Precise visuotopic organization of the blind spot representation in 2 primate V 1 3 4 João

25 The optic disk is a region of the retina consisting mainly of ganglion cell axons and blood vessels, 26 which generates a visual scotoma known as the blind spot (BS). Information present in the 27 surroundings of the BS can be used to complete the missing information. However, the neuronal 28 mechanisms underlying these perceptual phenomena are poorly understood. We investigate the 29 topography of the blind spot representation (BSR) in cortical area V1 of the capuchin monkey, using 30 single and multiple electrodes. Receptive fields (RFs) of neurons inside the BSR were investigated 31 using two distinct automatic bias-free mapping methods. The first method (local mapping) consisted 32 in randomly flashing small white squares. For the second mapping method (global mapping) we 33 used a single long bar that moved in 1 of 8 directions. The latter stimulus was capable of eliciting 34 neuronal activity inside the BSR, possibly due to long-range surround activity taking place outside 35 the borders of the BSR. Importantly, we found that the neuronal activity inside the BSR is organized 36 topographically in a manner similar to that found in other portions of V1. On average, the RFs inside 37 the BS were larger than those outside. However, no differences in orientation or direction tuning 38 were found between the two regions. We propose that area V1 exhibits a continuous functional 39 topographic map, which is not interrupted in the BSR, as expected by the distribution of 40 photoreceptors in the retina. Thus, V1 topography is better described as “visuotopic” rather than as a 41 discontinuous “retinotopic” map. 42 43