Effects of hippocampus-induced prefrontal long-term depression on gamma-band local field potential in anesthetized rats

To determine whether long-term depression (LTD) affects cortical gamma-band local field potential (40-100 Hz), we conducted a LTD induction experiment in the hippocampus-prefrontal cortex (PFC) pathway of an anesthetized rat. The LTD induction increased the spontaneous level of PFC gamma-band power of 70-100 Hz, which was not affected after the long-term potentiation (LTP) induction in our previous experiment. In addition, the LTD induction increased the evoked PFC gamma-band power at 900 ms after hippocampal test stimulation; this latency appeared to differ from that (500-700 ms) observed in our previous LTP experiment. The results indicate that the PFC field potential increases its gamma-band power following both LTP and LTD in the hippocampus-PFC pathway, which is involved in working memory. Particularly, the sustained increase by LTD may reflect a representation of working memory. (C) 2002 Elsevier Science Ireland Ltd. All rights reserved.