Artikel,

Binocular depth perception and the cerebral cortex

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Nature Reviews Neuroscience, 8 (5): 379--391 (2007)
DOI: 10.1038/nrn2131

Zusammenfassung

Humans and some other animals use their two eyes in coordination to support binocular depth perception. The left and right eyes obtain images of the visual scene from slightly different viewpoints, leading to small differences between the left and right images called binocular disparities.Measurement of the tuning functions of neurons in the visual cortex for disparity gives important information about how the visual stimulus influences the firing of neurons but does little to reveal the roles of different neurons in binocular depth perception.Known features of binocular stereoscopic depth perception can be used to set up tests of the role of individual neurons and individual cortical areas.One early hypothesis was that the dorsal visual cortical pathways are pre-eminently responsible for binocular depth perception. Other views have assigned different roles to the dorsal and ventral streams.Neurons outside the primary visual cortex (V1) respond consistently to relative disparity. Neurons in both dorsal and ventral extrastriate visual areas respond to relative disparity.It is proposed that dorsal areas are predominantly involved in processing extended visual surfaces and resolving depth structure during self-movement, whereas ventral visual areas process relative disparity to support the analysis of the three-dimensional shape of objects.Binocular anticorrelation can be used to map the role of different sites in the visual cortex in the generation of binocular depth perception.Dorsal visual areas appear to use a computational strategy based on a simple algorithm that approximately measures the cross-correlation between image regions on the left and right eyes. Ventral visual areas appear to use a more sophisticated algorithm that makes point-for-point matches between specific features on the left and right retinas.Binocular depth perception has been recently studied at the neuronal level using the measurement of choice probabilities and the application of electrical microstimulation within selected parts of the visual cortex.The identification of a significant role for the extrastriate visual cortex in the generation of binocular depth perception leads to a broadened interest in the roles of these areas in explaining some phenomena associated with the human clinical condition of amblyopia.

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