood hemispherectomy patients showed above 80% accuracy on tasks of face and word recognition," and the paper calls this "surprisingly good performance."
• A 2015 scientific paper ("Brain abscess: surgical experiences of 162 cases") looked at 162 cases of surgery to treat brain abscess, in which parts of the brain undergo the cell death known as necrosis, often being replaced with a yellowish pus. The article contains quite a few photos of people with holes in their brains caused by the abscesses, holes in their brains of various sizes. The paper says that “complete resolution of abscess with complete recovery of preoperative neuro-deficit was seen in 80.86%” of the patients, and that only about 6% of the patients suffered a major functional deficit, even though 22% of the patients had multiple brain abscesses, and 30% of the abscesses occurred in the frontal lobe (claimed to be the center of higher thought). Interestingly, the long review article on 162 brain abscesses treated by brain surgery make no mention at all of amnesia or any memory effects, other than to tell us that “there was short-term memory loss in 5 cases.” If our memories really are stored in our brain, how come none of these 162 cases of brain abscesses seem to have shown an effect at all on permanent memories?
• Similarly, a scientific paper ("Brain abscess: clinical aspects of 100 patients") about 100 brain abscess cases (in which one fourth of the patients had multiple brain abscesses) makes no mention of any specific memory effect or thinking effect. It tells us that most of the patients had “neurological focal deficits,” but that's a vague term that doesn't tell us whether intellect or memory was affected. (A wikiepdia.org article says that such a term refers to "impairments of nerve, spinal cord, or brain function that affects a specific region of the body, e.g. weakness in the left arm, the right leg, paresis, or plegia.")   The paper tells us that after treatment “80 (83.3%) were cured, eight (8.3%) died (five of them were in coma at admission), seven had a relapse of the abscess,” without mentioning any permanent loss of memory or mental function in anyone.
• Another paper ("Epidemiology of brain abscess in Taiwan: A 14-year population-based cohort study") discusses thousands of cases of brain abscesses, without mentioning any specific thinking effects or memory effects. 
•  Another paper ("Retrospective analysis of 49 cases of brain abscess and review of the literature") refers to 49 brain abscess patients, and tells us that "the frontal lobe was the most common site," referring to the place that is claimed to be a "seat of thought" in the brain. But rather than mentioning any great intellectual damage caused by these brain holes, the paper says that 39 of the patients “recovered fully or had minimal incapacity,” and that five died.
• A paper tested the ability to recognize faces and words in a group of control subjects and about 39 subjects who had undergone hemispherectomy, typically to remove half of their brains. Most of those who had the hemispherectomy operation performed almost as well as the normal controls.  We read, "This performance level is perhaps surprisingly high, relative to the brain volume resected  [removed] (often close to 50%), hinting at a nonlinear degradation of function with resection. Second, the patients' accuracy was not dependent on the hemisphere removed. That is, the single LH or RH of patients showed comparable performance on face and word recognition."
• The paper "Memory outcomes following hemispherectomy in children" fails to mention in its abstract any loss of episodic or conceptual memories after hemispherectomy operations typically involving removal of half a brain. It says, "Undergoing hemispherectomy was not necessarily associated with declined memory performance, with the majority of patients showing stable scores."
• The paper "The Cognitive Outcome of Hemispherectomy in 71 Children" describes outcomes of operations typically removing half of a brain to stop very frequent seizures. The paper gives us in Table 7 the pre-operation and post-operation IQ scores for 31 different children. The decline in IQ is only small. The children went from an average IQ of  80.5 to an average IQ of 75.7. 26 of these children were given a test called the Peabody Picture Vocabulary Test. For these 26 children the average score increased from 79.0 to 82.1. This test is very important because it is effectively a test of previously acquired knowledge. In the test a person is shown a series of four pictures, and is asked a question such as "Which picture shows laughing?" The test therefore measures previously acquired knowledge. The increase in the score on this test is most remarkable. It is not at all what we would expect if the human brain stores memories. Under the hypothesis that the brain stores memories, removal of half of a brain should cause a sharp decline in performance on this test. Similar results are shown in Table 9. We have pre-operation and post-operation IQ scores for 15 different children (not the ones described in Table 7). The decline in measured IQ is less than a single point. Scores on the Peabody Picture Vocabulary Test rose from an average of 43.0 to an average of 51.7. Another paper summarizes these results by saying, " Pulsifer et al. ... reported cognitive outcomes in 71 children who underwent hemispherectomies and found little changes in cognitive performance pre- and post-surgery."
• The paper "Long-term functional outcomes and their predictors after hemispherectomy in 115 children" did not test for IQ or memory, but reports on things such as speech ability, walking ability and reading ability. We read this: "In this cohort of 115 children, at a mean follow-up of 6.05 years after hemispherectomy, 83% patients walked independently, 73% had minimal or no behavioral problems, 69.5% had satisfactory spoken language skills, and 42% had good reading skills."
