Single unit activity vs. amplitude of the epidural evoked potential in primary auditory cortex of awake cats

The study investigated, in primary auditory cortex (AI) of awake cats, the relationship over a range of stimuli between the amplitude and latency of the initial positive deflection (P1) of the primary evoked potential and the intensity of concurrent underlying evoked single unit activity. Epidural evoked potentials and extracellular responses of 155 single units to monaural 100 musec clicks ranging from 45 to 110 dB were recorded. At low stimulus levels, considerable unit response could occur with a very small P1. At middle stimulus levels, unit response was directly proportional to P1 amplitude. At higher stimulus levels, P1 amplitude continued to increase while unit response began to saturate.