Neural mechanisms involved in odor pleasantness and... : NeuroReport (original) (raw)

CHEMICAL NEUROSCIENCE

Neural mechanisms involved in odor pleasantness and intensity judgments

1Montreal Neurological Institute, McGill University, Montreal, Canada

2Laboratoire de Neurosciences et Systèmes Sensoriels CNRS and Université Claude Bernard, Lyon, France

3Corresponding Author: Robert J. Zatorre

Acknowledgements: We gratefully acknowledge the assistance of Dr A.C. Evans and the staff of the McConnell Brain Imaging Center, and of the MNI Cyclotron Unit. The research was supported by grants from the Medical Research Council of Canada and from the G.I.S. Sciences de la Cognition, France.

Received 26 April 2000; accepted 13 June 2000

Abstract

Olfactory processing in the human brain was examined using positron emission tomography. Twelve normal volunteers were scanned while smelling pairs of odors: they were asked to judge which odor was more pleasant in one condition, and which was more intense in a second condition; they also were scanned while sniffing an odorless stimulus. As in prior studies, greater cerebral blood flow was found in the right orbitofrontal cortex during both pleasantness and intensity judgments as compared to baseline. Cerebellar activity was also seen, but contrary to expectations no activity was detected in the primary olfactory (piriform) cortex. Only the pleasantness judgment elicited additional activity within the hypothalamus, suggesting that this structure may be involved in affective processing that requires access to information about internal state.