Physiological Correlate of the Pulfrich Effect
Citation Info
Thom Carney, Michael A. Paradiso, and Ralph D. Freeman (1989)
A physiological correlate of the Pulfrich effect in cortical neurons of the cat.
Vision Res 29: 155-165.
Abstract
When a swinging pendulum is viewed with a light-attenuating filter
before one eye, the pendulum bob is perceived to move in an elliptical path
in depth. It is believed that the filter causes this illusion, the Pulfrich
effect, by delaying processing of the image in the filtered eye relative to
that of the unfiltered eye. We sought a physiological correlate of this
effect by studying binocular integration in cortical neurons of cats while
they viewed moving stimuli. Special attention was focused on single unit
disparity tuning because it is widely believed that depth perception is
related to the responses of disparity selective neurons in visual cortex.
We found that placing a filter before one of the cat's eyes produced a
temporal delay in the cortical response. The temporal delay was always
associated with a shift in the neuron's spatial disparity tuning. The
observed temporal delays and disparity shifts are comparable with the
magnitude of the Pulfrich effect in humans.