初级视皮层神经元响应反应与撤反应的朝向选择性

Orientation Selectivity of Onset and Offset Responses of Neurons in Primary Visual Cortex

朝向选择性是初级视皮层(17区或V1)神经元的基本性质,在图形感知中起着关键作用.同时这些神经元对于持续时间大于100 ms的视觉刺激具有清晰的响应反应(Onset responses)和撤反应(Offset responses).以往的研究只关注响应反应的朝向选择性,而忽视了对撤反应的朝向选择性研究.我们比较了响应与撤反应的朝向调谐性质,大多数细胞的撤反应与响应反应基本上具有相似的最优朝向,而撤反应的朝向调谐宽度有窄于响应反应的趋势,撤反应的最优延迟普遍滞后于响应反应的最优延迟.撤反应的朝向选择性略强于响应反应和具有显著长的反应延迟提示,皮层内的反馈输入可能在形成撤反应的朝向选择性中起着作用.本研究揭示了撤反应的朝向选择性在刺激朝向的连续表征和主体在形状知觉的后期对朝向的精细区分中起着作用.

Orientation selectivity is an important property of neurons in the primary visual cortex （area 17 or V 1） and plays significant roles in the perception for object shape. V1 neurons also show clear responses to the Onset and Offset of a stimulus that lasts more than 100 ms, called as Onset and Offset responses, respectively. Previous studies have focused on Onset responses, while Offset responses were neglected. We investigated orientation selectivity of both Onset and Offset responses by presenting the stimuli of oriented gratings for 200 ms and showed that the preferred orientations of Offset responses are similar to that of Onset responses for most neurons. Moreover, the orientation tuning widths of Offset responses of most ceils tended to be narrower than that of Onset responses, and the response latencies of Offset oriented responses significantly were longer than those of Onset responses. The strong orientation selectivity and long response latency of Offset responses relative to those of Onset responses suggest that the intracortical feedback inputs may contribute to the enhancement in orientation tuning of Offset responses. The orientation selectivity of Offset responses provides a neural substrate for the more precise discrimination and consecutive representation of the orientated borders of a shape over time.