Evidence for disparity detecting neurones in the human visual system

Abstract

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.

Stereospatial masking and aftereffect with normal and transformed random-dot patterns

“…Stereoscopic masking was highly specific in that adaptation had no influence on detection, except around 6 minarc crossed disparity, when the successively presented binocular stimuli differed in disparity by 2 minarc or more. This range is far smaller than the 12-minarc (Blakemore & Hague, 1972) and the 30-45-minarc (Felton, Richards, & Smith, 1972) values that have been obtained with binocularly viewed gratings.…”

“…Within this logic, the masking functions obtained in Experiments I and II indicate that the disparity-selectivity of detectors mediating stereoscopic depth perception with random-dot patterns extends over a range of less than ±2 minarc. This value is appreciably less than the disparity ranges of ±12 minarc (Blakemore & Hague, 1972) and ±30 to 45 minarc (Felton, Richards, & Smith, 1972) obtained in masking experiments in which binocularly viewed gratings in the same or in different visual planes were used as adaptation and target stimuli. It was suggested earlier that the latter estimates bear on the tuning of neural mechanisms mediating coarse stereopsis, while the use of random-dot patterns to provide depth information in the present experiments has yielded data specific to fine stereopsis.…”

“…The rationale underlying studies of spatial masking is that exposure to one pattern can impair detection of another pattern only to the extent that the two stimuli are processed in the visual system by the same neural units (see Blakemore & Campbell, 1969;Blakemore & Hague, 1972). Within this logic, the masking functions obtained in Experiments I and II indicate that the disparity-selectivity of detectors mediating stereoscopic depth perception with random-dot patterns extends over a range of less than ±2 minarc.…”

Binocular masking level differences in sinusoidal grating detection

“…RECENT experiments of BLAKEMORE and HAGUE (1972) indicate that the detectability of sinusoidal gratings seen binocularly against a uniform background depends on the interocular phase of the gratings. Gratings that are identical in the visual fields of the two eyes are more readily detected than gratings presented 180" out-of-phase, that is with the maxima of the grating in one field in a location corresponding to the minima of the grating in the other.…”

The dynamics of the visual system in combining conflicting KDE and binocular stereopsis cues

“…Prolonged observation of an object at one depth can change the apparent distance of the object (Blakemore & Julesz, 1971) and elevate its detection threshold (Blakemore & Hague, 1972;Felton, Richards, & Smith, 1972;Stevenson, Cormack, Schor, & Tyler, 1992). These phenomena lead to an expectation that a self-adaptation of the stereopsis mechanism should also occur for our conflicting-cue stimulus, as well as for the self-adaptation of the KDE mechanism.…”