Question

7. Describe the role of lateral inhibition in sensation. How does this relate to the on center off surround in the retina?

Answer 1

Lateral inhibiton is a process whereby the application of stimulus to the center of the receptor feild excites a neuron, but a stimulus applied near the edge inhibits it., the primary afferent fibre whose receptive feild is closest to the point of stimulation will produce more action potential than those in the periphery, for example when an area of the skin is touched, the central excitatory region activates and the peripheral region is inhibited creating a contrast in sensation and allowing sensory precision.

Ganglion cells are the first neurons in the retina that responds with action potential, there are two primary types of ganglion cell receptor fields, each receptor field is arranged into a central disk, the center and a concentric ring the surround, each region responds oppositely to light, light in the center might increase the firing of a particular ganglion cell, where as light in the surround would decrease in the firing of that cell. Stimulation of ON- Center cells receptive field produces depolarization and increases the firing of the ganglion cell, but the stimulation of the surround produces hyperpolarization and decrease in the firing of the ganglion cell and stimulation of both center and surround produces a mild response. In contrast an OFF-Center cells is stimulated by the activation of the surround and inhibited by the stimulation of the center. The center- surround receptor field organization allows ganglion cells mainly to transmit information about contrast.