Figure 12.

Directionally selective responses evoked by FM sweeps in an on–off neuron. The tuned region for tone bursts at 50 dB SPL is shown in A. The neuron responded with discharges to FM signals that swept downward from 45 to 15 kHz. Discharges were evoked by downward FM sweeps at all signal durations. The cell failed to discharge to the same FM signals that swept upward from 15 to 45 kHz. Insets show magnified view of synaptic responses to the downward and upward FM sweeps. FM duration is shown by time bars under each record. All FM sweeps were 50 dB SPL, the same intensity as the tone bursts in A that failed to evoked any discharge. All traces of tone burst responses in A were averages of five trials, whereas all FM responses were from single trials. Resting potential was −48 mV.