Dr. Carson Chow
MATHEMATICAL CELL MODELLING SECTION
NIDDK, National Institutes of Health
Friday 11 June 2010
4 th Floor Seminar Room, Alexandra House
A cortical circuit model of working memory, visual perception and neural disorders
Abstract: Neurons in the cortex exhibit a wide range of dynamics in response to external stimuli that are correlated with behavior. In the simplest example, a neuron's firing rate is tuned to a specific stimulus. These stimulus tuned neurons can then fire persistently after the stimulus is removed if the animal is required to perform a memory task and shut off after the task is completed. When presented with multiple stimuli, several responses can occur. In some cases, the activity of the neurons will sum sublinearly or normalize in response to multiple stimuli within their receptive field. For ambiguous stimuli as in binocular rivalry, neural activity may oscillate and the oscillations are correlated with the perception. The period of the oscillations can also change depending on the context with an infinite period corresponding to complete disambiguation. Here, I will show that a simple canonical cortical circuit consisting of recurrent excitation and lateral inhibition with parameters in the physiological regime is sufficient to account for all of these dynamics. In addition, certain neural disorders such as autism may arise from perturbations to the canonical cortical circuit.
Several autism genes are related to an increase of synaptic excitation over inhibition. This change in synaptic balance leads to an excess of persistent activity that can account for deficits in visually guided saccade tasks seen in autistic patients. The canonical cortical circuit may serve as a bridge linking genotype to phenotype for neural disorders.