She Has the Most Astounding Memory Skills But a Smaller-Than-Average Hippocampus

The explanations of neuroscientists lack very many things. For example, they lack:

• Any coherent or credible theory of how a brain could convert experience into brain states or synapse states when a memory is created;
• any coherent or credible theory of how a brain could convert brain states or synapse states into thoughts or recollections when a memory is recalled;
• any coherent or credible theory of how a brain could instantly create new memories, something that humans routinely do; 
• any coherent or credible theory of how a brain could instantly retrieve a memory, such as getting instantly getting just the right answer when someone is asked to identify some person or object or technical term or historical event;
• any coherent or credible theory of how a brain could create an abstract idea such as the idea of a child or the idea of a dog.  
• any coherent or credible theory of how a brain could imagine something such as some invention no one ever built yet. 

A standard approach of the writers about the brain is to use the trick that can be described as: when you don't have a how, try using a where. For the typical writer about brains, this involves making claims of localization of brain activity.  For example:

• When they don't have a "how" in regard to the brain and abstract thought, they try using a "where" by claiming that abstract thought comes from the frontal cortex. This claim is very dubious because of evidence I discuss in my post "Reasons for Doubting Thought Comes from the Frontal Lobes or Prefrontal Cortex" you can read here.
• When they don't have a "how" in regard to the brain and memory, they try using a "where" by claiming that the hippocampus drives the wonders of memory. This claim is very dubious because of evidence I discuss in my post here. A key element of false claims about the hippocampus and memory is the claim that patient HM could not form new memories after his hippocampus was surgically ravaged. The claim that this patient could not form new memories after  such damage is untrue, as I show in my post here. 

People have been so conditioned to think that the hippocampus is crucial for memory that you can predict exactly what a typical reader of brain-related articles might say after reading this quote from a paper on the astonishing case of subject RS: "RS’s recall of past events appears profoundly rich in episodic detail, including associated tastes, smells, emotions, interactions with others, as well as more trivial details that others would likely forget (e.g., weather conditions). As mentioned above RS... apparently remembers the entire text from all seven Harry Potter novels." Hearing of  such amazing memory abilities far beyond the memory performance of almost everyone, a typical person might say something like: "Wow, she must have a really big hippocampus!"

But the astonishing subject RS actually has a hippocampus well-below average in size. 

The case of subject RS is described in the paper "Enhanced semantic memory in a case of highly superior autobiographical memory" which you can read here. The title refers to Highly Superior Autobiographical Memory or HSAM, a very rare ability in some people to recall  very well with extraordinary accuracy events and detail events in their lives. Such subjects are discussed in my posts here:

HSAM Memory Whiz Subjects Scored 25 Times Higher on a Random Dates Test

HSAM Wonder Daniel McCartney Was a Math and Memory Marvel

The Rare "Total Recall" Effect That Conflicts with Brain Dogmas

The paper describes the young subject RS in this way: 

"RS has vivid autobiographical memories that apparently arise automatically. At the same time, she describes her memories as being organised sequentially, so that to retrieve an event she mentally 'scans'  an ordered structure starting from the earliest memory and continuing to more recent memories until the correct entry is found, akin to scanning a mental timeline (Price & Mattingley, 2013)."

This is a striking description that seems to describe memory working different from the way memory works with the average person.  The paper says this about subject RS:

"The first source of her superior memory involved being able to name days of the week for any given calendar date since the year 2000 (e.g., 'What day was it on 2 March 2002?' Answer: Saturday). The second involved her seeming ability to remember the entire text, practically word for word, of the seven books of the Harry Potter series by J.K. Rowling."

Those who have studied the most impressive examples of human memory performance will recognize the calendar ability described, which is typically called "calendar calculating" (although it can occur so quickly that it seems beyond any explanation of calculation, as confessed in the scientific article here).  It has long been known that some humans have an extraordinary ability to accurately name the day of the week given a very old random date from years ago. Such people may be called "human calendars" or "calendar calculators."  One of the most famous examples is Kim Peek, the autistic savant who inspired the Tom Cruise movie Rain Man. At the 2:31 mark of the extremely interesting video here, we see an example of Kim Peek's calendar ability. At that part he is asked by the adult Daniel Tammet what day of the week was Daniel's birthday of January 31, 1979. Within five seconds Kim correctly answers that the date was a Wednesday.  The same ability was proven to exist as early as the 19th century. My post here on the case of Daniel McCartney quotes an interview in which a reporter repeatedly asked Daniel what day of the week corresponded to some random date the reporter selected, with the dates spanning many decades.  Daniel would give the correct date of the week very quickly when asked such questions, just as if no calculation was involved. 

