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Case Reports
. 2009 Oct;15(5):361-72.
doi: 10.1080/13554790902776896. Epub 2009 Jul 6.

A slice of pi : an exploratory neuroimaging study of digit encoding and retrieval in a superior memorist

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Case Reports

A slice of pi : an exploratory neuroimaging study of digit encoding and retrieval in a superior memorist

Amir Raz et al. Neurocase. 2009 Oct.

Abstract

Subject PI demonstrated superior memory using a variant of a Method of Loci (MOL) technique to recite the first digits of the mathematical constant pi to more than 2(16) decimal places. We report preliminary behavioral, functional magnetic resonance imaging (fMRI), and brain volumetric data from PI. fMRI data collected while PI recited the first 540 digits of pi (i.e., during retrieval) revealed increased activity in medial frontal gyrus and dorsolateral prefrontal cortex. Encoding of a novel string of 100 random digits activated motor association areas, midline frontal regions, and visual association areas. Volumetric analyses indicated an increased volume of the right subgenual cingulate, a brain region implicated in emotion, mentalizing, and autonomic arousal. Wechsler Abbreviated Scale of Intelligence (WASI) testing indicated that PI is of average intelligence, and performance on mirror tracing, rotor pursuit, and the Silverman and Eals Location Memory Task revealed normal procedural and implicit memory. PI's performance on the Wechsler Memory Scale (WMS-III) revealed average general memory abilities (50th percentile), but superior working memory abilities (99th percentile). Surprisingly, PI's visual memory (WMS-III) for neutral faces and common events was remarkably poor (3rd percentile). PI's self-report indicates that imagining affective situations and high emotional content is critical for successful recall. We speculate that PI's reduced memory for neutral/non-emotional faces and common events, and the observed increase in volume of the right subgenual cingulate, may be related to extensive practice with memorizing highly emotional material.

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Figures

Figure 1
Figure 1
fMRI signal as a function of four experimental conditions at t>6. Brain slices are parallel to the anterior commissure–posterior commissure (AC-PC) line (Z = 0) and start at the top of the brain (top line left of the bold yellow line) in descending order (crossing over to the right hand side of the bold yellow line following Z = 18).
Figure 2
Figure 2
A direct statistical comparison of early (first 4 runs of Experiment 2) vs. late (remaining 4 runs of Experiment 2) learning at t>4.
Figure 3
Figure 3
A direct statistical comparison of π recitation (Experiment 1) vs. both early (first 4 runs of Experiment 2) and late (remaining 4 runs) recall of the 100 random digits at t > 6.

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