Journal of Neuroscience, Vol 7, 3081-3087, Copyright © 1987 by Society for Neuroscience
Long-term increases in dentate granule cell responsivity accompany operant conditioning
RW Skelton, AS Scarth, DM Wilkie, JJ Miller and AG Phillips
Department of Psychology, University of British Columbia, Vancouver, Canada.
The efficacy of synaptic transmission from the perforant path (PP) to the
granule cells in the dentate gyrus (DG) of freely moving rats was monitored
electrophysiologically over the course of training in an appetitively
motivated, discriminated operant paradigm. Every day, 22 hr after
behavioral sessions, evoked potentials were recorded from the DG following
stimulation of the PP over range of current intensities and the amplitudes
of the population spikes were measured. Behavioral conditions involved
training in an operant conditioning paradigm or a session of free-feeding.
Significant increases in population spike amplitudes were observed over the
8 d of training, but not over the 8 d of free-feeding. This
training-induced increase in granule cell responsivity persisted for at
least 10 d following the cessation of behavioral trials and was in many
ways comparable to long-term potentiation (LTP), subsequently observed in
these same rats 24 hr after tetanic stimulation. These data confirm and
extend previous reports of synaptic enhancements following conditioning and
suggest that such increases in synaptic efficacy may encode some aspect of
learning.