To test the calendar calculation abilities of subject RS, the paper authors devised a test in which a computer screen would ask 60 times a question like this (with the dates varying in each of the 60 trials): "Which date is earlier in the week:  25 September 2005 or 2 March 2005?"  Answering a question like this at levels above chance requires two different successes in the mysterious "calendar calculating" ability, one that might yield the day of the week for the first date, and another that might yield the day of the week for the first date. The performance of subject RS on this task was compared to that of 10 controls, ordinary people with no special memory ability. 

This was the result of the experiment, verifying that subject RS did really have the ability of being able able to tell the day of the week corresponding to randomly selected dates:

"Overall mean accuracy for determining the earlier date within a week was 90% for RS (SD = 0.30) and 50% for controls (ranging from 43% to 55%; SD = 0.50). Overall median reaction time was 17.12 s for RS (SD = 7.01) and 1.24 s for controls (ranging from 0.51 to 18.85 s; SD = 10.64). Controls responded quickly because they were only able to guess on this task, unlike RS who deliberated carefully and was correct on 9 out of 10 trials."

So in 62 trials subject RS answered 90% correctly when asked questions such as "Which date is earlier in the week:  25 September 2005 or 2 March 2005?" -- a type of question that requires "day of the week" remembering or "day of the week" calculation for two random dates. The control subjects scored only at the chance level of 50%.

To test how well subject RS could recall text from the Harry Potter series of books, scientists had RS and some control subjects attempt to answer 30 questions such as the one shown below, which has quotes from a particular book in the Harry Potter series of books. 

The control subjects presumably all had knowledge of the Harry Potter series of books much better than the average person, because they are described in the paper as "aficionados of the Harry Potter series." The results were that subject RS got 97% of the 30 questions correct (29 out of 30), while the control subjects got 71% correct (better than the by-chance expected value of 50%, because the control subjects were aficionados of the Harry Potter series). The almost-perfect result of patient RS in this experiment tends to back up the author's claim that she had a "seeming ability to remember the entire text, practically word for word, of the seven books of the Harry Potter series by J.K. Rowling."

So we have in this subject RS several types of astounding memory ability, with RS having memory abilities of breathtaking power.  The same subject had an MRI scan of her brain. Did it reveal some anatomical anomaly that can explain the supernormal memory ability? Not at all.

Referring to regions of interest (ROIs0), which in this case means parts of the brain, the paper says, "High-resolution structural MRI scans revealed no volumetric or cortical thickness differences between RS and controls within any of the expected ROIs (i.e., hippocampus, amygdala, insula, temporal gyri and pole, subiculum, putamen)." In other words, she did not have some unusual brain anatomy that can explain her memory skills. 

In fact, the measured volume of the hippocampus of subject RS was below-average. The scientific paper tells us the total volume of her hippocampus (the sum of the volume on her hippocampus on the left side of her brain and the  hippocampus on the right side of her brain) was 4.731 cubic centimeters.  The scientific paper "HIPPOCAMPAL VOLUME AND SHAPE ANALYSIS IN AN OLDER ADULT POPULATION" attempted to judge the size of the hippocampus in 40 elderly adults.  Using "cc" to mean "cubic centimeters," the paper tells us this:  "Total ICV-adjusted volumes were 3.48 cc (±0.43) for the left hippocampus and 3.68 (±0.42) for the right hippocampus." That gives a total hippocampus volume of 7.16 for these 40 people.  Subject RS had a hippocampus volume of 4.731 cubic centimeters, so her hippocampus was smaller than average. The same scientific paper tells us this: "There were no significant correlations between ICV-adjusted hippocampal volumes and age or memory performance (p>.05)."

So it seems we should not be surprised at all that this woman with the miracle memory had a hippocampus of below-average size, simply because there is no basis for any claim that hippocampus size has any major relation to memory performance, contrary to the misleading insinuations of people writing about the hippocampus.  

The term "hyperthymesia" is another term used for HSAM or Highly Superior Autobiographical Memory. A recent paper is entitled "Autobiographical hypermnesia as a particular form of mental time travel." In the abstract we read this:

"Here, we describe a case of hyperthymesia with an objective as well as a subjective assessment of mental time travel abilities in different temporal distances. This is the first observation of hyperthymesia with a full evaluation of mental time travel capacities in different temporal distances, encompassing the individual capacity to retrieve personal events from the personal past as well as to foresee personal events in the future."

Unfortunately the paper is behind a paywall. But an article on the story summarizes some of its details:

"The study focused on a 17-year-old girl, referred to as TL, who organizes her memories with unusual precision. She separates her memories into two types: ‘black memory,’ which is factual information learned in school without emotional significance, and her autobiographical memories, which she stores in a detailed mental framework.

TL describes her autobiographical memories as being stored in a ‘white room,’ where binders are organized by theme and date. In this mental space, she can review episodes from family life, vacations, friendships, or childhood experiences. Some memories are recalled as images or text messages."