State-dependent TMS reveals rotation-invariant shape representations in Lateral Occipital Cortex and Occipital Face Area

Abstract

Human extrastriate visual cortex contains functionally distinct regions where neuronal populations exhibit signals selective for visually presented objects. How such regions might play a causal role in underpinning our ability to recognize objects across different viewpoints remains uncertain. Here, we tested whether two extrastriate areas, the lateral occipital (LO) region and the occipital face area (OFA) contained neuronal populations that play a causal role in recognizing two dimensional shapes across different rotations. We used visual priming to modulate the activity of neuronal populations in these areas, and then applied TMS before presentation of a second rotated shape to which participants had to respond. Surprisingly, we found that TMS applied to both LO and OFA modulated rotationally invariant shape priming, but in a fashion that differed depending on the degree of rotation. Our results thus demonstrate that both the LO and OFA contain neuronal representations which play a causal role in rotation-invariant shape processing.