Stereopsis-processing regions in the human parieto-occipital cortex

Abstract

We performed fMRI on the human parieto-occipital cortex in order to identify the neural processing regions of stereopsis. Visual stimulation for stereopsis was performed with a random-dot stereogram displayed in the image guides of a new binocular visual stimulation device that we developed. Interestingly, regions from the dorsal portion of the occipital lobe to the superior parietal lobule were activated by binocular disparity, while the inferior parietal lobule was not activated. Moreover, these regions were shown as dominant in the right hemisphere. Functional brain mapping revealed that the processing regions of stereopsis were dorsally located in parieto-occipital cortex, and that the superior parietal lobule is an important region for neural processing of human stereopsis.

Neural Mechanisms for Binocular Depth, Rivalry and Multistability

“…However, later studies which performed analysis over a larger number of visual areas found that the activation levels are highest in dorsal occipito-parietal areas, such as V3A, V7, V4d-topo and caudal intraparietal sulcus relative to others [3,[5][6][7][8]. Moreover, considering all these studies together, the most consistent sites of activation for depth across many previous fMRI studies were V3A, V7, V4d-topo, or other lateral occipital areas, such as MT+, lateral occipital complex, and kinetic occipital area [2,3,5,6,8,10,13], as well as intraparietal sulcus [2,3,[6][7][8][9][10][11][12] and superior parietal lobe [2,6,7,8,[10][11][12]. In addition, ventral temporal cortical areas, including the fusiform gyrus, have also been noted to be depth selective [2,16,17].…”

“…In these studies, stimulus blocks showing images with depth were contrasted with blocks with no depth [2,3,6,7,[9][10][11][12]17], or correlated disparity versus anticorrelated disparity images [13]. Other depth studies used methods more similar to those used for binocular rivalry, such as multivoxel pattern analysis [8], event-related adaptation [15], event-related designs in which brain activation was correlated to changes in perceived depth [5,16], or adaptation in a block design to assess population responsiveness to different types of depth stimuli [14].…”

“…Other depth studies used methods more similar to those used for binocular rivalry, such as multivoxel pattern analysis [8], event-related adaptation [15], event-related designs in which brain activation was correlated to changes in perceived depth [5,16], or adaptation in a block design to assess population responsiveness to different types of depth stimuli [14]. These differences in methodology also mean that subjects performed a task in rivalry or multistabiity studies using event-related designs [5,19,20,22,[28][29][30]32,33,36], or block designs [1,2,26,31,34,35], but subjects did not perform tasks in depth studies [3,6,[9][10][11][12][13]17], although there are a few exceptions to this generalization for depth [2,4,5,7,17]. Also, a few rivalry or multistability studies did not use a task [21,37,61], and some rivalry studies used fixation tasks unrelated to the perception of rivalry [23,28].…”

“…Again, part of these differences can be attributed to the fact that there were more depth studies that had an interest in reporting activation in occipital areas, but even taking this into consideration, the overall pattern shows that occipital activation was relatively more prominent in depth studies. In general, few previous depth studies performed a whole-brain analysis [2,3,5,[7][8][9][10][11][12]16], and of these few, only three reported frontal activation [2,9,10]. It was not clear whether this was simply an absence of reporting, or due to the fact that there was no frontal activation because a task was not being performed in most of these studies.…”

“…It was not clear whether this was simply an absence of reporting, or due to the fact that there was no frontal activation because a task was not being performed in most of these studies. The areas reported in these few whole-brain studies were the usual set of prominent occipito-parietal areas we might expect, such as V2, V3, V3A, V4d-topo, V7, intraparietal sulcus and parietal lobe [2,3,5,[7][8][9][10][11][12]16]. A useful area for future study would be more matched comparisons between depth and rivalry, in which dynamic changes in depth (and a task to report depth percepts) could be used to make a direct comparison to rivalry studies.…”