Representations and dynamics of representations of simple visual stimuli by ensembles of neurons in cat visual cortex studied with a microelectrode array

The features that constitute simple visual images are encoded by networks of interacting neurons at each level of the visual pathways. One such fundamental feature is line or bar orientation. It has long been appreciated that the neurons in the visual cortex appear to deconstruct images into sets of oriented lines. Thus, the neural representation of the orientation of moving bars by neural ensembles is a fundamental property of the vertebrate visual system. We have used high electrode count microelectrode arrays to study how the neurons of cat visual cortex encode simple moving stimuli, and what are the dynamics of this encoding process. Microelectrode arrays allow one to study these issues with both high spatial and temporal resolutions. We have used simple linear models to estimate stimulus orientation from ensemble firing patterns, and have found that groups of non-orientation sensitive neurons are as effective at encoding stimulus orientation as groups of orientation sensitive neurons. These findings have implications for both basic studies of neural encoding and for therapeutic applications such as human engineered artificial vision systems.