Human visual cortical areas

Anders Dale and I have developed several high resolution methods for mapping visual areas in humans in collaboration with Roger Tootell and the Massachusetts General Hospital functional NMR group in Charlestown (see Dale and Sereno, 1993; Sereno et al., 1995; Tootell et al., 1995).

In the course of this work, we developed a method for reconstructing the complete cortical surface of individual subjects from MRI images. Functional MRI data is then painted onto these surfaces, which can be gently 'inflated' to reveal portions of the cortex normally hidden in sulci. Here are some images from that work. This is Anders' brain.

A method for finding the borders

Analysis of functional MRI data by visual field sign (mirror-image vs. non-mirror-image visual field representation). Mirror-image areas (yellow-e.g., V1), and non-mirror-image areas (blue-e.g., V2) are shown in a medial view on the folded (A) and unfolded cortical surface (B) and in a ventral view, folded (C) and unfolded (D). Ventral V1, V2, VP, and V4v, comprising four re-representations of the upper visual field, are visible below the incision in the fundus of the calcarine sulcus while lower visual field V1 and V2 are visible above it.

Comparisons with other primates

Schematic summary of retinotopic visual areas in the owl monkey, the macaque monkey, and the human at the same scale in (A) and approximately normalized by the area of V1 in (B) (human V1 is twice the area of macaque V1, with larger ocular dominance columns and cytochrome oxidase blobs, but a similar number of cells). Visual areas in humans show a close resemblance to visual areas originally defined in monkeys. The anterior border of visual cortex in humans was estimated using the superior temporal sulcus and intraparietal sulcus as landmarks. In (C), the mapping functions (scale on left axis) and magnification factor functions (scale on right axis) are shown for the upper field representations of human V1, V2, VP and V4. The V1 mapping functions for owl monkeys (OM*, dotted) and macaque monkeys (MM*, dashed) shown at the left were scaled up to match the overall size of human V1. An increased emphasis on the center of gaze in human V1 is evident.

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