Yang Z, Heeger DJ, Seidemann E. Rapid and precise retinotopic mapping of visual cortex obtained by voltage sensitive dye imaging in the behaving monkey. Journal of Neurophysiology, 98:1002-1014, 2007.
Abstract: Retinotopy is a fundamental organizing principle of the visual cortex. Over the years, a variety of techniques have been used to examine it. None of these techniques, however, provides a way to characterize retinotopy rapidly, at the sub-millimeter range, in alert, behaving subjects. Voltage sensitive dye imaging (VSDI) can be used to monitor neuronal population activity at high spatial and temporal resolutions. Here we present a VSDI protocol for rapid and precise retinotopic mapping in the behaving monkey. Two monkeys performed a fixation task while thin visual stimuli swept periodically at a high speed in one of two possible directions through a small region of visual space. Because visual space is represented systematically across the cortical surface, each moving stimulus produced a traveling wave of activity in the cortex that could be precisely measured with VSDI. The time at which the peak of the traveling wave reached each location in the cortex linked this location with its retinotopic representation. We obtained detailed retinotopic maps from a region of ~1 cm2 over the dorsal portion of areas V1 and V2. Retinotopy obtained during less than 4 minutes of imaging had a spatial precision of 0.11-0.19 mm, was consistent across experiments, and reliably predicted the locations of the response to small localized stimuli. The ability to rapidly obtain precise retinotopic maps in behaving monkeys opens the door for detailed analysis of the relationship between spatiotemporal dynamics of population responses in the visual cortex and perceptually guided behavior.