• The paper "Hemispherectomy in adults patients with severe unilateral epilepsy and hemiplegia" discusses "25 adults who presented severe unilateral epilepsy and hemiplegia and underwent anatomic or functional hemispherectomy in between 2006 and 2011."  16 of these were "anatomic hemispherectomies" apparently involving removal of half of the brain, and the other nine were "functional hemispherectomies."  Very remarkably, we are told "All of the patients’ postoperative scores of overall QOL, full IQ, verbal IQ and performance IQ improved compared with pretreatment scores."  We don't read anything about before-and-after tests of memory retention, but we read that "Hemispherectomy is a safe operation for epileptic adults with hemiplegia and serious seizures and seldom leads to severe complications."  We may presume that the people having these operations still preserve almost all their memories, seeing that the loss of much of your memories would certainly be a "severe complication." 
• The paper here ("Retrograde amnesia after traumatic injury of the fronto-temporal cortex") tells us of a man who suffered severe brain damage after falling from a horse. He was in a coma for 6 weeks, and his MRI showed very extensive brain damage in multiple areas. The man was given various tests of how good his acquired memories were preserved. He scored 33 out of 60 on the Famous Faces Test, and 70 out of 100 on the Semantic Knowledge Test.  He was able to remember 8 of 16 objects from his past. He scored 100 on an IQ test. Since the test was done four years after the fall, we don't know how much of this decline was caused by the fall. 
• The paper "The Effect of Early and Late Brain Injury upon Test Scores, and the Nature of Normal Adult Intelligence" is behind a paywall. But from the freely available first page we get the interesting information that after searching for IQ scores recorded about brain surgery, the author found 15 subjects, and found that they had an average post-operative IQ of 108.   The author also found another group of 23 brain surgery patients who had an average post-operative IQ of 107. We are told "in none was there postoperative loss" of IQ.
• The paper "When only the right hemisphere is left: Studies in language and communication" reports on the case of a patient BL of "above normal intelligence" who underwent a left hemispherectomy at age five. Despite lacking the left half of his brain, BL "attended regular elementary and high school and graduated from college with a Bachelor's degree with a double major in business and sociology," he "played the baritone horn in a band," and worked "several years as an accountant in international business." The paper reports BL scoring normally on most of the cognitive tests he took.
• The paper "Functional consequences of hemispherectomy" gives us in Table 1 before-and-after IQ scores for 12 children who had half of their brains surgically removed. The worst result was a decline in IQ of 11 points, occurring for only one of the subjects. The best result was an increase in IQ of 8 points, which occurred for three different subjects. Overall, there was more of an increase in IQs than a decrease.  
• The paper "Long-term outcome of hemispheric surgery at different ages in 61 epilepsy patients" examines the IQ effects of removing half of a brain.  Near the bottom of Table 2 we are told that out of 55 patients, only 5 experienced post-surgical "intellectual deterioration," with 50 categorized as "not worse" in regard to "intellectual deterioration." 21 of these 55 patients are called "better" in regard to "intellectual improvement," and 34 are called "not better."  We read, "More than 80% appeared improved or unchanged in intelligence following surgery." We don't hear much specifics on memory, but we get the claim that these "remove half the brain" operations have "low risk of adverse cognitive effects." 
• In 1994 Simon Lewis was in his car when it was struck by a van driving at 75 miles per hour. The crash killed Lewis' wife, and “destroyed a third of his right hemisphere” according to this press account. Lewis remained in coma for 31 days, and then awoke. Now, many years later, according to the press account, “he actually has an IQ as high as the one he had before the crash.” In 1997, according to the press account, Lewis had an IQ of 151, which is 50% higher than the average IQ of 100. How could someone be so smart with such heavy brain damage, if our brains are really the source of our minds?  
• In a scientific paper "Why Would You Remove Half a Brain? The Outcome of 58 Children After Hemispherectomy −−The Johns Hopkins Experience: 1968 to 1996" by Vining and others, we read about how surgeons at Johns Hopkins Medical School performed fifty-eight hemispherectomy operations on children over a thirty-year period. Eleven of these children had the left hemisphere of their brains removed; most of the rest had the right hemisphere of their brains removed.  The paper states this: "Despite removal of one hemisphere  [i.e. one half of the brain], the intellect of all but one of the children seems either unchanged or improved. " We are told "language recovers after removal of the dysfunctional left hemisphere," and the authors speculate about why it is they saw "intellectual improvement in these children after removal of half of the cortex." The authors state, "We are awed by the apparent retention of memory after removal of half of the brain, either half, and by the retention of the child’s personality and sense of humor." The final statement is very important. Although the authors do not give us the results of exact tests documenting a preservation of memory, the statement I just quoted suggests they observed a preservation of episodic and factual/conceptual memory after half of the brain was removed. 
