Spatiotemporal Patterns of Excitation and Inhibition Evoked by the Horizontal Network in Layer 2/3 of Ferret Visual Cortex

Abstract

The horizontal network in visual cortex layer 2/3 is implicated in numerous psychophysical and physiological properties. To investigate the spatial and temporal distribution of excitation and inhibition evoked by this network, we used voltage-sensitive dyes to image the responses to focal electrical stimulation in tangential slices of ferret visual cortex layer 2/3. The resulting optical patterns included a diffuse zone of activation near the stimulation site and numerous ovoid domains throughout the slice. In contrast to the fixed anatomy of the horizontal connections, substantial shifts in both space and time were evident in the distribution of population-based neuronal activity during stimulus trains. Both of these shifts relied on inhibitory synaptic potentials, suggesting that inhibition driven by horizontal connections sculpts the distribution of activity in this cortical network.

Inhibitory synchrony as a mechanism for attentional gain modulation

“…The network activation is controlled by neuromodulators, such as acetylcholine, or by activation of metabotropic glutamate receptors [78]. It depends also on the extent of the chemical and gap-junction couplings within local networks [1] and, possibly, on longer range connections between different local networks [83,84]. So a IV may reflect a combination of physiological parameters.…”

Negatively correlated firing: the functional meaning of lateral inhibition within cortical columns

“…Much of the existing work on inhibitory mechanisms in the context of cortical columns has focused on the role of lateral inhibition in sharpening distinctions between neurons with slightly different response properties [8,10]. However, the existence of local inhibitory circuits [12,13] and the fact that horizontal connections lead to inhibitory post-synaptic potentials (IPSPs) [6], suggest that inhibitory circuits are likely to operate within cortical columns, as well as across them.…”

High Precision and Fast Functional Mapping of Brain Circuitry through Laser Scanning Photostimulation and Fast Dye Imaging

“…The clustered activation domains seen in the tangential slices were similar to that found in ferret visual cortex, but at a much finer scale. This is perhaps due to the spatially restricted neuronal activation by photostimulation instead of electrical stimulation used in previous studies (Tucker & Katz, 2003). In addition, as LSPS activates many different sites with very short time intervals (e.g., see Figure 2A-B), our technique enables rapid mapping of neuronal circuitry by patterned photostimulation and VSD imaging of multiple V1 locations.…”