Luminance-contrast mechanisms in humans: visual evoked potentials and a nonlinear model.
Isolated-checks were luminance-modulated temporally to elicit VEPs. Bright or dark checks were used to drive ON or OFF pathways, and low or high-contrast conditions were used to emphasize activity from magnocellular or parvocellular pathways. Manipulation of stimulus parameters and frequency analysis of the VEP were performed to obtain spatial and contrast-response functions. A biophysical explanation is offered for why the opposite polarity stimuli drive selectively ON and OFF pathways in primary visual cortex, and a lumped biophysical model is proposed to quantify the data and characterize changes in the dynamics of the system with contrast given a limited number of parameters. Response functions were found to match the characteristics of the targeted pathways.
Zemon
Vance
V
Ferkauf Graduate School of Psychology, Yeshiva University, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, NY 10461, USA. vepman@aol.com
Gordon
James
J
D000328:Adult; D055592:Biophysical Phenomena; D001703:Biophysics; D015350:Contrast Sensitivity / Q000502:physiology; D005074:Evoked Potentials, Visual / Q000502:physiology*; D005260:Female; D006801:Humans; D008027:Light; D008875:Middle Aged; D008959:Models, Neurological; D009434:Neural Pathways / Q000502:physiology; D009474:Neurons / Q000502:physiology; D017711:Nonlinear Dynamics; D010775:Photic Stimulation / Q000379:methods; D012160:Retina / Q000502:physiology; D014793:Visual Cortex / Q000502:physiology; D014796:Visual Perception / Q000502:physiology*