Dynamics of spontaneous and evoked activities of the substructures within the cat inferior colliculus.

The spontaneous EEG and evoked electrical activities (EP) recorded simultaneously and bilaterally from different depths below the dorsal surface of the inferior colliculus (IC), have been systematically analyzed in freely moving cats. Power spectral analysis techniques were employed for evaluating the frequency characteristics of the EEG and EP which were recorded from substructures of the IC. The changes in the electrical activities following local lesions further helped us to understand whether these frequencies represent volume conducted field potentials or local neural activity. It was found that in the IC, high frequency electrical activities up to 1000 Hz are generated locally and recorded with maximal amplitudes in the ventral and ventralmost parts. Following the stimulation, strong amplitude enhancement and frequency stabilization were obtained in 70-80 Hz, 350-400 Hz, and 850-950 Hz frequency ranges.