Mathematics Colloquia and Seminars

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Spike timing and rate convey information about the spatial and temporal features of visual stimuli. Yet, repeated presentations of the same visual stimulus evoke somewhat different responses from one presentation to the next. This trial-to-trial variability in responses to identical stimuli is often assumed to be 'noise' and attributed to unreliable synaptic transmission. Here we examine this assumption for thalamic relay cells. We find that the trial-to-trial variability of spike timing evoked by natural movies does not result entirely from unreliable transmission. Rather a substantial component of this variability reflects the temporal structure of ongoing oscillatory activity in the retina. Our finding has implications for the neural code used by retina and thalamus. That is, visual information may be transmitted by the precise relative timing between neurons rather than absolute spike times.