Evidence for disparity detecting neurones in the human visual system.

1. It is known that adaptation to a grating pattern causes a rise in the contrast threshold for test gratings of similar spatial frequency and orientation.2. We find this after-effect also to be disparity-specific. Adaptation to a grating at zero horizontal disparity (at the same distance as the fixation point) causes a greater elevation of threshold for patterns at the same disparity than for those at nearby disparities, closer or more distant than the fixation point.3. Adaptation to a grating at some disparity other than zero causes a disparity-specific elevation of threshold centred on the adapting disparity.4. This finding also applies if the observer adapts to a grating but single bright bars are used as the test stimuli.5. The disparity-specific ;tuning curves' revealed by these techniques are quite broad, having a half-width at half-amplitude of several min of disparity.6. Adaptation to a grating at one disparity causes an apparent change in the distance of test gratings at nearby disparities.7. We compare these psychophysical experiments with the properties of disparity-selective binocular neurones in the visual cortex of cats and monkeys.