Effects of ventral hippocampal long-term potentiation and depression on the gamma-band local field potential in anesthetized rats.

We examined the effect of long-term potentiation or depression (LTP or LTD) on the local field potential, focusing on the gamma-band (40-100 Hz) power, in the ventral hippocampus CA1 of anesthetized rats. LTP and LTD induction in the CA3-CA1 pathway increased the CA1 spontaneous gamma-band power by around 40 and 80-100 Hz, respectively, while neither changed the evoked levels significantly. These results suggest that the ventral CA1 local field potential can maintain bidirectional plasticity in the steady state for the long term. Given the involvement of synaptic plasticity in learning and memory, the gamma-band power change associated with LTP/LTD may relate to ventral hippocampal functions. The LTP increased the spontaneous power at around 40 Hz of the gamma-band frequency in the ventral CA1, and the LTD did the same at 80-100 Hz. The biphasic increase may distribute the subsequent input appropriately to regulate the relevant synaptic history in the ventral CA1 and anatomically related structures in vivo. Copyright 2004 Springer-Verlag