Population Response to Contextual Influences in the Primary Visual Cortex

Abstract

Collinear proximal flankers can facilitate the detection of a low-contrast target or generate false-alarm target detection in the absence of a target. Although these effects are known to involve subthreshold neuronal interactions beyond the classical receptive field, the underlying neuronal mechanisms are not fully understood. Here, we used voltage-sensitive dye imaging that emphasizes subthreshold population activity, at high spatial and temporal resolution and imaged the visual cortex of fixating monkeys while they were presented with a low-contrast Gabor target, embedded within collinear or orthogonal flankers. We found that neuronal activity at the target site in area primary visual cortex increased and response latency decreased due to spatial spread of activation from the flankers' site. This increased activity was smaller than expected by a linear summation. The presentation of flankers alone induced strong spatial filling-in at the target site. Importantly, the increased neuronal activity at the target site was synchronized over time, both locally and with neuronal population at the flanker's site. This onset synchronization was higher for collinear than for orthogonal flankers. We further show that synchrony is a superior code over amplitude, for discriminating collinear from orthogonal pattern. These results suggest that population synchrony can serve as a code to discriminate contextual effects.

Population Response to Natural Images in the Primary Visual Cortex Encodes Local Stimulus Attributes and Perceptual Processing

“…3, bottom; Meirovithz et al, 2010). However, this can be linked to the fact that in our set of natural images we found a significant negative spatial correlation between the local luminance and contrast.…”

“…with q ϭ 3 and L 50 ϭ 0.1 (Sit et al, 2009;Meirovithz et al, 2010), to account for the nonlinearity response of V1 neurons to contrast and luminance (Fig. 3D).…”

“…We used voltage-sensitive dye imaging (VSDI) (Grinvald et al, 1999;Slovin et al, 2002;Ayzenshtat et al, 2010;Meirovithz et al, 2010) to record neural population activity from cell assemblies distributed throughout a continuous cortical surface corresponding to a few square degrees of the visual field. To investigate the stimulus-response relationship, we com-puted a 2D analytical transformation of the visual stimulus into cortical coordinates and then studied the spatial correlation between features of the transformed stimulus and the evoked neural activity.…”

Cortico-cortical Communication Dynamics

“…Part of the explanation might be that the dye signal in vivo reflects synaptic activity at the mesoscopic scale, whereas the action potential recordings capture the activity of single neurons (Lippert et al, 2007;Eriksson et al, 2008). Nevertheless, in several studies one can follow how net increases in the synaptic activity propagate over the cortical areas when the cortex is perturbed by a sensory transient (Senseman, 1996;Prechtl et al, 1997;Senseman and Robbins, 2002;Slovin et al, 2002;Grinvald and Hildseheim, 2004;Roland et al, 2006;Ferezou et al, 2007;Lippert et al, 2007;Xu et al, 2007;Ahmed et al, 2008;Han et al, 2008;Takagaki et al, 2008;Yoshida et al, 2008;Harvey et al, 2009;Ayzenshtat et al, 2010;Meirovithz et al, 2010;Ng et al, 2010;Polack and Contreras, 2012;Harvey and Roland, 2013). This synaptic dynamics may show some order in the feed-forward propagation of net-excitation for example between V1 and V2 in monkeys, rats and turtles, between the barrel field and the motor cortex in the mouse, and between visual areas 17, 18 and 19, 21 in the ferret.…”

“…The whole primary auditory cortex was engaged in 26-40 ms after stimulus start in guinea pigs (Horikawa et al, 1998;Kubota et al, 2012). The whole craniotomy exposed part of the primary visual cortex in ferrets, cats, and monkeys became engaged 48-70 ms after stimulus start, even with small stimuli (Slovin et al, 2002;Jancke et al, 2004;Eriksson and Roland, 2006;Roland et al, 2006;Sharon et al, 2007;Eriksson et al, 2008;Harvey et al, 2009;Ayzenshtat et al, 2010;Meirovithz et al, 2010;Roland, 2010;Chavane et al, 2011;Reynaud et al, 2012;Harvey and Roland, 2013). In mice and rats it took some 70-110 ms for the dynamics to engage the whole primary visual cortex Han et al, 2008;Gao et al, 2012;but Lim et al, 2012: 46 ms;Polack and Contreras, 2012).…”