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Max Snodderly, Moshe Gur; Evidence for a motion-selective pathway from V1 to the ventral cortical stream for object recognition. Journal of Vision 2006;6(6):108. doi: 10.1167/6.6.108.
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© ARVO (1962-2015); The Authors (2016-present)
Most authors have found direction selectivity in V1 of macaques primarily in the magno-influenced layers 4Ca, 4B, and 6. Recently, we reported that direction selectivity is more widely distributed and we have proposed a new motion-selective pathway from V1 to the ventral cortical stream that is critical for object recognition. We analyzed the characteristics of V1 neurons in alert monkeys 385–695 µm below the cortical surface, which should selectively sample layer 3. Extracellular responses to sweeping bars were recorded in 23 microelectrode penetrations while monkeys performed a fixation task. 13/31 cells were direction selective. All layer 3 cells had small classical receptive fields, sharp orientation tuning curves, and almost no spontaneous activity. Direction selective cells had smaller CRFs than the non-directional cells and they were predominantly end-stopped. Cells more superficially located in layer 2 demonstrated less selective response properties and the layer 2 cells were not direction selective. These are the first physiological data to differentiate layer 2 and layer 3 in primate visual cortex. Our results are consistent with the concept of parallel pathways coding direction selectivity in V1. One pathway dominated by magno inputs passes through layers 4Ca and 4B to join the dorsal “where” stream, and another pathway combining parvo and magno inputs passes through 4Cm and 3 to join the ventral “what” stream. This new, ventrally-directed pathway, is capable of fine-grained motion analysis that could contribute to perceiving subtle motions within objects such as faces, solving the aperture problem, and perceiving structure from motion.
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