Acoustic responses and plasticity of limbic units in cats

Multiple-unit and single-unit responses to monaurally applied acoustic stimuli were recorded from hippocampal, amygdalar, reticular, and auditory pathway nuclei in awake to study the functional organization of the hippocampus and amygdala in sensory processing and their relation to reticular and auditory systems.

Abstract

Multiple-unit and single-unit responses to monaurally applied acoustic stimuli were recorded from hippocampal, amygdalar, reticular, and auditory pathway nuclei in awake. paralyzed cats. A range of motivationally neutral, 1-sec pure tones or white noise evoked markedly different response forms (excitation or inhibition) or magnitudes within the hippocampus and amygdala as a function of both the laterality of stimulus presentation and the quality (frequency) of the acoustic stimulus. The responses typically had relatively long latencies, and the response durations often outlasted the stimulus periods for several hundred milliseconds. During repetitive stimulation with either pure tones or white noise, responses at recording sites in all regions exhibited magnitude decrements (habituation), dishabituation, and spontaneous recovery, These response changes usually, but not always, occurred in parallel at limbic, reticular, and auditory pathway sites. Some degree of specific information about the environment is thus available to the hippocampus and amygdala, where stimulus effects may be modified by experience. The characteristics of the the units recorded in this study are contrasted to those in previous reports of selectively and persistently responsive limbic units in freely moving subjects presented with motivationally significant stimuli. The functional organization of the hippocampus and amygdala in sensory processing and their relation to reticular and auditory systems is discussed.