One way to test the "brains make minds" hypothesis is to examine the effect of brain tumors on cognitive performance. Under the hypothesis that the brain makes the mind and the brain stores memories, we should expect brain tumors to have a huge effect on cognitive performance. That does not seem to be the case at all.
The most common test of cognitive performance used by doctors is a test called the MMSE, which stands for the Mini Mental State Examination test. The link here gives you some of the questions used on the test. An example question is that you are asked to count backwards from 100, going back 7 in each steps (for example, 93, 86, 79, 72, and 65). The MMSE test has a maximum score of 30. Adults with normal cognitive functions will tend to score about 29 on the test. The link here says that a score of 24 or higher is considered "normal."
Another widely used test of mental function is the Raven's Colored Progressive Colored Matrices test, called the RCPM. The test has a maximum score of 36. According to the paper here, an average score for an elderly person is about 26.
The study here ("THE EFFICACY OF RAVEN’S COLORED PROGRESSIVE MATRICES FOR PATIENTS WITH BRAIN TUMOR") gives MMSE and RCPM scores for 43 patients, before and after surgery for a brain tumor. We read about some remarkable results: "Median pre- and post-operative MMSE scores were 29 points (14–
30) and 29 points (21–30), respectively. Median pre- and post-operative RCPM
scores were 33 points (25–36) and 35 points (18–36), respectively."
Let us consider how much this result contradicts the "brains make minds" dogma. The results for the Mini Mental State Examination (MMSE) test were almost perfect for the 43 subjects with brain tumors. They scored a median of 29, only one point less than a perfect score of 30. For the Raven's Colored Progressive Matrices test, the median score of the brain tumor patients after brain surgery was an almost perfect score of 35, only one point less than the maximum of 36. Moreover, after the brain surgery the score for these patients improved from 33 to 35. Nothing is done in a brain tumor surgery to cognitively fix a brain. The sole purpose of the surgery is to remove the cancerous tumor, hopefully in some way that will prevent the tumor from reappearing. Very often the amount of brain tissue removed is greater than the amount that looks grossly cancerous. Under the hypothesis that the brain makes the mind, we should not at all expect patients to be getting better scores on mental tests after they had surgery to remove a brain tumor.
Another interesting study is the study "Cognitive reserve and individual differences in brain tumour patients." The study involved about 700 brain tumor patients who were cognitively tested. The patients included 143 low-grade glioma patients, and 181 high-grade glioma patients. High-grade glioma patients are those with really bad brain tumors. The study has the limitation that it fails to give us the average or median cognitive test scores that it analyzed. All that we are given is some analysis expressed by using correlation coefficients. A correlation coefficient is a number between 0 and 1 telling us about how much one thing is correlated with another. A correlation of 0 indicates no causal relation, and a correlation of 1 indicates a perfect causal relation.
Table 4 of the study indicates there was virtually no correlation between the volume of the tumor and performance on the Raven's Colored Progressive Matrices test, a negligible correlation of only −0.0345. The same table indicates there was virtually no correlation between performance on the Raven's Colored Progressive Matrices test and whether the tumor was a high-grade glioma, a negligible correlation of −0.0310. We see a much higher correlation of .349 for "fronto-parietal" tumors, but Table 1 says there were only six patients with "fronto-parietal" tumors, so it's too small a sample size of "fronto-parietal tumor" patients to be very significant evidence.
Table 3 of the paper here ("Pre-Surgery Cognitive Performance and Voxel-Based Lesion-Symptom Mapping in Patients with Left High-Grade Glioma") gives the results of cognitive tests on 85 people with high-grade glioma in the left hemisphere. Under the dogma that the brain makes the mind, we would expect most of these people with severe brain tumors to have performed poorly on such tests. But the table does not show that. Instead we see that on 17 out of 18 tests most of the patients did not perform in a "pathological" manner. Only on a "verb naming" task did most of the subjects perform poorly, with 61% performing poorly. On 17 out 18 tests an average of only about 25% of the subjects performed poorly.
