Olfactory neuronal responses in the primate orbitofrontal cortex: analysis
in an olfactory discrimination task.
Critchley, Hugo D. and Edmund T. Rolls.
University of Oxford, Department of Experimental Psychology, South Parks
Road, Oxford OX1 3UD, Great Britain.
APStracts 2:0354N, 1995.
SUMMARY AND CONCLUSIONS
1. The primate orbitofrontal cortex receives inputs from the primary olfactory
(pyriform) cortex, and also from the primary taste cortex. To investigate how
olfactory information is encoded in the orbitofrontal cortex, the responses of
single neurons in the orbitofrontal cortex and surrounding areas were recorded
during the performance of an olfactory discrimination task. In the task, the
delivery of one of eight different odours indicated that the monkey could lick
to obtain a taste of sucrose. If one of two other odours was delivered from
the olfactometer, the monkey had to refrain from licking, otherwise he
received a taste of saline. 2. 3.1% (48) of the 1580 neurons recorded in the
orbitofrontal cortex had olfactory responses, and 34 (2.2%) responded
differently to the different odours in the task. The neurons responded with a
typical latency of 180 ms from the onset of odorant delivery. 3. 35% of the
olfactory neurons with differential responses in the task responded solely on
the basis of the taste reward association of the odorants. Such neurons
responded either to all the rewarded stimuli, and none of the saline-
associated stimuli, or vice versa. 4. The remaining 65% of these neurons
showed differential selectivity for the stimuli based on the odour quality,
and not on the taste reward association of the odour. 5. The findings show
that the olfactory representation within the orbitofrontal cortex reflects for
some neurons (65%) which odour is present independently of its association
with taste reward, and that for other neurons (35%), the olfactory response
reflects (and encodes) the taste association of the odour. The additional
finding that some of the odour responsive neurons were also responsive to
taste stimuli supports the hypothesis that odour-taste association learning at
the level of single neurons in the orbitofrontal cortex enables such cells to
show olfactory responses which reflect the taste association of the odour.
Received 6 February 1995; accepted in final form 25 October 1995.
APS Manuscript Number J76-5.
Article publication pending J. Neurophysiol.
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 8 December 95