| Research Abstract |
The event-related potential (ERP) and neuronal firing in the dorsal hippocampus were recorded together with the ERP at the skull in rats performing an anditory discrimination oddball paradigm.At the skull, the target tone elicited N40, P100, N200 and P450.The non-target, on the other hand, clearly evoked only the P100 component.These findings indicated that the P450 of the rat may correspond to the human P300.
The neuronal firings in the hippocampus were recorded with glass micropipettes.It was revealed that approximately 60 percent of the neurons exhibited a sustained increase in firing frequency during the period 100 ms to 550 ms after the target tone onset.The peak latency of the neuronal activation was about 290 ms, and is earlier than the surface P450 peak.
The hippocampal ERP was recorded with chronically implanted stainless steel electrodes.Positive potentials were pbserved at all electrode sites at the latency of the skull P450.The amplitude of this late positive potential was significantly large in the CA3 region of the hippocampus.
The results indicate that the hippocampus of the ret is involved in the late positive potential generation, and supports the view that the limbic area is one of the brain regions related to the human P300 generation.Other brain regions may also participate in its generation, since the peak latency of the neuronal activity and that of the P450 are different, and the phase reversal was not found in the hippocampus.
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