Differential thresholds of local field potentials and unit discharges in rat auditory cortex

Thresholds for responses to tone bursts in the primary auditory field of pentobarbital-anesthetized rat are significantly lower for local field potentials (5.60 dB+/-1.76 S.E.M.) than for multiple unit discharges (17.80 dB+/-3.17), recorded simultaneously from the same microelectrode. The characteristic frequencies (CFs) of local field potentials provide a good 'predictive' estimate of unit CFs at their higher thresholds. The findings are consistent with the view that local field potentials in the auditory cortex reflect summed synaptic potentials rather than cellular discharges.