The paper here ("Quality of life in patients with stable disease after surgery, radiotherapy, and chemotherapy for
malignant brain tumour") analyzed cognitive data on 57 brain tumor patients with malignant brain tumors, a particularly severe type. We read this: "Separate Mann Whitney tests did not show any differences between the tumour and control groups in terms of score for FLIC (U=476.5, p=0.031), ADL (U=674, p=0.89), STAI1 (U=502, p=0.059), STAI2 (U=641, p=0.65), SRDS (U=618, p=0.49), Raven’s coloured progressive matrices (U=533, p=0.11), attentional matrices (U=624, p=0.53), trail making test part A (U=673.5, p=0.91) and B (U=624, p=0.53), or story recall scores (U=637, p=0.62)." The average score on the Raven’s Colored Progressive Matrices test for the brain tumor patients was about 28 (27.86). The patients with severe malignant brain tumors scored higher than control subjects on this test, who got an average score of only 26.0. According to the paper here, an average score for an elderly person is about 26. So the people with the malignant brain tumors (a particularly severe type) scored higher on the cognitive test than normal people of their age.
The paper here ("Evaluation of mini-mental status examination score after gamma knife radiosurgery as the first radiation treatment for brain metastases") gave the MMSE cognitive test on 119 patients before and after treatment for brain surgery. We read, "In 16 of 37 patients (43.2 %) with pre-GKS MMSE scores ≤27, the MMSE scores improved by ≥3 points, whereas 15 of all patients (19.7 %) experienced deteriorations of ≥3 points." It sounds like the number of increases in cognitive scores was as high as the number of decreases.
The study here ("Episodic Memory Impairments in Primary Brain Tumor Patients") studied problems with memory in 158 people having brain tumors. Using a method that sounds as if it was trying to report as many people as possible as having memory problems, the study claims that only 42% of those with brain tumors had any memory problems. It reports that "No correlations between specific tumor locations and types of episodic memory impairment were found, except for the association of encoding deficits with corpus callosum infiltration (Logistic regression: OR 4.36, β = 1.68, 95% IC 1.37–12.58, p = .02)." Since the people with brain tumors are typically old people, and maybe something like 40% of old report report some type of memory problem, we have no clear evidence that brain tumors are causing memory problems. This study follows a frustrating methodology in which it refuses to report the degree of dysfunction in any of the people reported as having memory problems. We have a claim about what percentage of brain tumor patients have some kind of memory problem, without any details on how bad such problems were. This is just what we would expect if only tiny performance differences were found.
We get a "memory problem criteria" description that sounds like it is trying to place as many people as possible in a category of "people with memory problems":
"Each of the nine scores recorded (number of word recalled at immediate recall), free
recalls (1, 2, 3, delayed) and cued recalls (1, 2, 3, delayed) were considered abnormal when it corresponded to a performance
equal to or under the fifth percentile of the healthy controls normative data (van der Linden et al., 2004). An encoding deficit
was diagnosed when the immediate recall was abnormal (the assumption being that the items were not present in the working
memory immediately after they have been red, and so not encoded). A failure in free recalls corresponded to at least 2/4
abnormal scores and a failure in cued recalls corresponded to at least 2/4 abnormal scores (the test is composed of four free
and four cued recalls). A storage deficit was diagnosed in the case of a failure in free recalls associated with a failure in cued
recalls. This means that the cues didn’t improve the number of items recalled, assuming that the items was not stored. A
retrieval deficit was diagnosed in the case of a failure in free recalls isolated (normal cued recalls). Indeed, the cues improved
the number of items recalled comparably to healthy controls, giving a proof that items was stored in the memory but not available at the moment. Furthermore, an association of storage and retrieval deficit was diagnosed in the case of a failure in free
recalls and a failure in cued recalls, but with limited improvement (incomparably to healthy controls) of the total number of
items recalled with cue."
Despite this method, which sounds as if it was designed to make as many as possible be categorized as people with a memory problem, only 42% of those with brain tumors were classified as having a memory problem. We are left here with no good evidence of brain tumors causing substantial memory problems. The finding that "no correlations between specific tumor locations and types of episodic memory impairment were found" (with only one minor exception) is consistent with the idea that memories are not actually stored in brains.
Another study of 121 patients with severe brain tumors (Stage III and Stage 4) gave four tests of working memory and two tests of episodic memory, finding that only 10%, 17%, 22%, 23%, 28% and 18% had a "clinically relevant deficit." Referring to radiation therapy to treat brain cancer, the paper "Effects of Radiotherapy on Cognitive Function in Patients With Low-Grade Glioma Measured by the Folstein Mini-Mental State Examination" says that "Only a small percentage of patients had cognitive deterioration after radiotherapy."