• The paper "Cognitive Impairment 3 Months After Moderate and Severe Traumatic Brain Injury: A Prospective Follow-Up Study" gives us the result of cognitive tests on people who had brain injuries as the result of events such as falls and traffic accidents.  We have some tables that are hard to read. In the Discussion section we read that after moderate Traumatic Brain Injury (TBI), "most patients had a normal neuropsychological assessment," with no more than 1 score much below normal (or, to put it more technically, no more than 1 score below 1.5 standard deviates below the norm).  We read that "even after severe [brain] injury, normal performances were found in one third of patients." The authors say, "This was unexpected." We are told that the average total IQ score of 35 subjects with moderate traumatic brain injury was an above-average score of 109, and the average total IQ score of 26 subjects with severe traumatic brain injury was an above-average score of 103. There is a reason to suspect that some subjects may deliberately perform poorly in such tests. Some of the subjects (such as those injured in a crash) may have pending law suits, and may think that good performance in cognitive tests may reduce their chance of being rewarded lots of money in a law suit. 
• At the page here, we read an account of a girl who had the left half of the brain removed in a hemispherectomy operation, to try to stop severe seizures. We hear of a successful operation. We are told, "In addition to the seizures, Rehab also struggled with being able to remember things before her surgery." In the next sentence we hear one of the girl's parents saying, "Her memory was so poor, but now she remembers everything."  This is the opposite of what you would expect under the "brains make minds" hypothesis. 
• The paper "Neuropsychological functioning during the year following severe traumatic brain injury" studied cognitive functioning in 65 subjects who had severe brain damage, mostly after road traffic crashes. The patients were rated with a level of impairment of "mild" or "severe" on various measures, based on tests 6 months after the injury and 1 year after. Fewer than half of the subjects were rated as having "severe" impairment in memory performance tests taken at the 1-year mark. Only 9% of the subjects were rated as having "severe" impairment in one test of executive function at the 1-year mark, with a minority rated as having "severe" impairment in another test executive function at the 1-year mark. One test of attention at the 1-year mark result showed only 8% with a severe impairment, and another test of attention at the 1-year mark result showed only 28% with a severe impairment. There is a reason to suspect that some subjects may deliberately perform poorly in such tests. Some of the subjects (such as those injured in a traffic accident) may have pending law suits, and may think that good performance in cognitive tests may reduce their chance of being rewarded lots of money in a law suit. Moreover, we must also wonder whether the scientists selecting the subjects had a bias in looking for subjects with particularly bad memory problems. The average IQ of the brain-damaged subjects was 93, and we don't know whether this below-average result was caused by brain injury.  There is reason to suspect that the set of average people suffering from traffic accident brain damage may be slightly below average in IQ, given that higher IQ might tend to avoid such accidents. 
• The paper "Association of Traumatic Brain Injury With Dementia and Memory Decline in Older Adults in the United States" used a very large sample of 9,794 patients who had an assessment of traumatic brain injury.  The study says, "There was no significant relation between history of TBI [traumatic brain injury] with LOC [loss of consciousness] and memory score or memory decline." We read this: "In a nationally representative prospective cohort of older adults free of dementia at baseline, we did not find evidence for any long-term associations between history of TBI [traumatic brain injury] with LOC [loss of consciousness]  (of unknown frequency and severity) and risk of dementia over 14 years of follow-up. " We read that "similarly, decline in memory performance did not differ between participants with or without history of TBI with LOC." The authors state, "our findings showing no association between TBI history with LOC and dementia are consistent with the results of several other recent studies looking at dementia, AD [Alzheimer's Disease], or AD biomarkers or neuropathology." 
• The paper "Working Memory after Traumatic Brain
  Injury in Children" tested working memory in eighty children with mild or severe traumatic brain injury (TBI). The paper has nice easy-to-read graphs comparing the performance of the brain-injured with controls, and the first two of the graphs show no appreciable difference in performance in two working memory tests, even when comparing the severe cases with control (uninjured cases).  
• The paper "Central executive system impairment in traumatic brain injury" is one that does not give us a random sample of patients with traumatic brain injury, because the paper tells us this about its 64 patients: "Patients were selected for participating in the study if they complained of lack of attention, poor
  memory or loss of efficiency in everyday life." Despite such a selection bias, Table III of the paper tells us that the majority of the subjects had "normal performance" in long-term memory acquisition, long-term memory storage, long-term memory delayed recall, sustained attention and short-term memory, with an average of about 60% of the subjects being normal in such areas.  
• At the University of Chicago page here, we read, "Nordli recalled a patient whose IQ rose to 100, a normal intellect, from 80 before hemispherectomy." The patient seemed to get much smarter after they took out half of the brain. 
• The very interesting paper "Preserved Cognition After Right Hemispherectomy" gives us extensive performance tests for a woman who had almost all of her right brain removed after a severe stroke at age 29. We have a very good visual showing that her performance on a wide variety of cognitive tests is average or slightly below average. 

