Structural connectivity of visuotopic intraparietal sulcus
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The intraparietal sulcus (IPS) contains topographically organized regions, similar to retinotopic maps in visual cortex. These regions, referred to as IPS1-4, show similar functional responses to the mapping tasks used to define them, yet differing responses to tests of other posterior parietal cortex (PPC) functions such as short-term memory, eye movements and object viewing, suggesting that they may have distinct patterns of structural connectivity to other parts of the brain. The present study combined functional magnetic resonance imaging (fMRI) mapping with diffusion tensor imaging (DTI) to describe white matter connections of visuotopic regions along the IPS, in 25 neurotypical young-adult participants. We found that posterior IPS more likely connects to retinotopically defined visual regions, and superior temporal gyrus, relative to anterior IPS. Anterior IPS regions 3 and 4 had higher connection probabilities to prefrontal regions, relative to posterior IPS. All four IPS regions showed inter-hemispheric connections to analogous regions in the opposite hemisphere, as well as consistent connections to the thalamus and regions of the striatum. Multivariate pattern classification at the group level reliably distinguished IPS regions from one another on the basis of connectivity patterns, especially for the most distal pairs of regions; occipital and prefrontal regions provided the most discriminating information. These findings advance our understanding of the structure of visuotopic IPS, with implications for functional differences between regions, and possible homologies between humans and macaques. Visuospatial functions dependent on the parietal cortex are frequently impaired in individuals with developmental disorders and those afflicted by cerebrovascular disease; the findings described here can be used as a basis for comparing connectivity differences in these populations.
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