Representation of visual scenes by local neuronal populations in layer 2/3 of mouse visual cortex

Abstract

How are visual scenes encoded in local neural networks of visual cortex? In rodents, visual cortex lacks a columnar organization so that processing of diverse features from a spot in visual space could be performed locally by populations of neighboring neurons. To examine how complex visual scenes are represented by local microcircuits in mouse visual cortex we measured visually evoked responses of layer 2/3 neuronal populations using 3D two-photon calcium imaging. Both natural and artificial movie scenes (10 seconds duration) evoked distributed and sparsely organized responses in local populations of 70–150 neurons within the sampled volumes. About 50% of neurons showed calcium transients during visual scene presentation, of which about half displayed reliable temporal activation patterns. The majority of the reliably responding neurons were activated primarily by one of the four visual scenes applied. Consequently, single-neurons performed poorly in decoding, which visual scene had been presented. In contrast, high levels of decoding performance (>80%) were reached when considering population responses, requiring about 80 randomly picked cells or 20 reliable responders. Furthermore, reliable responding neurons tended to have neighbors sharing the same stimulus preference. Because of this local redundancy, it was beneficial for efficient scene decoding to read out activity from spatially distributed rather than locally clustered neurons. Our results suggest a population code in layer 2/3 of visual cortex, where the visual environment is dynamically represented in the activation of distinct functional sub-networks.

Adaptation and Neuronal Network in Visual Cortex

“…Visual cortex is a highly specialized functional area where the neurons coordinate locally to encode the visual scenes [89,90,91]. To reveal how this local circuitry of different neurons in visual cortex is set up and modulated in response to different visual stimuli is of prime importance to understand the mechanisms of information processing.…”

Method to quantify accuracy of position feedback signals of a three-dimensional two-photon laser-scanning microscope

“…Therefore, an accurate monitoring of the absolute position of the focal volume over time is the main requirement accomplishing a reliable reconstruction of the spatial information of targeted cells. So far, internal feedback signals of the microscope's positioning devices were routinely used to achieve this goal [2,4,10,17]. Using fluorescent beads embedded in agarose, the feasibility of reconstructing morphological information was shown [2].…”

“…Recently, the feasibility of quasi-simultaneous calcium imaging from hundreds of cells was demonstrated using three-dimensional random access scanning [14][15][16]. Alternatively, a simpler approach combines widely used classical galvanometric lateral scanning with a focusing piezo actuator, providing volume scans with an edge length of 100 -250 µm at 10 Hz by using a spiralshaped scan trajectory [2,17]. The disadvantage of losing morphological information of cellular targets by both continuous spiral scan trajectories and discontinuous random access scanning can be overcome by reconstructing the spatial information using a spatially highly resolved reference z-stack acquired directly before or after the fast functional measurements [2,[14][15][16][17].…”

“…Alternatively, a simpler approach combines widely used classical galvanometric lateral scanning with a focusing piezo actuator, providing volume scans with an edge length of 100 -250 µm at 10 Hz by using a spiralshaped scan trajectory [2,17]. The disadvantage of losing morphological information of cellular targets by both continuous spiral scan trajectories and discontinuous random access scanning can be overcome by reconstructing the spatial information using a spatially highly resolved reference z-stack acquired directly before or after the fast functional measurements [2,[14][15][16][17]. Therefore, an accurate monitoring of the absolute position of the focal volume over time is the main requirement accomplishing a reliable reconstruction of the spatial information of targeted cells.…”

Synergistic activity between primary visual neurons

“…Neurons principally coordinate in local sub-networks termed 'cell-assemblies' to represent distinct cognitive entities (Ko et al, 2013;Ko et al, 2011;Perin et al, 2011;Kampa et al, 2011;Hebb,1949;Buzsaki, 2010). Visual cortex is perhaps the most studied area of the brain; yet, how local circuits emerge to encode specific information in response to a visual input, is a question to be deeply explored -that is, how the intriguing interplay between the stimulus and a microcircuit is engineered and modulated?…”