What causes hyperthymesis in the human brain

An almost perfect memory

Transcript

1 psychology hyperthymesis An almost perfect memory A handful of people in the world have detailed memories of almost every day of their lives. By looking into their brains, researchers want to find out how the miraculous ability comes about. By Daniela Zeibig At a Glance Day after day, researchers report 1 on isolated cases of people who have an amazingly precise autobiographical memory. The memories 2 involuntarily impose themselves on those affected who are otherwise normally intelligent. The cause are 3 possibly particularly intensive connections in the brain. Briefly explained The term hyperthymesia combines two terms from the Greek: The prefix "hyper" means "about", "thymesis" stands for "memory". You can probably still remember what you had breakfast that morning. But do you also remember what was on your menu on November 23, 2003? Some people in the world can actually answer this question with ease. Their memory is so remarkable that from some point in their childhood or adolescence they will remember each and every day in detail. They still remember exactly what day of the week a date fell, what they did that day and what was in the newspaper at the time. Scientists refer to this phenomenon as hyperthymesia or "highly superior autobiographical memory" (hsam) in German: far superior autobiographical memory. To this day, however, experts have been puzzling as to where the outstanding memory comes from. Research into it turned out to be particularly difficult because, to date, very few people are known to have an almost perfect autobiographical memory. The history of the syndrome begins with the fall of Jill Price (see also GuG 1-2 / 2010, p. 14). In 2000, the American turned to James McGaugh of the University of California at Irvine for help. In one, she describes her unusual abilities to the researcher: Her first memories date back to when she was still a toddler, and every single day has stuck in her mind since February 5, 1980. She does not consciously evoke thoughts of her past, but is literally overwhelmed by them when she comes across a date somewhere. Some may dream of such a gift, but Price finds it an extremely burdensome burden. Fascinated by her case, McGaugh examines Price's extraordinary memory for the next five years. In numerous intelligence and memory tests, he repeatedly queries your knowledge of individual days from the past. It turns out that Price's memory is particularly noteworthy when it comes to calendar dates. For example, she can correctly enumerate all Easter days between 1980 and 2003 within ten minutes, but she is wrong by two days in one appointment. Apparently she also knows what happened in her life on those days. McGaugh and his team find part of this information in Price's diary, which they have kept meticulously since their puberty. The woman with the miraculous memory can also remember public events with the day and date, provided that she was personally interested in them. At one point, the researchers test them with a book listing special events in recent American history. 26 GuG 4_2013

2 pot with mashed potatoes: dreamstime / Viktorfischer; George W. Bush: dreamstime / Loon Creative; Tanks: dreamstime / Daniel Raustadt; Sun: fotolia / Sandra Cunningham; Concorde: istockphoto / Getty Images / Sion Touhig; Composing: Brain and Mind June 13th November Bush becomes US President June Gulf War begins January 16th last Concorde flight Do you remember? What has been done on any day in the past, very few of us remember, even if it is a historical date. People with hyperthymesis, on the other hand, have a much more detailed autobiographical memory. November

3 psychology hyperthymesis Famous case The American Jill Price is considered to be the best-studied person with a hyper-accurate autobiographical memory. Briefly explained Neuropsychologists describe those mental processes that serve to control and flexibly adapt our behavior as executive functions, including impulse control, action planning and emotion regulation. Getty Images / Dan Tuffs Price is on target as always, only for the occupation of the American embassy in Iran at the end of the 1970s she does not give the expected date. Later it turns out: The information in the book is wrong, Price is right. McGaugh and his colleagues were also able to determine that Price was by no means calculating calendars in his head, as is known, for example, from certain autistic people with island talents. Some of them can accurately compute data over a period of time up to years. Price, on the other hand, only remembers events since your autobiographical memory has been mysteriously accurate ever since. In further memory tests, however, Price puzzled the researchers: she also solved some tasks with flying colors, for example recognizing words. Without falling for a wrong word, Price easily recognized all 50 terms she had seen before. In the case of less structured tests such as the free recitation of learned word lists, on the other hand, it scored well below average. She says of herself that she regularly misplaces her keys and that she writes down a lot of things in everyday life so as not to forget them. Their intelligence is also only average. Noticeably difficult for Price with tests on the so-called executive functions, abstract, forward-looking thinking is not what she likes. Accordingly, she never had outstanding grades even in her school days, always had to study a lot and, according to her own statements, found it difficult to remember poems or historical data, McGaugh finally made the Price case public for the first time. In order to preserve their anonymity, he initially only referred to them with the abbreviation "AJ" in his study. A little later, however, Price went public himself, told her story in numerous television shows and at the end even wrote a book about her life with the extraordinary memory (see review in GuG 9/2009, p. 84). Thus, Jill Price is not only the first, but also by far the best-known person with hyperthymesis to date. Despite the large number of tests, the researchers do not know exactly why she can remember so well. In contrast to memory disorders, such an outstanding memory capacity had hardly been investigated until then and if so, then at most in connection with people who used special techniques to memorize a large number of unimportant things such as street maps or the number pi to several thousand decimal places. In addition, there were no suitable standardized testing procedures for people like Jill Price, which is why the researchers mainly examined them using methods that were actually intended for patients with memory disorders. Abnormal brain development? In the tests in which it was good, so-called ceiling effects often appeared: the tasks were simply too easy. Price solved them without reaching their limits, achieved a perfect result with some. McGaugh could only guess at the time that her unusual abilities were due to abnormal development of her brain. In mid-2012, researchers led by Brandon Ally from Vanderbilt University in Nashville approached this question. They wanted to find out what the memory of people 28 GuG 4_2013