A 2020 paper gives us an indication of the appalling failure of neuroscientists and doctors to properly test for losses of pre-surgical episodic memories and pre-surgical learning in people who had hemispherectomy operations. We read this:

"Only four studies have investigated memory functioning prior to and following hemispherectomy surgery. It is worth noting that all used short-term memory tasks, typically involving immediate repetition or recognition and did not test for more challenging aspects of memory involving recall or recognition over longer delays."

The authors of a 2017 paper tell us something similar. Referring to hemispherectomy operations in which half of the brain is removed, it says this:

" Physicians have long wondered about the surprising finding that one can lead a normal life with only one hemisphere....

The discrepancy between cerebral and cognitive functioning in these cases is strikingly highlighted by the fact that most patients, even adults, do not seem to lose their long-term memory such as episodic (autobiographic) memories. Even so, this puzzle, and possible explanatory models for this retention of long-term memory, is only rarely

discussed in the medical literature dealing with hemispherectomy. Although memory features are sometimes assessed by using the Wechsler Memory Scale (e.g., Loddenkemper et al., 2004), we were unable to find a single peer-reviewed publication in which the peculiar retention of the patient's autobiographic memory was explicitly addressed. That said, this remarkable phenomenon was at least casually mentioned by authors such as Dandy (1933) and Bell and Karnosh (1949), who stated that their patient's memory seemed unimpaired after hemispherectomy. Similarly, Vining et al. (1997) were surprised by the apparent retention of memory after the removal of the left or the right hemisphere of their patients. Dorman (1991) described the extraordinary case of a subject who was able to perform brilliant calendar calculations, although his left hemisphere had been removed several years before."

Despite this appalling failure to properly test whether episodic memories and learned information are preserved after removing half of a brain, several of the studies quoted above make statements strongly suggesting that such memories are preserved after removal of half a brain, contrary to the dogma that memories are stored in brains. And when studies such as the ones above tell us that there are usually no major cognitive effects of removing half of a brain, we can regard this as being a rather clear indication that episodic memories and learned information are well-preserved after removal of half of a brain, as any major loss of such  episodic memories and learned information would be a severe cognitive effect that should be reported. 

The quote above refers to Dandy. Here is the basis of the reference. The case of Dandy's patients are reported in the American Journal of Psychology, Vol. 46, No. 3 (Jul., 1934), pages 500-503. We read this: 

"Dandy has completely removed the right cerebral hemisphere from eight patients. He has performed total extirpations of one or more lobes much oftener... There are tabulated below certain generalizations on the effects of removing the right hemisphere.... The operation was the complete extirpation of the right frontal, temporal, parietal, and occipital lobes peripheral to the corpus striatum. The weight of the tissue removed varies, with the pathological conditions involved, from 250 to 584 grm [grams].Coherent conversation began within twenty-four hours after operation, and in one case on the afternoon of the same day. Later examinations showed no observable mental changes. The patients were perfectly oriented in respect of time, place, and person; their memory was unimpaired for immediate and remote events; conversation was always coherent; ability to read, write, compute, and learn new material was unaltered. Current events were followed with normal interest. There were no personality changes apparent; the patients were emotionally stable, without fears, delusions, hallucinations, expansive ideas or obsessions, and with a good sense of humor; they joked frequently. They showed a natural interest in their condition and future. They cooperated intelligently at all times throughout post-operative care and subsequent testing of function." How could the memory of patients be "unimpaired for immediate and remote events" if memories are stored in brains?

The quote above also refers to the Vining paper I quote from above. The quote also refers to Bell and Karnosh, who in 1949 referred to 4 operations they had done, stating, "In all cases the relative freedom from severe physical handicap and gross mental defect after removal of almost half the cerebrum was striking" (pages 285-286). That is not a quote anyone would make if patients had lost their episodic or learned memories. 

All in all, the results discussed above are consistent with the idea that the human brain is not the storage place of human memories and is not the source of the human mind.  The results are not the results we would get if brains stored human memories and brains produced minds. 

