"Plis de passage": Examining the Role of Forgotten Sulcal Pleating Patterns as Predictors of Functional Boundaries in Visual Cortex

Abstract

Cortical folding has proven to be a very helpful indicator of the boundaries between different functional representations in sensory regions of the brain. For the most part, only major sulci and gyri have been analyzed in order to explore the predictive nature of cortical folding in these primary sensory cortices. Recently, some research groups have found that cortical folding is actually more coupled to functional representation boundaries in higher-level sensory regions than neuroscientists believed. A particular group is looking into a long-forgotten feature of sulci identified by Louis Pierre Gratiolet in 1854, called “plis de passage” – also referred to as pleats or annectant gyri – which may play a larger role in determining specific functional boundaries than we think. We analyzed these pleats in the paroccipital sulcus of the dorsal stream as well as the inferior frontal sulcus in ventrolateral prefrontal cortex. By defining the pleats across our subjects, determining whether they were consistent across our data pool, and analyzing functional properties represented by the distinct annectant gyri, we find that the anatomical structures prove to be reliable predictors of functional representation boundaries in the two distinct lobes. Thus, this study allows for a new insight into the functional predictivity of non-major anatomical structures within the brain, suggesting they are more significant than they might appear.