Figure 4.
Ongoing response is sensitive to strychnine application. A, Dot raster display of one neuron stimulated with pure tones at BF (700 Hz). Shown are responses for 10 repetitions at ITDs between ±1 ms without (left; control) and in the presence of strychnine (right). Time axis refers to start of stimulation; stimulus duration was 100 ms (including 5 ms rise/fall time). Spikes that fell into the time window for ongoing response (gray rectangle) are shown in blue and red for control and strychnine condition, respectively. Spikes within the first 10 ms of each spike train were discarded and are shown in black. B, ITD functions for ongoing response only, derived from spikes shown in color in A. Compared with control condition (blue line), the response distribution during strychnine application (red line) was significantly shifted toward the “left” (red asterisk). Several minutes after the strychnine application was terminated, the best ITD was shifted back to more positive ITD values (to the “right”; recovery, gray line). The gray bar marks “physiological range” of ITDs. C, The mean phase angle of the phase-locked ongoing responses was also affected by blocking inhibition. At contralateral leading ITDs in the range of +100 to +400 μs, neuronal responses phase-locked to significantly smaller mean phase angles during strychnine application (dashed red line; left y-axis) than under control condition (dashed blue line); hence, during blockade of inhibition, the response occurred slightly earlier in each pure tone cycle. Phase-locking was high before and during strychnine application (solid blue and red lines, respectively; right y-axis). *p < 0.05; **p < 0.001.