It has a corresponding property in intermediate level vision, that of contour integration. Even in V1, neurons’ responses show selectivity for the properties of extended contours with complex geometries. Neurons’ responses are greatly facilitated by collinear interactions, where a line placed outside the RF, which by itself will elicit no response, can facilitate a neuron’s response several-fold

selleck inhibitor when placed in conjunction with a collinear line segment within the RF (Figure 2; Kapadia et al., 1995, 2000). Blocking the continuity between line segments by a perpendicular line will eliminate the facilitation, but moving the perpendicular line segment into a different depth plane than the two collinear line segments, which restores their perceived continuity, recovers the facilitatory interaction of the collinear lines on neurons’ responses (Bakin et al., 2000). The properties of natural scene contours, the perceptual strategies by which we link contour elements, and the contextual interactions seen in V1 RFs are represented by the intrinsic circuitry of V1. An important feature of V1 connections is the plexus of long-range horizontal connections, which enable neurons to integrate inputs from an area of cortex representing an area of visual

field that is much larger than their classical RFs. The extent and orientation dependence of long-range horizontal connections match the properties of salient contours and the geometry of natural scene contours (Figure 3; Gilbert and Wiesel, 1989; Stettler et al., 2002; Li and Gilbert, ADP ribosylation factor click here 2002). By the same token, the visual system contains an internal representation of these principles, as observed in psychophysical studies of contour saliency (Field et al., 1993; Li and Gilbert,

2002), in facilitatory contextual influences on neuronal responses in V1 (Kapadia et al., 2000; Li et al., 2006; McManus et al., 2011) and in the long-range horizontal connections (Gilbert and Wiesel, 1989; Stettler et al., 2002). Together, these findings support the idea that the association field is represented in V1, and that the circuitry underlying lateral interactions in V1 mediates the linkage of scene elements into global contours. The horizontal connections play a role in experience-dependent plasticity. Such plasticity is invoked in the normal process of perceptual learning and in recovery of function following CNS damage, such as that associated with stroke or neurodegenerative disease. Even in adult animals, the adult visual cortex is capable of undergoing experience-dependent change. A valuable model for studying the mechanism of cortical plasticity at the levels of RF properties, changes in circuitry and molecular mechanism involve the reorganization of cortical topography following retinal lesions (Calford et al., 2000; Chino et al., 1992; Eysel et al., 1999; Giannikopoulos and Eysel, 2006; Gilbert et al.