Specificity of surround interaction for global motion directionality in awake monkey V1

Abstract

Neurons of the primary visual cortex (V1) process visual information presented within the classical receptive field (cRF), and this local information is thought to be integrated with that outside the cRF to recover global visual features in later stages. However, it has been known that even in the V1, neuronal activity is modulated by stimuli outside the cRF. In line with this, it was reported that V1 neurons are modulated by temporal interval of spatiotemporal stimulus sequence extending beyond the cRF (Kim et al., 2012), suggesting that V1 neurons participate in processing stimulus motion extending beyond the cRF – global motion. In the current study, we tested the hypothesis that V1 neurons have directional preference for global motion extending beyond the cRF, and that this is based on fine-tuned surround interaction. Specifically, we measured global directional preference with a sequence of two focal stationary Gabor stimuli

the preceding one (S1) presented outside the cRF and the following one (S2) presented inside the cRF with a stimulus onset asynchrony (SOA) of 50 or 100ms. The S1 stimulus appeared at either flanking sides of the cRF before the S2, thus making two directions of stimulus sequence. And this was compared with local directional preference that we measured with a Gabor stimulus confined within the cRF that drifted along two directions orthogonal to preferred orientation. Although the S1 alone did not evoke spiking responses, the response to the S2 was significantly modulated by the S1, consistent with the previous study (Kim et al., 2012). The magnitude of modulation was asymmetrical between the two sequence directions, indicating that the cells showed a direction preference for apparent motion consisting of S1 and S2 that extended beyond the cRF. There was a significant positive relationship between global and local directional preferences, suggesting that V1 neurons tend to prefer the global motion direction that matched with their local directional preference. This positive correlation was significant for SOA of 50ms, but not for 100ms. These results suggest that V1 neurons participate in processing global motion based on surround interaction that is fine tuned for spatial and temporal relations between center and surround stimuli.