(A) Cell-attached recording allows for high-quality single-unit isolation. High-pass filtered voltage trace recorded in cell-attached mode in the auditory cortex of an unanesthetized rat. Spikes are easy to identify in the trace after thresholding (gray line). Spike times (dots) are assigned to peaks of suprathreshold segments. Gray squares indicate the positions of stimuli (pseudorandom sequence of 100-ms-long tones of different frequencies and attenuations). Note long time scale compared with other figures. The trace segment on the right shows the last 60 ms of the response to the 7^th stimulus (asterisk).

(B) Spike shape can change significantly in a single neuron. Spike times (dots) are assigned to peaks of suprathreshold segments. The burst in the right panel preceded the single spike shown in the left panel by approximately 5 s. Both examples were tone-evoked, and occurred about 40 ms after stimulus termination. Although such dramatic changes are unusual, cell-attached recording minimizes the probability of both false positives and false negatives in spike detection.