Facilitatory and inhibitory after-effect of spatially localized grating adaptation

Aftereffects of spatially localized grating adaptation were measured for different locations of the adaptation grating relative to test grating. When the adaptation grating was located on or near the retinal area occupied by the test grating, contrast sensitivity was markedly reduced. When the adaptation grating was spatially separated from the test grating, contrast sensitivity was significantly increased. This aftereffect of spatially localized grating adaptation suggests that spatial-frequency-selective detectors are not spatially independent, but tonically inhibited by spatially contiguous mechanisms. Thus the adaptation of these mechanisms might cause an increase in contrast sensitivity of detectors subserving the test grating.