Postscript: In the article here, we read of a doctor who has performed hundreds of hemispherectomy operations.  We get this quote: 

" 'I've had hemispherectomy patients go to college, get married, have children, have a family, and be cognitively completely normal with one side of the brain,' Bingaman said. 'How that happens? We don't understand it.' "

Preservation of Mind and Memories After Removal of Half a Brain

"Scientific journals have reported cases of persons whose injuries have necessitated the removal of a large portion of the brain, and whose memory and power of thought were unimpaired by the loss of much cerebral matter, or by damage to centers which are supposed to be necessary to memory and consciousness. Dr. Troude writes:  'As M. Bergson foresaw in 1897, the hypothesis of the brain as conservative of memory images, must be renounced once and for all, and other ideas as to the nature of its role in the act of memory must be accepted. ' "

--- Helen C. Lambert, A General Survey of Psychical Phenomena, p. 49.

The idea of a crucial experiment or critical experiment is an old concept in the world of science. Such an experiment is supposedly one that leaves one particular hypothesis standing, and rules out all rival explanations or rival hypotheses. The idea that there are such experiments has been criticized by some. A simpler idea is the idea of a sink-or-swim experiment. A sink-or-swim experiment is one that either leaves some hypothesis standing as a viable hypothesis (the “swim” situation) or causes the hypothesis to be discredited (the “sink” hypothesis).

Scientists have very often claimed that the human mind is produced by the brain, and that memories are stored in the brain. A very interesting question is: could you do a sink-or-swim experiment testing such hypotheses? The experiment has actually been done, not just once but many times. I will here use the term “experiment” for medical procedures that were usually done for medical reasons such as stopping very bad brain seizures in patients. Although the doctors who did such procedures may not have considered them experiments, we can consider them as experiments in the sense of testing a particular hypothesis about the brain.

The sink-or-swim experiment for the hypothesis that the brain makes the mind and the hypothesis that the brain stores memories is to surgically remove half of the brain, and see what the effect is on the mind and memory. Such an experiment has been done many times. Almost every time the result has been that there was no major effect on consciousness, no major effect or intelligence, and no major effect on memory. The memories of people who had half of their brains removed usually preserved the knowledge and life memories they had acquired.

This is a “sink” result for this sink-or-swim experiment. The results of such surgical operations decisively refute claims that the mind is the product of the brain and claims that the brain is the storage place of memories. But addicted to materialist dogma that the mind is merely the product of the brain and that memories are stored in brains, virtually no neuroscientists have paid attention to the results of these sink-or-swim experiments. In this regard, they are like fundamentalists who keep believing that the Earth is 6000 years old despite observational results indicating our planet is billions of years old.

I have in five previous posts (here, here, here, here and here) listed very much data relating to such experiments. In this post I will not restate that data showing that intelligence is well-preserved after removing half of the brain, but will mostly cite some data and cases I have not previously discussed.

I can start with the results reported in the American Journal of Psychology, Vol. 46, No. 3 (Jul., 1934), pages 500-503, regarding work of W. E. Dandy, in which he removed half of the brains of patients. You can read the results in the preview here (without doing any registration). We read the following (I have put a few of the sentences in boldface):

“Dandy has completely removed the right cerebral hemisphere from eight patients. He has performed total extirpations of one or more lobes much oftener... There are tabulated below certain generalizations on the effects of removing the right hemisphere.... The operation was the complete extirpation of the right frontal, temporal, parietal, and occipital lobes peripheral to the corpus striatum. The weight of the tissue re moved varies, with the pathological conditions involved, from 250 to 584 grm [grams].Coherent conversation began within twenty-four hours after operation, and in one case on the afternoon of the same day. Later examinations showed no observable mental changes. The patients were perfectly oriented in respect of time, place, and person; their memory was unimpaired for immediate and remote events; conversation was always coherent; ability to read, write, compute, and learn new material was unaltered. Current events were followed with normal interest. There were no personality changes apparent; the patients were emotionally stable, without fears, delusions, hallucinations, expansive ideas or obsessions, and with a good sense of humor; they joked frequently. They showed a natural interest in their condition and future. They cooperated intelligently at all times throughout post-operative care and subsequent testing of function.”

It would be rather hard to imagine a more decisive refutation of the claim that the human brain is the source of the human mind, and the claim that the human brain is the storage place of human memories. Here are eight people who had half of their brains removed. Yet the people showed “no observable mental changes,” and “their memory was unimpaired for immediate and remote events.” The people could read, write, compute and learn just as if nothing had happened, and “there were no personality changes.”

A 1966 paper was entitled “Long-term changes in intellect and behavior after hemispherectomy.” The paper refers to operations in which half of a brain is removed, often to stop very bad brain seizures. This paper gives very detailed “before and after” IQ score data on 11 people who had half of their brains removed. Eight of the 11 people had the left half of their brain removed, and the other three had the right half of their brain removed. Every single one of the 11 people was able to get an improved IQ score on at least one of the tests taken after half of their brain was removed, a score better than a corresponding score they had got before half of their brain was removed.

