Borders of Multiple Visual Areas in Humans Revealed by Functional Magnetic Resonance Imaging

TLDR

The study used phase‑encoded retinal stimulation to acquire fMRI data, reconstructed cortical surfaces to compute local visual‑field sign, and automatically delineated visual‑area borders where adjacent fields have opposite signs. Precise, noninvasive borders of V1–V4 were mapped, revealing that human visual areas have a larger central‑gaze emphasis than monkeys and that retinotopic maps extend anteriorly overlapping word‑processing regions.

Abstract

The borders of human visual areas V1, V2, VP, V3, and V4 were precisely and noninvasively determined. Functional magnetic resonance images were recorded during phase-encoded retinal stimulation. This volume data set was then sampled with a cortical surface reconstruction, making it possible to calculate the local visual field sign (mirror image versus non-mirror image representation). This method automatically and objectively outlines area borders because adjacent areas often have the opposite field sign. Cortical magnification factor curves for striate and extrastriate cortical areas were determined, which showed that human visual areas have a greater emphasis on the center-of-gaze than their counterparts in monkeys. Retinotopically organized visual areas in humans extend anteriorly to overlap several areas previously shown to be activated by written words.