Hyperthymesia, or highly superior autobiographical memory (HSAM), is a rare condition enabling individuals to recall specific past events with extreme detail, affecting about 20 people globally. Those with HSAM have distinctive memory traits, such as spending more time recalling personal history and remembering over 200 events in a year, unlike the typical 8 to 11 events. The neurological basis of HSAM suggests an enlarged temporal lobe and involves complex memory formation processes, with some individuals perceiving their ability as either a gift or a burden.

1. By:
Srikar Bhimmanapalli
Understanding the Brain:
The Neurobiology of Everyday
Life

2. What is Hyperthymesia?
Hyperthymesia (otherwise mentioned as Highly Superior Autobiographical
Memory, or HSAM) is an extremely rare condition that gives an individual the
abnormal ability to recall any specific event from their own past with
extreme detail, given a date. There are currently around 20 people in the
world with confirmed hyperthymesia.
For example, when given any date from their life following adolescence (say,
July 7, 1984) a hyperthymestic can remember, with vivid detail, what
happened to them or what they were doing that day, whether it was
watching a T.V. show, or visiting San Francisco for the first time. They can
also recall what they were wearing, what they were eating, facial
expressions, emotions, and other episodic details from that day.

3. 3 Distinct Characteristics
There are 3 things that define HSAM:
● They tend to spend a greater amount of time recalling personal history
compared to most people.
● They have an abnormal ability to remember specific events from their
own past more clearly than most people.
● Hyperthymestics can remember over 200 events in the span of a given
year, while most people generally remember around 8 to 11.

4. Important Facts
● Hyperthymesia is much different from photographic memory. Hyperthymesia is
considered having an extremely detailed autobiographical memory, while photographic
memory is remembering facts and figures as well as autobiographical events. Even
though their ability can be helpful, hyperthymestics can indirectly apply their condition to
better themselves at schoolwork, but not in the same way photographic memory
theoretically can.
● It is important to note that individuals with HSAM do not purposefully try to remember
personal events. They do not use mnemonics or other memory devices to remember
things. They are described as involuntary episodes that come automatically.

5. How it feels like to have HSAM
● Every person with HSAM interprets their condition in a different way. Some
are able to organize these memories so they are not reminded of them
every moment, but some still feel it as as a constant burden. For example,
Jill Price describes it as being “haunted by the neverending stream of
memory”. Nonetheless, most hyperthymestics are glad of their gift.

6. Parts of the Nervous System that are Active in HSAM
● Hippocampus and the Temporal Lobe
The hippocampus plays a great role in converting working memory to declarative
memory. Semantic memories are stored within the neocortex, and episodic
memories are stored in the neocortex as well. However, in order to recall
episodic memories, they would need to come back to the hippocampus. This
“episodic loop” renders episodic memories even more labile and easier to forget
each time it goes through the loop. Hyperthymestics seem to lack this
forgetfulness trait for autobiographical memory. In fact, researchers found a
significantly enlarged temporal lobe, containing the hippocampus, when doing
an MRI on one patient.

7. Apparent Functions of HSAM
The memory formation circuitry is an apparent function of HSAM. Even
though it is unclear exactly how hyperthymestics are able to retain such a large and
detailed autobiography, it has been proposed that information retrieved by
hyperthymestics is semantic, but is interpreted as episodic. However this memory
automatically reminds the individual of another memory, and another memory, and so
on, called spreading activation. This is why so many people with hyperthymesia remark
how one memory triggers another, and so on, and how they are powerless to stop it.
Another theory to explain hyperthymesia is that it is caused by individuals
reviewing memories to an obsessive-compulsive degree. This is less satisfying than
other theories, however it explains why the caudate nucleus as well as the temporal
lobe is significantly enlarged. The caudate nucleus is theorized to be involved in
obsessive-compulsive disorder, among other things (executive function, memory, slow
wave sleep). It is located in the basal ganglia.

8. How this Course has Helped Me
While learning this course, I was able to give connections of
everyday activities to functions of the brain. Everything I did finally had a
neurological reason behind it. Also it was good to be able to basically learn
more about the world we live in, and terminate any suspicions I had. This
course also sparked a new interest in me, which I will follow to learn more.
Using the knowledge from this course, I can better myself at
ordinary tasks, as well as new ones. But most importantly, this course has
given me the basics of neurobiology, as well as the opportunity to learn more
about a much more complex and intriguing subject of science.

9. References
● http://www.webpronews.com/marilu-henners-amazing-memory-inspired-new-
book-2012-04
● http://www.ncbi.nlm.nih.gov/pubmed/22519463
● http://en.wikipedia.org/wiki/Hyperthymesia
● http://www.ncbi.nlm.nih.gov/pubmed/24248358
● http://www.mylifememory.info/
● Henner, Marilu. Total Memory Makeover. Gallery Books, 2013
● http://en.wikipedia.org/wiki/Caudate_nucleus#Cognitive_Functions