Patient 1 (a P.G.) had an IQ of 128 before half of his brain was removed. After half of his brain was removed, he scored 142 on an IQ test. The paper tells us that this man with half a brain “obtained a university diploma after operation” and “has a responsible administrative position with a local authority.”

The same paper refers to previous results when removing half of a brain, and notes data suggesting that such an operation has little negative effect on intelligence. Referring to intelligence, we are told that McKissock reported “short term improvement in 13 of 17 cases,” that another researcher found “significant improvement in verbal intelligence scores in a variety of tests after operation in five of 35 cases, with temporary deterioration in two, the remainder unchanged.” We are also told that White “reports improvement in personality in 80% of 134 cases” in which half of the brain was removed.

The 2013 paper "Long-term functional outcomes and their predictors after hemispherectomy in 115 children" reports this: "In this cohort of 115 children, at a mean follow-up of 6.05 years after hemispherectomy, 83% patients walked independently, 73% had minimal or no behavioral problems, 69.5% had satisfactory spoken language skills, and 42% had good reading skills."  These results are for people with half-brains, and we should remember that a large fraction of people with full brains lack good reading skills.  Typically a hemispherectomy operation occurs as a last resort for a child who has been long-plagued by seizures.  Before the operation, such seizures may have long-disrupted normal learning.  So this 42% may not even reflect any major deterioration in reading skills after removal of half a brain. 

In the scientific paper here, we have on page 248 and page 250 before and after test scores for various subjects who had of their brains removed in hemispherectomy operations.  The IQ score differences are slight. IQ tests don't involve learned information, but almost any IQ test would be largely a test of memory, as it would be a largely a test of ability to read test questions.  

On the same pages we have before and after test scores for Peabody Picture Vocabulary Tests given to various subjects who had  half of their brains removed in hemispherectomy operations.   In these tests, someone is shown picture cards like the one below, and asked to name the words represented by the pictures.  These tests are tests of memory retention after removal of half of the brain.  On these memory tests there was no decline in the score of 21 subjects mentioned on page 248, and no decline in 7 subjects mentioned on page 250. 

In an article in the New Yorker magazine, we are told of a Christina Santhouse who had half of her brain surgically removed: “When I met her, she had taken her S.A.T.s and just finished high school, coming in seventy-sixth in a class of two hundred and twenty-five.” If your brain makes your mind, how could you finish in the top 34% of your class with only half a brain? The same article tells us of someone who had half of the brain removed, but made the dean's list in college, a list of the top-performing students on campus.

An article in the LA Times tells us about memory preservation in a young girl who lost half her brain:

“How is it that 8-year-old Beth Usher of Storrs, Conn., can lose her left hemisphere, yet retain her large repertoire of knock-knock jokes? Beth’s memories survived not just the loss of brain tissue, but also the 32 days that she spent in a coma, the result of some brain stem swelling that occurred in response to the trauma of surgery. Shortly after Beth regained consciousness, her father began quizzing her about people and places from her past. Brian Usher didn’t get very far. 'Dad,' Beth interrupted, with a trace of impatience. 'I remember everything.' ”

In a scientific paper ("Why Would You Remove Half a Brain? The Outcome of 58 Children After Hemispherectomy −−The Johns Hopkins Experience: 1968 to 1996") we read about how surgeons at Johns Hopkins Medical School performed fifty-eight hemispherectomy operations on children over a thirty-year period. Eleven of these children had the left hemisphere of their brains removed; most of the rest had the right hemisphere of their brains removed.  The paper states this:

"Despite removal of one hemisphere  [i.e. one half of the brain], the intellect of all but one of the children seems either unchanged or improved....Although there have been major concerns about loss of language after left hemispherectomy, all eleven of these children have regained virtually normal language....It is tempting to speculate, that the continuous electrical activity of these severely dysfunctional hemispheres interferes with the function of the other, more normal hemisphere. This might explain why motor function improves after hemispherectomy and why language recovers after removal of the dysfunctional left hemisphere, but does not seem to fully transfer before surgery. Perhaps it also partially explains intellectual improvement in these children after removal of half of the cortex. We are awed by the apparent retention of memory after removal of half of the brain, either half, and by the retention of the child’s personality and sense of humor."

There is a reason why we can be confident that removal of half of a brain in hemispherectomy operations does not cause any major loss of learned memories.  If there was a case of any such thing happening, you can believe that it would be endlessly recited by those who wish for us to believe that memories are stored in brains.  But there is no such case, so we never hear materialists telling us about some person who suffered some dramatic loss of learned knowledge after having a hemispherectomy operation in which half of his brain was removed. 

Our professors very often make biology claims that are contrary to the low-level facts of biology. The table below lists various cases in which the fantasy biology of academia dogma diverges from biology reality. 

