INTRACELLULAR IN-VIVO RECORDING OF INFERIOR COLLICULUS AUDITORY NEURONS FROM AWAKE GUINEA-PIGS

Intracellular recordings of identified inferior colliculus (ICc) audit ory neurons, were analyzed in in vivo awake, chronically implanted gui nea-pigs. The passive membrane characteristics as well as the spontane ous and click evoked synaptic potentials and spike activity, were stud ied. The injection of current pulses revealed little, if any, adaptati on and membrane voltage shifts that outlasted the electrical stimuli. The spontaneous action potentials, observed in all the units studied, were of the short-duration type. During wakefulness, spontaneous synap tic potentials of higher amplitude were observed in comparison to the anesthetized preparation as well as an enhanced firing rate. The click evoked synaptic potentials far outlasted the sound (click, 0.1 ms) du ration. The binaural, contralateral and ipsilateral sound stimulation evoked different sequences of synaptic potentials and firing. This was mostly in agreement with studies of extracellular recordings from the ICc, in anesthetized and behaving animals.