Different cortical connectivity patterns have been used to explain the development and function of the primary visual cortex across varying time scales and stimulus protocols. Modellers looking at the long-term development of the cortex have generally assumed Mexican-Hat lateral interactions. Similarly, psychophysical studies of surround modulation have primarily focused on long-range inhibition, leading to the term "surround suppression". Yet the actual anatomical substrate for long-range interaction appears to mediated by excitatory connections . Electrophysiologists have long known that V1 neuron responses differ markedly depending on contrast and distance of the stimuli  and some modeling work has suggested differences in the excitatory and inhibitory populations as the cause. Here we propose a model that explains how each of these sources of evidence is compatible with a single underlying circuit, which effectively reduces to Mexican-Hat connectivity for high-contrast inputs. The model is based on two anatomically and functionally distinct inhibitory populations: the wide-arbor perisomatically targeting and Parvalbumin-immunoreactive (Pv-ir) basket cells with weakly tuned, low-latency suppression [2,3], and the smaller, high-latency and strongly tuned somatostatin-expressing (Som-ir) inhibitory interneurons, which could provide long-range orientation-specific inhibition through polysynaptic circuits . This anatomically grounded V1 circuit and the resulting model is the first to demonstrate how the observed connectivity patterns can emerge, and analyzes their role in mediating surround facilitation and suppression. Through manipulation of individual neural populations, as in recent experiments by Nienborg et al. , we predict that the PV-ir and Som-ir populations are intricately involved in mediating the contrast response and surround modulatory effects exhibited by neurons in V1 across species.
|Publication status||Published - 2013|
|Event||Society for Neuroscience Annual Meeting 2013 - San Diego, United States|
Duration: 9 Nov 2013 → 13 Nov 2013
|Conference||Society for Neuroscience Annual Meeting 2013|
|Period||9/11/13 → 13/11/13|