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Polina Zamarashkina, Dina Popovkina, Anitha Pasupathy; Stimulus and task dependence of response latencies in primate area V4. Journal of Vision 2017;17(10):476. doi: 10.1167/17.10.476.
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© ARVO (1962-2015); The Authors (2016-present)
Latency of neuronal responses is influenced by stimulus saliency and context and can reflect hierarchical processing of visual information. In primate area V4, typical latency from stimulus onset is widely cited to be ~100ms (Schmolesky et al., 1998); however, this value was estimated from 29 units in one anesthetized animal. We examined onset latency in area V4 across multiple datasets gathered from 3 animals in our lab. Data were collected from single, well-isolated neurons in awake primates engaged either in a passive fixation task, as stimuli of different shapes, sizes and surface features were flashed within the receptive field of each neuron, or an active behavioral task, where animals reported their perceptual decision via saccadic eye movement. Thus, we were able to examine the effect of stimulus and task context on the timing of neural signals in V4. For each neuron, response latencies were calculated as the time for the neuronal response to reach half of its maximal value (in contrast, Schmolesky et al. performed Poisson spike train analysis). During passive fixation, V4 latencies ranged from 36ms to 195ms with a median value of 72ms across all neurons (n=291). Response latencies did not change as a function of stimulus shape, but were shorter for larger stimuli: median latencies increased from 51ms to 60ms for a fivefold difference in stimulus size (n=29), and for stimuli that included a surface fill as compared to outlines: median latency = 75ms versus 80ms (n=32). Latencies during fixation were slightly longer than during behavior: median latency = 72ms versus 67ms (p< 0.001, n=161). In conclusion, our results demonstrate that a majority of V4 neurons respond within 70ms of stimulus onset and confirm that V4 response dynamics depend on the visual stimulus as well as behavioral context.
Meeting abstract presented at VSS 2017
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