Slide 24

Artificial Scotomas Alter the Receptive Field Structure of Some Neurons

Example of the effect of the sequence of stimulation illustrated in Figure 22. The top trace is the average membrane potential in the cortical cell. Presentation of an artificial scotoma results in a depolarization of the cell, although this response adapts over a period of 30 seconds. Following this, presentation of a high contrast whole field sinewave grating results in a robust response that shows adaptation. Return to the artificial scotoma results in a marked hyperpolarization of the neuron. NOTE that the presentation of the identical visual stimulus, the artificial scotoma, results in either a strong depolarization of the cell, if it is presented after a gray screen, or a hyperpolarization of the neuron, if it is presented after strong stimulation of the neuron.

Mapping of the receptive field revealed a marked contraction following the whole field high contrast receptive field stimulation (bottom 3 maps) and an expansion following either a gray screen or an artificial scotoma.