4 how Jill makes Price so unique from a neuronal perspective. To do this, they examined a subject who had the same impressive skills as Price. The 20-year-old "HK" also has a superior autobiographical memory, but suffered from premature retinopathy as a toddler, which resulted in him becoming completely blind. Even so, he remembers every day of his life since he was 13 years old. Like Price, he does not consciously call up the memories, but they literally come over him. They are always lively and rich in sensory impressions. While Price watches the past "like a movie" in her mind's eye, the blind HK is mainly dominated by noises, smells and feelings. Like Price, HK is neither intelligent above average nor is he particularly good at memorizing things, only his autobiographical memory stands out. To clarify why this is so, Ally and his colleagues used structural magnetic resonance imaging (MRI) to target HD's brain. Compared to 30 other young men with no particular autobiographical memory, HD had less white and gray brain matter overall. The researchers attributed this to his early illness. On the other hand, its right amygdala, which took up 20 percent more volume than the control subjects, was significantly enlarged in relation to the entire brain. And this despite the fact that many other brain areas below the cerebral cortex, such as the basal ganglia, appeared to be smaller in relation to the entire organ of thought. Intensive connection promotes memory In addition, HD showed a much stronger network of the right amygdala with the hippocampus and other cortical and subcortical regions. The amygdala is part of the limbic system and is primarily responsible for processing information emotionally. It combines certain stimuli with emotions such as fear, and damage to it leads to the feeling of fear being noticeably disturbed. Because the amygdala in HD is so pronounced and particularly well networked, Ally and his colleagues suspect that it plays a crucial role in people with exceptional memory skills. Psychologists and “Jill Price's memory is particularly noteworthy when it comes to calendar dates. In this way, she can correctly enumerate all Easter days between 1980 and 2003 within ten minutes «a doubly good memory T he psychologist Hans mar kowitsch from the Hanse Wissenschaftskolleg in Delmenhorst, together with his colleague Angelica Staniloiu, examines the test person» FK «in a person with hyperthymesia. What is special about this person concerned: He also seems to have an excellent semantic memory at the same time. Professor Markowitsch, why do you suspect hyperthymesis in your FK test subject? There are many indications of this. For example, at the age of five he could already list the birthdays of many relatives, including the day of the week on which they fell. FK, too, often perceives its abilities as a burden and hides them from others. How does his excellent semantic memory show? For example, I once asked him what he thought of the numbers 49 and 32. "1749 was goethe's year of birth and he died in Weimar," he replied promptly. What is the difference between FK and other subjects with hyperthymesis? First of all, his general intelligence. FK is very talented. In addition, I consider it to be the "more normal" case: In early childhood we first acquire general knowledge of the world. The autobiographical memory develops only from the fourth year of life. It is therefore astonishing that the latter works so well for some even without a “semantic basis”. Hans Markowitsch is Professor of Physiological Psychology at Bielefeld University and is currently a Fellow at the Hanse Wissenschaftskolleg in Delmenhorst. Bielefeld University, press office 29

