ON DETERMINANTS OF FIRST-SPIKE LATENCY IN AUDITORY-CORTEX

The first-spike latency of neurones at any level of the auditory pathw ay decreases with stimulus amplitude. As stimuli are generally shaped with rise functions to avoid spectral splatter, a common interpretatio n of the latency decrease is that the amplitude of the signal reaches the neurone's firing threshold earlier during the rise time. We demons trate here, for auditory cortex neurones and by varying the amplitude and rise time of tonal stimuli, that this threshold model is inadequat e to account for the observed latency changes, particularly when adapt ive processes are taken into account. The data raise the possibility t hat latency may be a function of other properties associated with a si gnal's onset, such as rate change of peak pressure.