Binocular disparity discrimination in human cerebralcortex: functional anatomy by positron emission tomography.

Abstract

Neurobiological studies in higher primates indicate that the processing of stereoscopic information takes place at early levels in the visual cortex. To map the anatomical structures in the human brain participating in pure stereopsis based upon binocular disparity, we measured with positron emission tomography the changes in regional cerebral blood flow as an indicator of metabolic activity in 10 healthy young men during visual discrimination of binocular disparity. The data demonstrate that the discrimination of pure stereoptic disparity information takes place in the polar striate cortex and the neighboring peristriate cortices, as well as in the parietal lobe, the prefrontal cortex, and the cerebellum. The discrimination of stereoscopic depth is dependent on a network composed of multiple functional fields localized in occipital-and parietal-lobe visual areas as well as in the dorsolateral and mesial prefrontal cortex. The findings support the importance of coactivated occipitoparietal visual areas in the processing and analysis of binocular depth information in humans.Psychophysical studies in humans (1-3) have indicated that the various submodalities of visual perception may be processed and analyzed in the visual system by different "functional processing streams," which are, as in other higher primates (4-6), related to anatomically separable subdivisions ofthe visual pathways. Among others, stereopsis based on binocular disparity is a fundamental visual submodality (7)(8)(9)(10). Single-cell studies in the macaque monkey (11)(12)(13)(14) have revealed that many neurons in the striate cortex and in the peristriate cortices respond to binocular disparity stimulation. Nevertheless, the localization and extent of areas subserving stereoscopic vision at the levels of neuronal populations in primates, including humans, have not yet been revealed.Recently, positron emission tomography (PET) has been instrumental in demonstrating that, indeed, different modality-specific visual cortical areas in the human brain are involved in the early analysis of color, form, and motion information (15)(16)(17)(18)(19). By using PET with an experimental paradigm related to the detection of horizontal disparity, here we show those areas in the human brain which are specifically engaged in pure binocular disparity detection. METHODS Subjects. Ten healthy male volunteers [mean age; 32.6 + 11.9 (SD) years] participated in the present study. The subjects were fully informed about the objectives, details, and risks of the experiment, and they have given a written consent, in agreement with the Helsinki Declaration and the OPRR Reports (20). They denied any neurological, psychological, and ophthalmologic history. Eight of them were emmetropes, and two had corrected-to-zero vision. The study was approved by the Ethical, Radiation Safety, and Magnetic Resonance Committees ofthe Karolinska Hospital.Stimulus Design. The stimulus paradigms were designed with the following requirements in mind: Ci) in each task identical stimulus ...

Neural Correlates of Disparity-Defined Shape Discrimination in the Human Brain

“…In contrast, previous studies implicated areas V3A (Backus et al 2001;Gulyas and Roland 1994;Mendola et al 1999;Tsao et al 2003) and V3B/KO (Brouwer et al 2005;Tyler et al 2006;Van Oostende et al 1997;Zeki et al 2003) in the analysis of disparity-defined surfaces and boundaries. Further, caudal intaparietal (CIP) regions were previously implicated in processing 3D object orientation and surface slant (James et al 2002;Naganuma et al 2005;Sakata et al 2005;Taira et al 2000) rather than being involved in form discrimination (Shikata et al 2001).…”

“…We examined the average fMRI response evoked by stimuli with different levels of disparity-defined shape coherence in early visual areas (V1, V2, V3, V3A, V3B/KO, VP/V3, V4), higher ventral areas (LOC: LO, pFs), and dorsal visual areas (hMTϩ/V5: MT, MST) previously implicated in the processing of disparity information in the human brain (i.e., disparitydefined planes: Backus et al 2001;Gulyas and Roland 1994;Neri et al 2004;Rutschmann and Greenlee 2004;Tyler et al 2006;shape contours: Gilaie-Dotan et al 2002;Kourtzi et al 2002Kourtzi et al , 2003Mendola et al 1999;or gradients: (Brouwer et al 2005;Welchman et al 2005). Figure 3, B-D shows the effect of increasing disparitydefined shape coherence on the fMRI response across cortical areas (V1, V2, ventral, dorsal areas).…”

Parietal and hippocampal contribution to topokinetic and topographic memory

“…Recent work by Gru« sser and others in the monkey (Gulya¨s & Roland 1994;Gru« sser et al 1990aGru« sser et al ,b, 1991 The subject is passively rotated in darkness, only viewing the head-¢xed target, and is asked to remember the location of the earth-¢xed target. The only information available to the subject about the rotation is derived from the horizontal semicircular canal.…”

M Pathway and Areas 44 and 45 Are Involved in Stereoscopic Recognition Based on Binocular Disparity.

“…Stereoscopic vision has been studied intensively at both the theoretical and computational levels [1][2][3]. Since stereoscopic recognition is known to exhibit a diverse and moderately complicated phenomena, which are well suited for study at the neurophysiological level, human brain mapping involved in stereoscopic recognition have been of growing interest [4][5][6][7][8].Lesion analyses in humans [9][10][11] indicate that the parietal cortex plays a major role with a suggestion of right-hemisphere dominance for stereoscopic recognition. For example, patients with anterior temporallobe lesions demonstrate impaired global stereopsis but intact local stereoacuity [9].…”

“…Stereoscopic vision has been studied intensively at both the theoretical and computational levels [1][2][3]. Since stereoscopic recognition is known to exhibit a diverse and moderately complicated phenomena, which are well suited for study at the neurophysiological level, human brain mapping involved in stereoscopic recognition have been of growing interest [4][5][6][7][8].…”