Binocular neurons
[1][2] Binocular neurons receive inputs from both the right and left eyes and integrate the signals together to create a perception of depth.
[1] Using a stereoscope, he showed that horizontal disparity is used by the brain to calculate the relative depths of different objects in 3-dimensional space in reference to a fixed point.
[3] These classes were called simple and complex cells, which differ in how their receptive fields respond to light and dark stimuli.
Béla Julesz in 1971 used random dot stereograms to find that monocular depth cues, such as shading, are not required for stereoscopic vision.
[1] Disparity selective cells were first recorded in the striate cortex (V1) of the cat by Peter Orlebar Bishop and John Douglas Pettigrew in the late 1960s,[1] however this discovery was unexpected and was not published until 1986.
[5] Additionally, population responses of binocular neurons have been found in human ventral and dorsal pathways using fMRI.
[7] Binocular neurons, in the sense of being activated by stimuli in either eye, are first found in the visual cortex in layer 4.
[7][9] In the prestriate cortex (V2) and ventral extrastriate area (V4), binocular neurons respond most readily to a centre-surround stimulus.
The cells in this pathway are sensitive to the relative depth between different objects or features close to one another in the physical world which is called fine stereopsis.
[1][13][14][15] Energy models of binocular neurons involve the combination of monocular receptive fields that are either shifted in position or phase.
The relative contributions of phase and position shifts in simple and complex cells combine together in order to create depth perception of an object in 3-dimensional space.
[13][14] The position-shift model suggests that the receptive fields of left and right simple cells are identical in shape but are shifted horizontally relative to each other.
[1] According to the phase-difference model the excitatory and inhibitory sub-regions of the left and right receptive fields of simple cells are shifted in phase such that their boundaries overlap.
As one example, the model uses independent Fourier phases for some types of stimuli, and finds the preferred disparity of the complex cells equal to the left-right receptive field shift.
[1] Disparity attraction and repulsion is believed to be directly related to the physiological properties of binocular neurons in the visual cortex.
[1] Use of the stereo model has allowed for interpretation of the source of differing peak locations found in disparity tuning curves of some cells in visual cortex.
