Adapting to two orientations: disinhibition in a visual aftereffect.

The tilt aftereffect of adapating to two different orientations simultaneously is weaker than the aftereffect of adapting to the more effective of the two orientations alone. This finding is consistent with explanations of orientational after-effects in terms of lateral inhibition between cortical orientation detectors, but not with explanations in terms of neural "fatigue" from excitation.