Hippocampal auditory evoked response threshold in the rat: behavioral modulation.
Summed auditory evoked responses (AERs) were recorded bipolarly from CA1 field and inner molecular layer of the dentate gyrus of the hippocampus (Hipp) and compared to AERs simultaneously recorded from other extralemniscal (EL) nuclei and the inferior colliculus (IC) in the rat. There were no significant threshold differences for early Hipp AER (EHAER) and other EL AERs. The threshold for EHAERs and other EL AER was by several tens of decibels above that for IC, but usually lower than that for eliciting muscular reflexes. Actual behaviour (still waking, drowsiness, exploration, attention to stimuli) modified the thresholds for EHAER and other EL AERs equally. There was only little effect of actual behavior upon nonthreshold modulation of amplitudes of EHAERs. It is assumed that setting the threshold of the hypothetical common source of EH and other EL AERs plays main role in their behavioral modulation. As supposedly EHAERs are mediated through the perforant path, our results suggest that this pathway might transmit information related to high-threshold diffuse activation of the brain during the early stage of auditory processing.
Jirsa
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Department of Psychophysiology, Institute of Physiology, Videnska, Czechoslovakia.
Poc
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Radil
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D000161:Acoustic Stimulation; D000818:Animals; D001288:Attention; D001309:Auditory Threshold; D001522:Behavior, Animal / Q000502:physiology*; D005072:Evoked Potentials, Auditory; D005106:Exploratory Behavior; D006624:Hippocampus / Q000166:cytology / Q000502:physiology*; D008297:Male; D051381:Rats; D014851:Wakefulness