In the early visual pathway, neurons are sensitive to the size of image elements by their spatial frequency (SF) tuning ( Shapley and Lennie 1985 DeValois RL and DeValois KK 1988) and the preferred SF measured with sinusoidal gratings may shift systematically over time after the stimulus onset ( Bredfeldt and Ringach 2002 Mazer et al. Because selectivity to optic flow patterns has been found in single neurons in higher visual cortical areas, it is of interest to examine whether single neurons in the visual cortex can compute the direction of scale changes. The neural mechanisms underlying such visual perception remain unclear. Although optic flow is an important cue for heading direction and time-to-collision ( Gibson 19), human subjects can perceive expansion motion using scale-change information in the absence of optic flow ( Schrater et al. 2001), containing both optic-flow and scale-change information. When an observer moves forward or when an object moves toward the observer, the retinal image expands ( Wang and Frost 1992 Schrater et al. Thus, motion processing involves cortical response preferences to a variety of motion cues, from simple to complex.įor an observer navigating in the visual environment, the spatial pattern of retinal image changes constantly. Selectivity to complex motion signals, such as optic flow patterns, is found in monkey area MST and ventral intraparietal area ( Britten 2008) or cat lateral suprasylvian cortex ( Kim et al. In monkey area MT or cat anterior ectosylvian visual area, some neurons are able to integrate the individual components of a plaid stimulus to represent the direction of global motion ( Movshon et al. The motion sensitive neurons in V1 send their output to area MT in monkey or area posteromedial lateral suprasylvian cortex in cat, where direction-selective neurons are prevalent ( Dreher et al. In V1, a subpopulation of neurons exhibit direction selectivity ( Hubel and Wiesel 1959, 1968) and speed sensitivity ( Orban et al. Motion processing proceeds from V1 to middle temporal visual area (MT), medial superior temporal area (MST), and several higher cortical areas in the dorsal pathway ( Ungerleider and Pasternak 2003). Motion adaptation, primary visual cortex, scale change, spatial frequency, spectrotemporal receptive field Introductionĭetecting the direction and speed of moving objects is crucial for an animal’s survival. Together, our results suggest that direction sensitivity to scale change in V1 may contribute to motion-in-depth processing. Repetitive stimulation with expansion or contraction motion can decrease the sensitivity to the adapted direction in V1, and the effect can be transferred interocularly, suggesting that intracortical connections may be critically involved in the adaptation. Comparison of the direction sensitivity between V1 and LGN neurons showed that the sensitivity in V1 may originate from LGN neurons. This direction sensitivity can be partly accounted for by the spectrotemporal receptive field of V1 neurons. We found that V1 neurons exhibit direction sensitivity to scale changes, with more cells preferring expansion than contraction motion. Here, we measured the responses of cat V1 and the lateral geniculate nucleus (LGN) neurons to a sequence of random images whose spatial frequency spectrum changed over time (i.e., average spatial scale expanded or contracted). The neural mechanisms by which the scale-change information is processed remain unknown. A previous psychophysical study showed that human subjects can perceive expansion motion in texture stimuli that exhibit increases in the scale of image elements but no consistent optic flow pattern. It does not store any personal data.Motion-in-depth causes changes in the size of retinal images in addition to producing optic flow patterns. The cookie is set by the GDPR Cookie Consent plugin and is used to store whether or not user has consented to the use of cookies. The cookie is used to store the user consent for the cookies in the category "Performance". This cookie is set by GDPR Cookie Consent plugin. The cookie is used to store the user consent for the cookies in the category "Other. The cookies is used to store the user consent for the cookies in the category "Necessary". The cookie is set by GDPR cookie consent to record the user consent for the cookies in the category "Functional". The cookie is used to store the user consent for the cookies in the category "Analytics". These cookies ensure basic functionalities and security features of the website, anonymously.
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