Dr. Simons’ laboratory investigates neuronal integration within identified, small networks of cerebral cortical neurons. Studies focus on the component of the rodent somatosensory system that processes tactile information arising from the large facial vibrissae, or whiskers. Each whisker correlates one-to-one with an anatomically defined group of cortical neurons, called a barrel, that represents a morphological correlate of a functional cortical column. Barrels are local circuits that perform an initial transformation of incoming signals from the somatosensory thalamus. Computer-controlled whisker stimuli and single cell recording techniques are used to examine how information is integrated by cortical neurons, with a strong emphasis on processing in thalamocortical circuits and the effects of corticothalamic feedback. In collaboration with Dr. George Carvell, recordings also are obtained from animals trained to perform tactile discriminations using their whiskers.

Neurophysiological findings are incorporated into computer models of sensory cortex that simulate known synaptic connections among cortical neurons and the thalamic cells that are presynaptic to them. The model networks are activated by pre-recorded spike trains from thalamocortical relay cells, and responses of the model neurons are compared quantitatively with those obtained in real barrels. In colloboration with Dr. Bard Ermentrout, simulations are used to understand how the dynamical properties of the local circuit account for the neurons’ receptive fields.

Other studies examine the physiological and behavioral effects of abnormal tactile experiences early in life that are produced by trimming the whiskers during critical developmental stages. Trainees in Dr. Simons’ laboratory have the opportunity to combine neurophysiological and modeling studies of cortical neuronal networks. Experimental techniques include single- and multi-electrode recordings, animal behavioral training, computer-based data analyses, and mathematical simulation.