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STATIONARY PATTERN ADAPTATION AND THE EARLY COMPONENTS IN HUMAN VISUAL EVOKED POTENTIALS
Citation:
Hudnell, H., W. Boyes, AND D. Otto. STATIONARY PATTERN ADAPTATION AND THE EARLY COMPONENTS IN HUMAN VISUAL EVOKED POTENTIALS. U.S. Environmental Protection Agency, Washington, D.C., EPA/600/J-90/129 (NTIS PB91109686).
Description:
Pattern-onset visual evoked potentials were elicited from humans by sinusoidal gratings of 0.5., 1, 2 and 4 cpd (cycles/degree) following adaptation to a blank field or one of the gratings. The wave forms recorded after blank field adaptation showed an early positive component, PO, which decreased in amplitude with spatial frequency, hereas the immediately succeeding negative component, N1, increased in amplitude with spatial frequency. O and NI components of comparable size were recorded at 1 cpd. tationary pattern adaptation to a grating of the same spatial frequency as the test grating significantly reduced Nl amplitude at 4,2 and 1 cpd. he N1 component elicited at 4 cpd was attenuated in log-linear fashion as the spatial fluency of the adaptation grating increased. O, on the other hand, was unaffected by stationary pattern adaptation at all combinations of test and adapting spatial frequencies, although PO amplitude is known to be attenuated by adaptation to a drifting grating. ince N1, but not PO, was significantly attenuated following adaptation and testing at 1 cpd, it was concluded that the neurons generating these components are functionally distinct. he use or a common adaptation grating discounted the possibility that N1, but not PO was affected due to a difference in the rates of retinal image modulation caused by eye movements made while viewing adaptation gratings of different spatial frequencies. he neurons generating N1 were adapted at a lower rate of retinal image modulation than that apparently required for adaptation of the neurons generating PO, which suggests a difference between these neurons in the rate of stimulus modulation necessary for activation.