How does a brain that never forgets work?

Is it possible to recall almost every event in our lives in extraordinary detail, and what happens in the brain of people who can do this? A new study set out to answer these questions by investigating individuals with highly superior autobiographical memory, a rare condition that allows people to recall personal experiences with unusual precision and detail.

To explore this, researchers compared three individuals with this exceptional memory ability to 16 participants without it. While listening to cues such as “the first time you went to a concert” or “the last time you cooked something,” all participants were asked to retrieve personal memories, first identifying the memory and then reliving it in as much detail as possible, while their brain activity was recorded using electroencephalography (EEG).

The results revealed subtle but important differences in how the brain retrieves memories. During the initial phase of accessing memories, individuals with superior memory showed a stronger increase in brain activity in the theta frequency band (associated with cognitive control and memory retrieval), particularly when recalling older events. This pattern suggests that these individuals may organise and reconstruct complex memories more efficiently, as if navigating the past with greater precision.

During the subsequent phase of re-experiencing the details of those memories, another intriguing pattern emerged. While typical participants showed an initial increase in alpha activity (often associated with the suppression of irrelevant stimuli), individuals with superior memory did not display this initial peak. This may indicate that they can access vivid mental images more directly, with less need to inhibit irrelevant sensory information, making the process more fluid, as if the past were always ready to be relived.

Overall, the study suggests that extraordinary memory is not only about storing more information, but also about accessing it more efficiently and flexibly. However, the study was based on a very small number of individuals with this rare ability, and future research with larger samples will be essential to confirm these mechanisms and deepen our understanding of how the human brain can achieve such remarkable memory performance. To learn more, check the article Modulation of midfrontal theta and posterior alpha during the construction and elaboration of autobiographical memories in individuals with highly superior autobiographical memory, published in the journal Neuropsychologia, within the framework of the research project 75/20 – Psychophysiology of highly superior autobiographical memory: Shedding light on the mind of people who never forget, led by Valerio Santangelo and supported by the Bial Foundation.

ABSTRACT

Individuals with highly superior autobiographical memory (HSAM) represent a rare population with the exceptional ability to recall autobiographical information with remarkable precision and detail. While research has begun to explore the neural mechanisms underlying this extraordinary memory performance, the role of brain oscillations has not yet been investigated in HSAM individuals. Here, we studied three individuals with HSAM and compared their results with 16 controls. We asked all participants to retrieve newer and older autobiographical memories (AMs) while their electroencephalogram (EEG) was being recorded. Participants were asked to press a button to indicate access and construction of their AM and to continue elaborating it. We focused on midfrontal theta oscillations during the construction phase of AM retrieval and posterior alpha oscillations during the elaboration phase. Compared to the controls, the HSAM participants exhibited greater theta during the retrieval of older as compared to newer AMs, and no increase of the initial posterior alpha during the elaboration phase power. These findings may reflect more efficient neural processes in HSAM individuals. Specifically, the selective midfrontal theta enhancement during retrieval of remote memories suggests a flexible engagement of control and inhibitory mechanisms, supporting complex memory construction. The lack of initial posterior alpha increase could indicate reduced cortical suppression and, speculatively, more vivid visual imagery during elaboration. These findings shed light on the unique neural dynamics underlying HSAM individuals and offer new insights into how their autobiographical memory is supported by highly efficient neuro-cognitive processes.