Sulcal variability in anterior lateral prefrontal cortex contributes to variability in reasoning performance among young adults

Abstract

Identifying structure-function correspondences is a major goal among biologists, cognitive neuroscientists, and brain mappers. Recent studies have identified relationships between performance on cognitive tasks and the presence or absence of small, shallow indentations, or sulci, of the human brain. Building on the previous finding that the presence of one such sulcus in the left anterior lateral prefrontal cortex (aLPFC) was related to reasoning task performance in children and adolescents, we tested whether this relationship extended to a different sample, age group, and reasoning task. As predicted, the presence of this aLPFC sulcus-the ventral para-intermediate frontal sulcus-was also associated with higher reasoning scores in young adults (ages 22-36). These findings have not only direct developmental, but also evolutionary relevance-as recent work shows that the pimfs-v is exceedingly rare in chimpanzees. Thus, the pimfs-v is a novel developmental, cognitive, and evolutionarily relevant feature that should be considered in future studies examining how the complex relationships among multiscale anatomical and functional features of the brain give rise to abstract thought.

Keywords: Comparative biology; Cortical folding; MRI; Neuroanatomy; Prefrontal cortex; Reasoning.

Figure 1.. The para-intermediate frontal sulcus (pimfs) is variable across individuals and hemispheres.

A. Inflated left hemispheres (sulci: dark gray; gyri: light gray; cortical surfaces are not to scale) depicting four types of the pimfs: (i) both pimfs v/d present, (ii) neither present, (iii) pimfs-d present, (iv) pimfs-v present. Prominent sulci surrounding the pimfs are shown: horizontal (imfs-h) and ventral (imfs-v) intermediate frontal sulci and inferior frontal sulcus (ifs; see legend). B. Stacked bar plot depicting pimfs incidence in left (lh) and right (rh) hemispheres (N = 72; see rightward legend). C. Maximum probability maps (MPMs) for pimfs-d (top) and pimfs-v (bottom) on the inflated fsaverage cortical surface (left surfaces: rh; right surfaces: lh). For visual clarity, the MPMs were thresholded at 10% overlap across participants (the warmer the color, the higher the overlap). (*** p < 0.001).

Figure 2.. Relational reasoning is related to left pimfs-v presence.

A. Raincloud plots (Allen et al. 2021) depicting Penn Progressive Matrices task score as a function of left pimfs-v presence in younger adults (present, N = 57; absent, N = 14). Large dots and error bars represent mean ± std reasoning score; violin plots represent kernel density estimate. Small dots indicate individual participants. B. Histogram visualizing results of the iterative resampling of left pimfs-v presence in A 1,000 times. Distribution of the effect size (Cohen’s d) is shown, along with the median (black line) and 95% CI (dotted lines). Red line corresponds to zero, highlighting that left pimfs-v absence was never associated with higher reasoning scores than left pimfs-v presence. (** p < .01).