ELECTROPHYSIOLOGY AND MORPHOLOGY OF NEURONS IN RAT PERIRHINAL CORTEX

The intrinsic membrane properties of perirhinal cortical neurons were studied by intracellular recording in in vitro rat brain slices. Gross morphology was also examined through injection of the fluorescent dye carboxyfluorescein. The cells encountered displayed a diversity of el ectrophysiological properties, and were similar to cells reported in o ther neocortical areas with regard to spiking patterns, afterpotential s, and morphology. However, very few (4%) intrinsically bursting neuro ns were encountered. Two pyramidal cells with thick apical dendrites w ere filled, and both fired doublets of action potentials for their fir st suprathreshold events. Of the filled pyramidal cells with thin apic al dendrites, most (9/11) fired single action potentials for their fir st suprathreshold events. A variety of classification schemes were use d to group the data, and several schemes were found to be equally succ essful. According to one of the schemes, cells recorded with carboxyfl uorescein filled electrodes had significantly greater action potential widths at half-amplitude and more depolarized resting potentials than cells recorded without this dye.