Journal of Neuroscience, Vol 8, 3869-3878, Copyright © 1988 by Society for Neuroscience
Control of sensory activation of granule cells in the fascia dentata by extrinsic afferents: septal and entorhinal inputs
TC Foster, RE Hampson, MO West and SA Deadwyler
Department of Physiology and Pharmacology, Bowman Gray School of Medicine of Wake Forest University, Winston-Salem, North Carolina 27103.
Three groups of rats were trained to perform a differential discrimination
task in a 2-tone operant conditioning paradigm. One group received
electrolytic lesions of the medial septal nuclei, another received
electrolytic or knife cut lesions of the entorhinal cortex. These groups
were compared with a normal control group. Recordings of granule cells in
the fascia dentata were obtained in all animals during criterion
performance of the behavioral task. Both lesions produced disruption of
behavioral discrimination in the form of increased error and intertrial
responding. Granule cell discharges to the tone stimuli were disrupted by
each type of lesion. Septal lesions reduced the differential discharge
tendency to CS+ and CS- and changed granule cell firing on all trials to
statistically resemble firing on CS- trials in normal animals. Extensive
lesions in the entorhinal cortex or knife cuts that severed the perforant
path caused near elimination of the tone-evoked discharges to both the CS+
and CS-tones. Septal and entorhinal lesions caused marked changes in the
sequential dependence of the granule cell discharge compared with intact
animals. Results are discussed in terms of the control of the granule cell
discharge by the remaining afferent pathways in each type of lesion
condition.