Autonomous cortical rhythms affect temporal modulation transfer functions

A correlational study between the dominant frequencies in the spontaneous local field potential and the single unit's best modulation frequency (BMF) for periodic click train stimulation in the primary auditory cortex of the cat is presented. Data were obtained from 251 single units recording in 29 cats. The correlation between spindle frequency (mean 8.2 Hz) and BMF (mean 9.3 Hz) was significant (r(2) = 0.58, P < 0.0001). The limiting click-following rate was negatively correlated with the strength of the spindle rhythm: the longer the oscillation the lower the limiting rate. This suggests that the click-following response of the primary auditory cortex depends as much on ongoing autonomous activity as it does on stimulus-induced activity.