HABITUATION OF ODOR RESPONSES IN THE RAT ANTERIOR PIRIFORM CORTEX.
Donald A. Wilson.
Department of Zoology, University of Oklahoma, Norman, OK 73019.
APStracts 4:321N, 1997.
ABSTRACT
Simultaneous recordings of main olfactory bulb (MOB) and anterior piriform
cortex (aPCX) neuron responses to repeated and prolonged odor pulses were
examined in freely breathing, urethane-anesthetized rats. Comparisons of odor
responses were made between multi-unit recordings of MOB activity and single-
unit extracellular and intracellular recordings of Layer II/III aPCX neurons.
Odor stimuli consisted of either 2 sec pulses repeated at 30 sec intervals, or
a single, prolonged 50 sec stimulus. Respiration rate was monitored
throughout. MOB and aPCX neuron responses to odor were quantified both through
firing frequency and through the temporal patterning of firing over the
respiratory cycle. The results demonstrate that aPCX neurons habituate
significantly more (faster) than MOB neurons with both repeated and prolonged
stimulation paradigms. This enhanced habituation is expressed as both a
decrease in aPCX firing despite maintained odor-evoked MOB input, and as a
decrease in aPCX respiratory cycle entrainment despite maintained MOB cyclic
input. Intracellular aPCX recordings suggest that several mechanisms may be
involved in this experience-induced change in aPCX function, including: 1)
decreased excitatory drive of aPCX neurons, 2) decreased excitability of aPCX
neurons, and/or 3) enhancement in odor-evoked inhibition of aPCX neurons.
These studies provide the initial basis for understanding the mechanisms of
non-associative plasticity in olfactory cortex.
Received 2 September 1997; accepted in final form 11 November 1997.
APS Manuscript Number J722-7.
Article publication pending J. Neurophysiol.
ISSN 1080-4757 Copyright 1997 The American Physiological Society.
Published in APStracts on 12 December 1997