Figure 7.

An example from a waiting period test of the parallel effects of NBQX on CR performance and on the activity of a task-modulated IN cell. This experiment consisted of 260 trials with the two 0.5 μl NBQX injections administered during the 40-trial no-stimulation period that began immediately after 40 preinjection trials. A, Raster plot of IN cell activity during the same experiment. The experiment starts at the top with each row representing one trial, and each dot marking the occurrence of an action potential. The black square on each row corresponds to the onset of the eyeblink in that particular trial. The 40 black squares at the ends of rows correspond to the no-stimulation waiting period. This cell responded with excitation during the CS–US interval followed by a combined excitatory/inhibitory response to the US. Shortly after the first NBQX injection, the firing rate of this cell's activity precipitously declined. When stimulation was resumed, CRs were abolished immediately, baseline activity remained suppressed, and modulation during the CS–US interval was severely reduced whereas the relative excitatory modulation to the US became more distinct. The neuronal activity gradually recovered toward the end of the experiment in parallel with the recovery of behavioral CRs. B–E, Peristimulus histograms of the same IN unit constructed for 40 trials before the injection (B), for 40 postinjection waiting trials when stimulation was paused (C), for 40 postwaiting period trials when stimulation was resumed (D), and for the last 40 trials of the experiment (E). Bin width for histograms in B–E is 20 ms. CS, Onset of conditioned stimulus; US, onset of unconditioned stimulus.