5 In contrast to the researchers working with Ally, McGaugh's team did not find any changes in the amygdala in the subjects concerned.Instead, they found differences to the control group in a total of nine other regions. Most of these areas were located in the temporal lobe of the cerebrum, such as the inferior and medial temporal gyrus or the temporal pole. Many of these regions had already proven to be important for autobiographical memory in previous studies. For the psychologist Hans Markowitsch from the University of Bielefeld it is not surprising that the temporal pole of all things plays an important role: »This is where the so-called uncinate fasciculus ends, a strand of nerve fibers that connects the frontal lobe with the temporal hyperthymesis Where I was Thinking safely The medial and inferior temporal gyrus as well as the inferior frontal cortex play a role in personal life events. The psychologist Hans Markowitsch sees the temporal pole at the tip of the temporal lobe as a key station of the autobiographical memory. inferior frontal cortex temporal pole inferior temporal gyrus medial temporal gyrus Brain researchers have long known the importance of feelings for our memory: We remember emotionally significant things much better than neutral stimuli. There is much to suggest that the amygdala "charges" the personal memories of HD with emotions and thus gives them great personal relevance. In addition, this system seems to be hyperactive with him, which is why he can process and store information more efficiently than other people. Meanwhile, it remained unclear whether the findings could be transferred to other people with hyperthymesis. In theory, some of the neuronal changes observed could simply result from the fact that HD is blind and that his brain has adapted to this circumstance over time. James McGaugh did not let go of the question of the cause of the extraordinary autobiographical memory in the past few years. In order to be able to carry out a study with more informative value, it was first necessary to identify more test persons with HSAM. McGaugh's team developed its own test procedure for this. The scientists were not short of potential test subjects after the publication of their first study in 2006, more than 100 people had contacted them who claimed to have a similarly perfect memory. The researchers first subjected their test participants to a multi-stage "quiz" on the brain and mind / Meganim [M] by telephone and filtered out a total of ten new HSAM test subjects. McGaugh invited her to his laboratory to check her memory and intelligence again in detail and to measure her brain in magnetic resonance tomography. For each study, McGaugh and his colleagues also put together a suitable control group of people with normal memory skills. The cognitive tests were largely similar to those that the researchers had taken Jill Price between 2000 and 2006. For example, the test subjects had to recognize faces, memorize sequences of numbers and recite them backwards, trace abstract images and repeat stories they had heard. Like Jill Price before, the new HSAM subjects only performed better than the control persons in a few tests, and most of the tasks they performed were absolutely average. However, there was a striking number of left-handers among those concerned. In addition, almost all HSAM subjects were prone to compulsive behavior. They hoarded certain things like CDs or toys from their childhood and organized them according to sometimes complicated rules. Some of them also said they were reluctant to touch doorknobs or use cutlery in restaurants for fear of germs. Switching point temporal pole 30 GuG 4_2013

6 lobes connects. This tract plays a key role in autobiographical memory. For example, there is a case study of a patient who suffered selective damage to the uncinate fasciculus in a racing bike accident. As a result, he could hardly remember any episodes from his life. His semantic memory, his world knowledge, on the other hand, was largely intact. ”Interestingly, in addition to a few other brain connections, this same uncinate fasciculus was particularly well developed in McGaugh's HSAM test subjects. Since the researcher compared the similarities of several subjects with control subjects in his study, his results seem to be more reliable than those of Ally. Memory researcher Hans Markowitsch, who is currently investigating a case of HSAM himself, is also impressed by the latest findings: “In studies with amnesia patients, the connection of the frontal areas of the brain with the temporal pole has proven to be particularly important for retrieval from autobiographical memory, even more important than that Amygdala and its connections to the hippocampus. «The search for the cause of the extraordinary autobiographical memory is not yet over. Mc-Gaugh also knows about the weaknesses of his study, which make further research necessary. In principle, it also remains unclear whether the observed brain changes actually represent the cause of the increased memory ability or whether it is not the other way around: Has the brain perhaps only changed due to the extraordinary memory performance and the regular use of this ability? To answer that, McGaugh and his colleagues want to concentrate more on examining children with HSAM in the future. Ÿ Daniela Zeibig is a freelance science journalist specializing in life sciences and medicine in Heidelberg. She can learn a lot of things by heart in a short time, but then forgets them just as quickly. »There were a striking number of left-handers among those concerned. In addition, almost all subjects were prone to compulsive behavior «Sources Ally, B. A.et al .: A Case of Hyperthymesia: Rethinking the Role of the Amygdala in Autobiographical Memory. In: Neurocase /, 2012 LePort, A. K. R. et al .: Behavioral and Neuroanatomical Investigation of Highly Superior Autobiographical Memory (HSAM). In: Neurobiology of Learning and Memory 98, S, 2012 Parker, E. S. et al .: A Case of Unusual Autobiographical Remembering. In: Neurocase 12, S, 2006 Hallucinations, fascination and horror New case stories by Oliver Sacks Translated from the English by Hainer Kober 352 pages. Hardcover 22.95 (D) / 23.60 (A) / sfr. 32.90 (RRP) Elena Seibert