Cognitive insights from tertiary sulci in prefrontal cortex

Abstract

The lateral prefrontal cortex (LPFC) is disproportionately expanded in humans compared to non-human primates, although the relationship between LPFC brain structures and uniquely human cognitive skills is largely unknown. Here, we test the relationship between variability in LPFC tertiary sulcal morphology and reasoning scores in a cohort of children and adolescents. Using a data-driven approach in independent discovery and replication samples, we show that the depth of specific LPFC tertiary sulci is associated with individual differences in reasoning scores beyond age. To expedite discoveries in future neuroanatomical-behavioral studies, we share tertiary sulcal definitions with the field. These findings support a classic but largely untested theory linking the protracted development of tertiary sulci to late-developing cognitive processes.

Sulcal depth in prefrontal cortex: A novel predictor of working memory performance

“…Thus, a shallow, short sulcus would compensate for a particularly long and deep nearby sulcus, rendering the overall degree of cortical folding within a given region approximately equal (Armstrong et al, 1995;Connolly, 1950;Zilles et al, 2013). Given this hypothesis, we propose that a relatively deeper tertiary sulcus, which may have stronger short-range white matter connections as proposed previously (Voorhies et al, 2021), may be close to sulci that are relatively shallower, thereby preserving the degree of local cortical folding. This proposal builds on a recent modification of the compensation theory of cortical folding that proposes to also incorporate local morphological features (Natu et al, 2020).…”

“…This normalized sulcal depth is reported in standard Freesurfer units. To assess the relation between sulcal anatomy and verbal WM performance, we applied a data-driven approach (Voorhies et al, 2021). Below, we discuss the results of our approach in which we found that a) VLPFC sulci are shallower and more variable than mid-DLPFC sulci, b) sulcal depth is related to verbal WM manipulation, c) nine left-hemisphere LPFC sulci, but no right-hemisphere LPFC sulci defined in the present study predict manipulation scores, and d) these brain-behavior relations are not generalizable, as the cortical thickness of these nine sulci is not related to verbal WM performance.…”

“…Yet, additional studies define sulci in this cortical expanse as secondary (Tamraz and Comair, 2006). As in our previous studies (Miller et al, 2021a,b;Voorhies et al, 2021), we consider the imfs-h and imfs-v as primary sulci in the present study, but it is possible that future studies will establish them as secondary sulci. Of course, the definition of primary, secondary, and tertiary sulci remains contentious, which is why we refer to LPFC tertiary sulci explored in the present study as "putative."…”

“…2 for demographic information). 48 of these participants were also included in Voorhies et al (2021). Participants ranged in age from 6 to 18 (M = 12.12, SD = 3.39; Females: M = 11.82, SD = 3.23; Males: M = 12.36, SD = 3.50).…”

“…Third, due to the protracted development of both tertiary sulci and higher order cognitive skills associated with LPFC, Sanides (1962Sanides ( , 1964 proposed a classic hypothesis that tertiary sulci likely serve as anatomical and functional landmarks that are behaviorally relevant in association cortices such as LPFC. In recent years, there has been mounting evidence in support of Sanides' hypothesis in ventral temporal cortex across the lifespan (VTC; Weiner, 2019), as well as in medial PFC (Lopez-Persem et al, 2019) and in LPFC in both adults and children (Voorhies et al, 2021). Directly relevant for the present study, the latter findings-supported by the notion that depth is a characteristic feature of tertiary sulci, which are much more shallow than primary and secondary sulci (Armstrong et al, 1995;Weiner, 2019)-showed that the depth of a subset of right-lateralized LPFC tertiary sulci correlated with performance on a visuospatial reasoning task.…”