Neuropsychological investigation of "The amazing memory man"

Objective: Mnemonists, memory champions, and persons with highly superior autobiographical memory (HSAM) are apparently rare breeds, with no more than a few dozen cases of each described in the neuroscientific literature. This report describes a newly discovered HSAM case who has extraordinary memory for a wider range of material than has heretofore been described. Method: Subject MM was interviewed about his personal life and administered standard clinical tests of cognition and personality, as well as experimental tasks assessing personal and generic episodic and semantic memory. Finally, he was studied with high resolution structural MRI of the medial temporal lobes, as well as brain connectivity analysis using resting-state functional MRI. Results: MM's ability to recall general factual information, historical facts and dates, sports statistics, and popular culture, as well as personal life experiences, is exceptional, even though he performs in only the average range on tests of intellect and new learning ability. Unlike most mnemonists, he denies using any specific mnemonic strategy and, unlike many other HSAM cases, is unable to recall highly specific details of days in his adult life. Structural brain imaging in MM reveals atypical anatomy in his left temporal lobe, and functional neuroimaging suggests greater than usual connectivity of the left hippocampus with premotor, prefrontal and retrosplenial cingulate cortex. Conclusions: These observations are discussed in the context of previous studies of mnemonists and HSAM cases, some of which implicate hyperconnectivity among components of an expanded memory network in extraordinary memory retrieval.