FANTASY BIOLOGY VERSUS BIOLOGICAL REALITY
Dubious Biology Claim	Biological Reality
Brains store memories, probably in synapses or dendritic spines.	Neither synapses nor dendritic spines last for even a tenth of the longest time that humans can remember things, and both are made up of proteins with lifetimes of only a few weeks.
DNA stores a blueprint or recipe for making the human body.	DNA does not specify the physical structure of any of these things: an organism's body, its organ systems, its organs or its cells.
Visible biological innovations arise from a combination of random mutations and natural selection, which improves the DNA of a species.	It has not been proven that any visible complex biological innovation ever appeared because of random mutations and natural selection, and we know of a reason why mere DNA mutations could never produce a complex visible biological innovation: that visible physical structures are not specified in DNA.
Life appeared because of a lucky combination of random chemicals billions of years ago.	Neither a living thing nor any of the building blocks of a living thing (proteins and nucleic acids with genetic information) has ever been produced through any experimental process that  realistically simulated early Earth conditions.
The building blocks of life have been found in outer space.	No one has found in outer space either of the two actual building blocks of life: proteins or nucleic acids with genetic information.
Brain scans show your brain makes your mind.	Brains scans actually show signal differences of less than 1% during thinking or recall, what we would expect from random variations.
Brain signals are real fast.	Synaptic delays, synaptic fatigue and relatively slow dendritic transmission mean that signals in the cortex must be real slow.
The common descent of all life from a single ancestor is a fact.	A shortage of transitional fossils and the lack of DNA corresponding to old fossils (because of DNA's half-life of 521 years) make the doctrine of common descent very unproven.
Chemically humans are almost exactly like chimps.	80% of proteins are different between humans and chimps.
Our minds can be explained neurally.	There is no credible neural explanation for any of the main features of the human mind: memory, self-hood, consciousness, abstract thinking, and imagination.
We kind of understand how a speck-sized egg can progress to become a full-sized baby.	We have no understanding of how this occurs (given a lack of a body plan in DNA), and do not even understand what causes cells to reproduce.
Memory and intelligence depend strongly on brain status.	A person can lose half of his brain in a hemispherectomy operation, with little effect on memory or intelligence.

The image below reproduces the table above. 

Postscript: The paper "Language recovery after hemispherectomy in children with late-onset seizures" gives us before-and-after IQ scores for six children having removal of the left half of the brain (Table 1, FSIQ row). Such comparisons can be affected by short-term deficets that later are reduced. The comparison shows one child dropped 20 IQ points, one child dropped 10 IQ points, another child gained 3 IQ points, another child dropped 15 IQ points, another child gained 11 IQ points, and another child had no change in IQ. The very mixed results are consistent with the brain not being the source of the human mind. 

On page 254 of the textbook here, we read a statement by someone saying that he performed 43 hemispherectomy operations. He says, "The secondary outcome scores reevaluated at six months and 1 year showed no significant difference in IQ," indicating intelligence is not affected by removal of half of the brain. 

Page 5 of the scientific paper here describes a 7-year-old girl who is "fully bilingual in Turkish and Danish" despite having had most of half of the left side of her brain removed in a hemispherectomy operation at the age of 3. We are told that except for a slight spasticity, "she leads an otherwise normal life." 

On page 3 of the Florida newspaper you can read here, the Lake City Reporter of December 25, 2015,  we have a quote by brain surgeon Ben Carson:

"He recalled meeting one patient to whom he’d

given a hemispherectomy — removing half the brain

— as an infant. 'He had graduated from college

number one in his class — with half a brain,' Carson

said." 

Below is an excerpt from the 1931 newspaper article "How Much Brain Used?" by William Brady M.D.:

"Aside from the fact that the boy felt no pain from the surgical treatment (and had no anesthetic), it was remarkable that he retained full consciousness and unimpaired mental function, al| though a considerable part of the cerebrum was destroyed. Recent surgical observation has proved that the whole of the right cerebral hemisphere may be removed without disturbance of mentality: this has been done repeatedly for the removal of large brain tumor. Both right and left frontal lobes of the brain may be removed without disturbing the patient's mentality. The patient remains perfectly oriented as to time, place and person; the memory is unimpaired: reading. writing and mathematical calculation are still done accurately; conversation is normal. In other cases the left occipital lobe and the lower third of the left temporal lobe have been removed without apparent. effect on mentality. "

You can read the full article using the link below:

https://chroniclingamerica.loc.gov/lccn/sn83045462/1931-01-20/ed-1/seq-28/

Below is the first page of a 1933 Popular Science article written by a doctor, one you can read here. We are told of a woman who had the "entire right half" of her brain removed. We are told that a few hours after the operation she "recognized and talked with her friends." The operation apparently caused no loss of learned knowledge or memories.  Both the act of recognizing a friend and the act of talking requires the use of learned knowledge such as the knowledge of what a friend looks like, and the knowledge of the words in a language and the grammar rules of the language. We are told the woman "improved rapidly, reading and writing during her convalescence." No mention is made of any loss of memory.  The reported result is consistent with the idea that the brain does not store memories. 

