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Authors & Affiliations
Hamish Meffin, Zuitian Tao, Jordan Sibberas, Anthony Burkitt, Michael Ibbotson
Abstract
Motion is encoded by the visual system using multiple cues. In primary visual cortex (V1), one cue is the tracking of object edges in a direction perpendicular to their orientation. Another cue, called motion streak, relates to tracking fast objects that create a smeared perception of motion along their trajectory. Intriguingly, dual tuning, to both cues in the same neuron, occurs in mutually perpendicular directions. We aimed to determine if dual tuning is predicted by a neuron’s spatio-temporal receptive field (STRF). Drifting white noise (DWN) patterns were presented at range of speeds (0:1:64 °/s) and directions (0:22.5:337.5°) while recording from cat V1. Cells were classified as orientation- (OS) or direction-selective (DS) using drifting gratings. 81 neurons tuned to both cues were identified. At low DWN speeds, DS cells (n=32) were selective to a direction perpendicular to their preferred orientation (Fig. a), while OS cells (n=49) were not direction selective. This is consistent with sensitivity to edge-like features present in drifting gratings. However, at high speeds, both types of cell preferred the direction parallel to their orientation (Fig. b). Next, an STRF model was inferred from electrophysiological data to predict responses to DWN for each cell. The tuning of model responses matched the measured tuning for both low and high speeds in terms of firing rate and direction-selectivity (e.g., DS cell in Figs. c & d, correlation = 0.96; population range: 0.81-0.96), indicating that dual encoding of these motion cues is explained by integration within the STRF.