Transient responses in area MT facilitate speed change detection A Traschütz, A K Kreiter, D Wegener |
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Institute for Brain Research, University of Bremen, Germany
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| In a recent study, we found that reaction times in a speed change detection task closely correlate with the latency of transient responses in area MT. Here, we investigate how these transient responses are related to the sign and amplitude of a wide range of positive and negative speed changes, and how they depend on the underlying speed tuning. We find that transient rate changes do not simply reflect the neuron’s speed tuning, but depend on a multiplicative gain which scales the response according to the speed change amplitude. The strength of this gain correlates with a measure of short-term adaptation, suggesting a computational mechanism at the network level. We show that speed change detection at or even above the behavioral level can be explained by a simple, physiologically plausible threshold model based on the summed input of a limited number of both optimally and non-optimally speed-tuned neurons. Moreover, we show that transient response amplitudes and latencies can explain a recently identified eccentricity-dependent detection bias. We present a unifying explanation regarding the difference between detection thresholds and reaction times in their relation to speed change amplitudes, which may be extended to detection of rapid changes in visual input in general. |
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