The next page mentions several case histories of people who suffered the most horrible brain injuries in various types of accidents. No mention is made of any damage to memory or mind. We hear instead comments such as "apparently his mind did not suffer from the accident" and mention of a "miraculous recovery."

Another case is discussed here, in a book chapter of a textbook. We read of a patient E.C. who had a large brain tumor. To treat the tumor, the left half of the patient's brain was removed, in a hemispherectomy operation. We read that "the entire hemisphere was removed in one piece" on December 7, 1965. We read that "immediately following hemispherectomy" the patient had an "ability to follow simple verbal commands."  We read on page 107 that "the patient spontaneously articulated words and short phrases fairly well immediately after the operation."  

We read that this patient E.C. "gave the correct number of years when asked how long he had lived at his house." We read on page 107 that on January 26, 1966 (about six weeks after the operation) he "slowly but correctly selected four of the first six items from six pages, each with four items to choose from, before indicating he was tired" when given the Peabody picture vocabulary test. Such a test involves a tester speaking a word, and the user pointing to the correct picture in a grid of 4 pictures. 

The image below (from the paper here) shows an example of one of the pages. The word spoken by the tester is "citrus."

The result described above (4 out of 6 correct on six such pages) clearly suggests that patient E.C. retained his learned knowledge after the left half of the brain was removed. Since the test was given only six weeks after the operation, and E.C. was in a recovering state during those weeks in which he was not being schooled, we cannot explain such a result as being due to knowledge acquired during those six weeks. We also read on page 107 that on June 3, 1966 patient E.C. correctly named 85 out of 112 items on such a Peabody picture vocabulary test. No mention is made of schooling occurring during the first six months of 1966. 

On page 109 we read of three other cases of the removal of the left half of the brain, and we read that "speech and verbal comprehension were present immediately after left hemispherectomy in all three cases." We read nothing about any loss of knowledge or episodic memories in any of these cases.  Neither speech nor verbal comprehension can occur unless a great deal of learned knowledge is retained. 

The news story here documents a very clear case of the preservation of memory after the removal of the left half of the cerebrum. We read of a 47-year-old man who had the left half of his cerebrum removed. We read this:

"Dr. Smith said the patient's memory of events before the operation 'was well preserved, much better than anyone expected.' Tests following surgy show Coe can perform many functions traditionally thought impossible after removal of the brain's dominant hemisphere. Immediately following surgery, Coe still had the ability to speak spontaneously."

A report like this does not merely contradict the claim that the brain is the source of the mind. It also contradicts the claim that the brain is a storage place of memories. 

The 1963 newspaper account here is entitled "Monkeys With Half a Brain." We read this:

"Fifty monkeys have had half of their brains removed. Their memories appear to be as complete as before surgery. Until this experiment was made, even doctors thought that such surgery would affect memory....Not only is memory retained; the monkeys are alert, intelligent, sociable, and have the same enthusiasm as doing things as before....What are some of things the team has discovered from observation of monkeys with half their brain removed? The monkeys remember how to do things taught them before surgery. Such as which of two blocks of wood place under them has a reward under it -- a raisin or other food. Fears are recalled....'While the rhesus monkeys we test remember everything taught them before surgery, it takes them twice as long to learn something new as monkeys with both half of their brain,' explains Dr. Kruper. 'But the important thing is that they DO learn, even if it does take them longer.' "

The visual below "speaks volumes" on this topic. It is the result of a search on Google Scholar for "amnesia after hemispherectomy." "Hemispherectomy" is the standard name for the operation that has been performed thousands of times, in which half of the brain is removed to stop very bad seizures. "Amnesia" is the main term used for a loss of episodic memories.  Any search on Google Scholar will produce very many results when there are quite a few cases corresponding to such a search. For example, doing a Google Scholar search for "vision loss after automobile accident" produces many results. But doing a search for "amnesia after hemispherectomy" produces zero results.

The results discussed in this post deserve to be pondered at great length. The results indicate very strongly that the human brain is not any storage place of human memories. After considering such results, you should also ponder the most important null result of neuroscience research: the fact that brain tissue from thousands of living and recently deceased humans has been microscopically studied at great length, with the most powerful microscopes; but no one has ever found the slightest trace of learned information or any episodic memory by such microscopic examination. No one found a single phrase, a single word or even a single letter of the alphabet after microscopically examining brain tissue. Nor did anyone ever find by microscopic examination of brain tissue any trace of anything a human ever saw or heard.