Intrinsic Curvature: A Marker of Millimeter-Scale Tangential Cortico-Cortical Connectivity?

Abstract

In this paper, we draw a link between cortical intrinsic curvature and the distributions of tangential connection lengths. We suggest that differential rates of surface expansion not only lead to intrinsic curvature of the cortical sheet, but also to differential inter-neuronal spacing. We propose that there follows a consequential change in the profile of neuronal connections: specifically an enhancement of the tendency towards proportionately more short connections. Thus, the degree of cortical intrinsic curvature may have implications for short-range connectivity.

Intrinsic gray-matter connectivity of the brain in adults with autism spectrum disorder

“…Atypical cortical morphology has previously been reported in ASD (33-36) and may be more "complex" than in controls (37,38). Our finding of reduced MSDs further supports the hypothesis that increased geometric complexity may underpin the development of shorter cortico-cortical fibers at the expense of longer connections (25,39). If so, a relative imbalance of short-to long-range cortical projections most likely also affects the way information is processed in the brain in ASD and may favor what some have suggested as a preference for local over global information (e.g., ref.…”

“…Such differential overgrowth in ASD will affect both overall size of the cortex and the way the brain is organized and "wired" (27). Our results, and the work of others, therefore suggest that measures of intrinsic geometry might also be used as an in vivo neuroimaging marker for nonuniform cortical expansion during development (25). In adults, it is often difficult to determine whether between-group differences result from (i) the primary pathology, (ii) a different neurodevelopmental trajectory, or (iii) general compensatory mechanisms unrelated to the primary pathology.…”

“…Differences in intrinsic geometry of the cortex have previously also been related to the density of neural units defining the surface architecture of individual cortical regions (25,30). Theoretically (Fig.…”

“…An uneven distribution of surface units (e.g., minicolumns) most likely arises as a consequence of nonuniform surface expansion during development, which is commensurate with a differential decrease in neuronal density and an increase in intercellular spacing (25,32). For example, it has previously been demonstrated that some regions expand earlier and to a higher extent than others in typical brain development, and such differential expansion will also affect the distances between regions on the cortical surface (e.g., ref.…”

“…Intrinsic connections have also been documented in other regions of the brain (e.g., visual, motor, and somatosensory cortices) (22) and may include components of the inhibitory cortical circuitry (e.g., wide-arbor basket cells) (23). Intrinsic connections are therefore an integral part of the horizontal (i.e., lateral) gray-matter architecture of the cortex, and their development has therefore been closely related to a variety of surface-based geometric features, including surface area (10), cortical separation distances (24), and Gaussian curvature (25). These measures are also known as intrinsic geometric measures as they are a property of the surface itself and are thus independent of how the cortex is embedded or "folded" in 3D space (24,26).…”