2017年第二届曲阜视觉科学会议知识库

PURPOSE: To investigate inter-areal and inter-laminar interactions during contour detection and their context dependency.
METHODS: Two macaque monkeys were trained to detect visual contours formed by collinear bars when a cluttered background was present or absent. We simultaneously recorded neuronal responses at retinotopically matched locations in V1 and V2 while the monkeys performed the detection task. The recordings were done with a pair of laminar probes with 24 recordings sites spaced 100 µm apart and perpendicular to the cortical surface. We quantified the contour signals in different layers of V1 and V2, dissected the inter-areal directional interactions using Granger causality, and examined the temporal dynamics of laminar interactions in the presence and absence of interfering context.
RESULTS: When the cluttered background was present, the responses of most V1 and V2 recording sites were significantly enhanced in delayed response components by the global contours centered on their receptive fields. These contour-signaling sites were mainly concentrated in V1 supragranular and upper infragranular layers, and in V2 supragranular and granular layers. These cortical layers were also the main layers showing contour-related interactions during 100-300 ms, when the contour signals rapidly increased. In contrast, when the background was absent, neuronal responses in V1 supragranular and granular layers were suppressed; responses in V2 were enhanced, but the latencies of contour-related signals were markedly shortened. Inter-areal interactions related to contour integration also shifted to early response components before 100 ms.
CONCLUSIONS: Contour grouping engages inter-areal interplay among specific cortical layers; inter-areal exchange of information takes place within a limited time window; inter-areal and inter-laminar interactions are dependent on stimulus complexity.