Lateral Connectivity and Contextual Interactions in Macaque Primary Visual Cortex

Abstract

Two components of cortical circuits could mediate contour integration in primary visual cortex (V1): intrinsic horizontal connections and feedback from higher cortical areas. To distinguish between these, we combined functional mapping with a new technique for labeling axons, a recombinant adenovirus bearing the gene for green fluorescent protein (GFP), to determine the extent, density, and orientation specificity of V1 intrinsic connections and V2 to V1 feedback. Both connections cover portions of V1 representing regions of visual space up to eight times larger than receptive fields as classically defined, though the intrinsic connections are an order of magnitude denser than the feedback. Whereas the intrinsic connections link similarly oriented domains in V1, V2 to V1 feedback displays no such specificity. These findings suggest that V1 intrinsic horizontal connections provide a more likely substrate for contour integration.

Selective interhemispheric circuits account for a cardinal bias in spontaneous activity within early visual areas

“…However, anatomical studies indicate that feedback connections exhibit a lesser degree of orientation selectivity (Stettler et al, 2002) than intracortical axons and deactivation studies did not reveal pronounced specificity.…”

“…patchy long-range lateral axons interconnecting neurons responding to the same feature space, e.g. orientation preference (Gilbert and Wiesel, 1989;Malach et al, 1993;Bosking et al, 1997;Schmidt et al, 1997b;Stettler et al, 2002). Accordingly, ongoing population activity in cortex would be biased toward states that reflect the spatial configuration of that patterned connections (Kenet et al, 2003;Muir et al, 2011).…”

“…There is manifold evidence that neurons in the visual cortex responding to contours of the same orientation are preferentially linked by long-range patchy connections (Gilbert and Wiesel, 1989;Malach et al, 1993;Bosking et al, 1997;Schmidt et al, 1997a;Stettler et al, 2002). A close relationship between the anatomical configuration of that patch system as determined by tracer injections, and the structure of maps acquired through visual stimulation has been suggested (Muir et al, 2011).…”

On the functions, mechanisms, and malfunctions of intracortical contextual modulation

“…Such facilitation is greatest at target contrasts just above the cell's firing threshold (Polat and Norcia, 1996;Polat et al 1998), and includes cases where the flankers are placed at separations of 12 degrees or more (Mizobe et al, 2001), which is beyond the furthest extent of the cell's distal RF (Angelucci et al, 2002). This facilitation is mediated both by long-range intra-regional connections (Stettler et al, 2002) and by feedback from higher regions (Angelucci et al, 2002).…”

Bayesian Networks for Modeling Cortical Integration

“…Typically, a hypercolumn occupies a cortical area of V1 [17,24,25]. Such contextual influences, considered to be mediated by modulatory influences of the extraclassical receptive field, are presumed to arise from the horizontal inputs from neighboring hypercolumns and/or from feedback from extrastriate areas [7,10,36,37,46]. …”