The study "Efficacy and Cognitive Outcomes of Gamma Knife Radiosurgery in Glioblastoma Management for Elderly Patients" studied 49 patients with the most severe type of brain tumor, a glioblastoma. Table 1 tells us the patients had a median tumor size of 5.4 centimeters (about two inches). According to Table 2, a year after radiation therapy, the average MMSE score of the patients was about 25, slightly below average, but still pretty good. Before the surgery, when the patients had lost a lot of their brain tissue due to tumors, the average MMSE score was a fairly good 27 (30 being the highest score possible).
The study "Detrimental Effects of Tumor Progression on Cognitive Function of Patients With High-Grade Glioma" is one of those studies that makes it hard to extract the most relevant data from it. The most relevant fact that I can extract from it is found in Table 1, where I see that the number of patients with very bad brain tumors (high-grade glioma) and normal cognitive scores (as tested by the MMSE) was 757, and the number with abnormal MMSE scores was only 389. 659 of these 757 patients with normal cognitive scores had Grade 4 brain tumors, the worst type.
The paper "Prospective memory impairment following whole brain radiotherapy in patients with metastatic brain cancer" gives us the MMSE cognitive test scores for 81 patients before and after they had treatment for metastatic brain cancer. The average score before the treatment was 27, and the average score after the treatment was 26 (Table 2). So there was no big difference. The link here says that a score of 24 or higher on the MMSE is considered "normal." According to Table 1, 23 of the patients had a brain tumor larger than 3 centimeters (1 inch).
Below is a quote from the paper "Meningiomas and Cognitive Impairment after Treatment: A Systematic and Narrative Review." The paper summarizes other papers studying the cognitive effects of a common type of brain surgery. The quote below refers to studies that compared cognitive function before and after brain surgery. We see some studies discussing a negative cognitive effect, but relatively few. The reported fractions are not very high. There is also reference to a number of studies showing improvements in cognitive abilities after brain surgery.
"Worsening of verbal, working and visual memory (9/22 studies)
Worsening of complex attention and orientation (1/22 studies)
Worsening of executive functioning (3/22 studies)
Worsening of language and verbal fluency (2/22 studies)
Worsening of cognitive flexibility (4/22 studies)
Worsening in all neurocognitive domains (1/22 studies)
Improvement in verbal, working and visual memory (3/22 studies)
Improvement of complex attention and orientation (3/22 studies)
Improvement of executive functioning (2/22 studies)
Improvement of cognitive flexibility (1/22 studies)."
The same paper summarizes studies comparing those who had brain surgery with normal control subjects. We seem to have only scanty evidence of worse performance after brain surgery, because the reported fractions are low:
"Worse verbal, working and visual memory (2/22 studies)
Worse complex attention and orientation (1/22 studies)
Worse executive functioning (1/22 studies)
Worse language and verbal fluency (2/22 studies)
Worse cognitive flexibility (4/22 studies)."
The fractions quoted are small fractions such as 5% or 10%, and we don't know how much of a decline the "worse" refers to. When you also take into account that neuroscientists will typically be biased towards reporting declines in function after brain surgery rather than improvements or no differences (in accordance with their dogma that brains produce minds), it is not clear that we have here any very clear evidence of decline in cognitive function after this type of brain surgery.
Below is a very notable case of the almost complete destruction of a brain by a brain tumor, but with a high preservation of mental function. It comes from page 71 of the document here (and the newspaper story here repeats the same details).
Overall, these results are quite compatible with the idea that you brain does not make your mind, and the idea that your brain is not any storage place of your memories.
I can recall a personal experience here. Years ago I traveled to see a beloved relative who died by the spread of metastatic breast cancer. When I met her I saw a very noticeable tumor protruding from her head. I seem to recall the skull protrusion being about the size of a fist, or nearly as large. I can assume that a very large part of the brain had been destroyed by the cancer. But when I talked to her, I could notice no change in her cognition. I asked her an important question about events in the past, and she gave a meaningful, detailed answer with relevant examples provided. I left, and a few weeks later she died. The lack of disturbance in cognition, speech and recollection in someone with a very visually noticeable brain tumor was striking.
No comments:
Post a Comment