Figure 1.

Examples of two distinct types of cortical responses to aperiodic click trains. A: Upper: illustration of the stimulus, a Poisson-distributed click train (duration: 5 second, stimulus onset/offset times: [0.5, 5.5] second). Lower: mean inter-click interval of the click train. (averaged over a moving time window of 200 ms). For clarity, mean inter-click intervals longer than 100 ms are truncated in the plot. The three arrows on the x-axis point to the times where the click train has the three shortest mean inter-click intervals (also marked on the x-axis of B and C). B: Dot raster of the response of an example primary auditory cortex (A1) neuron to 50 repetitions of the click train stimulus shown in A. This neuron exhibits time-locked firings to many individual clicks. C: Dot raster of the response of another example A1 neuron (same format as in B). This neuron only fires at selective times when inter-click intervals are sufficiently short. Data are from Lu et al. (2001).