Does Retinotopy Influence Cortical Folding in Primate Visual Cortex?
NMR Martinos Center, Massachusetts General Hospital, Harvard Medical School, Charlestown, Massachusetts 02129, USA.The Journal of Neuroscience : The Official Journal of the Society for Neuroscience (Impact Factor: 6.34). 10/2009; 29(36):11149-52. DOI: 10.1523/JNEUROSCI.1835-09.2009
In humans and other Old World primates, much of visual cortex comprises a set of retinotopic maps, embedded in a cortical sheet with well known, identifiable folding patterns. However, the relationship between these two prominent cortical variables has not been comprehensively studied. Here, we quantitatively tested this relationship using functional and structural magnetic resonance imaging in monkeys and humans. We found that the vertical meridian of the visual field tends to be represented on gyri (convex folds), whereas the horizontal meridian is preferentially represented in sulci (concave folds), throughout visual cortex in both primate species. This relationship suggests that the retinotopic maps may constrain the pattern of cortical folding during development.
Full-textDOI: · Available from: Roger B Tootell, Feb 25, 2014
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- "More generally, Van Essen proposed that the overall pattern of cortical folding is determined by the pattern of intracortical axonal connections, which engage in a global tug-of-war that minimizes total axonal tension. Consistent with this axonal tension hypothesis, several studies have shown that axonal connections in highly folded cortices tend to be relatively short and straight, connecting adjacent gyral walls more frequently than expected by chance (Van Essen 1997, Hilgetag & Barbas 2006, Rajimehr & Tootell 2009). Unfortunately, the connectional data cannot discriminate cause from effect. "
ABSTRACT: Why the cerebral cortex folds in some mammals but not in others has long fascinated and mystified neurobiologists. Over the past century-especially the past decade-researchers have used theory and experiment to support different folding mechanisms such as tissue buckling from mechanical stress, axon tethering, localized proliferation, and external constraints. In this review, we synthesize these mechanisms into a unifying framework and introduce a hitherto unappreciated mechanism, the radial intercalation of new neurons at the top of the cortical plate, as a likely proximate force for tangential expansion that then leads to cortical folding. The interplay between radial intercalation and various biasing factors, such as local variations in proliferation rate and connectivity, can explain the formation of both random and stereotypically positioned folds. Expected final online publication date for the Annual Review of Neuroscience Volume 38 is July 08, 2015. Please see http://www.annualreviews.org/catalog/pubdates.aspx for revised estimates.Annual Review of Neuroscience 04/2015; 38(1). DOI:10.1146/annurev-neuro-071714-034128 · 19.32 Impact Factor
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- "While the pattern of sulci and gyri may be specified innately, it may also be that in visual cortex, cortical folding is at least partially dependent on the connections between neighboring functional units such as visual field maps (Allman and Kaas 1974). Van Essen proposed that gyri may form as a result of minimizing the distance between strongly interconnected regions of spatially adjacent functional areas on the brain (Van Essen 1997; Rajimehr and Tootell 2009). For example, the boundary between V1 and V2v is generally on the crown of the lingual gyrus. "
ABSTRACT: A strong relationship between cortical folding and the location of primary sensory areas in the human brain is well established. However, it is unknown if coupling between functional responses and gross anatomy is found at higher stages of sensory processing. We examined the relationship between cortical folding and the location of the retinotopic maps hV4 and VO1, which are intermediate stages in the human ventral visual processing stream. Our data show a consistent arrangement of the eccentricity maps within hV4 and VO1 with respect to anatomy, with the consequence that the hV4/VO1 boundary is found consistently in the posterior transverse collateral sulcus (ptCoS) despite individual variability in map size and cortical folding. Understanding this relationship allowed us to predict the location of visual areas hV4 and VO1 in a separate set of individuals, using only their anatomies, with >85% accuracy. These findings have important implications for understanding the relation between cortical folding and functional maps as well as for defining visual areas from anatomical landmarks alone.Cerebral Cortex 04/2013; 24(9). DOI:10.1093/cercor/bht092 · 8.67 Impact Factor
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- "This does not imply that cortical magnification has to be strictly locally isotropic, but curvature affects the overall layout. Recently, the influence of cortical folding in primate did also take into account the concave folds . We apply tensor analysis to investigate how these symmetries, i.e., isotropy and meridional symmetry, relate to the gross folding pattern, in particular the concave fold of the CS that creates additional cortical space for the representation of the visual field close to the horizon. "
ABSTRACT: Abstract The cortical magnification matrix M is introduced founded on a notion similar to that of the scalar cortical magnification factor M. Unlike M, this matrix is suitable to describe anisotropy in cortical magnification, which is of particular interest in the highly gyrified human cerebral cortex. The advantage of our tensor method over other surface-based 3D methods to explore cortical morphometry is that M expresses cortical quantities in the corresponding sensory space. It allows us to investigate the spatial relation between sensory function and anatomical structure. To this end, we consider the calcarine sulcus (CS) as an anatomical landmark for the primary visual cortex (V1). We found that a stereotypically formed 3D model of V1 compared to a flat model explains an excess of cortical tissue for the representation of visual information coming from the horizon of the visual field. This suggests that the intrinsic geometry of this sulcus is adapted to encephalize a particular function along the horizon. Since visual functions are assumed to be M-scaled, cortical folding can serve as an anatomical basis for increased functionality on the horizon similar to a retinal specialization known as visual streak, which is found in animals with lower encephalization. Thus, the gain of surface area by cortical folding links anatomical structure to cortical function in a previously unrecognized way, which may guide sulci development.Journal of Mathematical Neuroscience 12/2012; 2(1):14. DOI:10.1186/2190-8567-2-14