Effective connectivity reveals strategy differences in an expert calculator.

Ludovico Minati,Natasha Sigala

doi:10.1371/journal.pone.0073746

Abstract

Mathematical reasoning is a core component of cognition and the study of experts defines the upper limits of human cognitive abilities, which is why we are fascinated by peak performers, such as chess masters and mental calculators. Here, we investigated the neural bases of calendrical skills, i.e. the ability to rapidly identify the weekday of a particular date, in a gifted mental calculator who does not fall in the autistic spectrum, using functional MRI. Graph-based mapping of effective connectivity, but not univariate analysis, revealed distinct anatomical location of “cortical hubs” supporting the processing of well-practiced close dates and less-practiced remote dates: the former engaged predominantly occipital and medial temporal areas, whereas the latter were associated mainly with prefrontal, orbitofrontal and anterior cingulate connectivity. These results point to the effect of extensive practice on the development of expertise and long term working memory, and demonstrate the role of frontal networks in supporting performance on less practiced calculations, which incur additional processing demands. Through the example of calendrical skills, our results demonstrate that the ability to perform complex calculations is initially supported by extensive attentional and strategic resources, which, as expertise develops, are gradually replaced by access to long term working memory for familiar material.

Highlights

The study of calendrical skills, i.e. the ability to rapidly name the weekday corresponding to a particular date, is usually confined to savants, who are individuals gifted with specific skills but often affected by deficits in social and other intellectual domains [1]
Response accuracy was highest for close dates (97%), lower for intermediate dates (82%) and lowest for remote dates (77%); notably, the accuracy in the control task (96%) did not reach ceiling level, possibly due to response mapping errors
Close and remote dates in the past and future differed substantially in level of practice (YV’s own report), which reflected in perceived difficulty, response accuracy and reaction times

Summary

Introduction

The study of calendrical skills, i.e. the ability to rapidly name the weekday corresponding to a particular date, is usually confined to savants, who are individuals gifted with specific skills but often affected by deficits in social and other intellectual domains [1]. The ability to mentally perform calendrical calculation seems to be an acquired trait, developed as a consequence of obsessive preoccupation with calendars through extraction of rules and regularities, e.g. 28-year and 400-year cyclical repetitions [2], [3], [4]. Calendrical skills are occasionally found even in cognitively and behaviourally normal individuals: while this is a rare occurrence, plausibly because of lack of interest and motivation, it demonstrates that such skills can be acquired [5]; notable examples include Professor A. Aitken [6], [7] and Professor Conway [3], both distinguished academic mathematicians

Methods

Results

Conclusion