Figure 2: (a) A glass extracellular recording microelectrodes for recording population spike was placed in the cell body of CA1 pyramidal neurons. A bipolar stimulating electrode (for “test pulse”) was located in the region of Schaffer-collateral-commissural fibers to stimulate the input to CA1 neurons, and a second electrode (for “prepulse”) was placed in the region of alveus hippocampi in order to establish the recurrent inhibition enhanced (RIE) circuit. DG: dentate gyrus. Stim: stimulus electrode. (b) Representative recordings of effects of sevoflurane (3.0 vol%) on the field population spikes of RIE circuit in dementia model mice (SAM-P8) and control mice (SAM-R1). Triangles indicate peak amplitude of the population spikes.