Martin, G. Neil (1994) Pre- and post-prandial human scalp-EEG response to olfactory stimulation, using the brain electrical activity mapping technique. PhD thesis, University of Warwick.

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Abstract

Recent psychophysiological evidence indicates that Central Nervous System activity may be directly affected by olfactory stimulation. The present thesis sought to examine the relationship between the CNS and olfactory perception in a series of three EEG experiments employing food odours as stimuli. Further aims were to explore the effect of food ingestion on psychophysiological behaviour and on the hedonic rating of odours, and to investigate the relationship between odour's affective valence and EEG asymmetry. The areas relating to olfactory psychology are reviewed in detail. Experiment 1 investigated the effects of the ingestion of a lunchtime meal and ambient food odour on the auditory oddball evoked potential. Marked P2(K) amplitude changes were associated with exposure to odour. In most cases, decreases in amplitude were obtained depending on the nature of the stimulus. Effects of meal ingestion were also found for P2(X) with the lunch group showing greater amplitude during the second (post-prandial) session than the unfed control group. A three-way interaction was obtained with the controls showing a significant decrease in P2(X) amplitude during the presentation of the odour of vegetable in the second session in comparison to the lunch group. No effect of odour on P300 amplitude was found. Experiments 2 and 3 examined EEG response to a variety of different actual and synthetic food odorants. Both experiments showed alterations in the theta frequency (in experiment 2, exclusively so). The effect of meal ingestion was variable with controls showing greater alpha activity than the lunch group during the second session in one experiment, but the opposite effect in the other. No alpha-related EEG asymmetry for pleasant or unpleasant odours was found in experiment 2 although asymmetries were obtained for the theta frequency. In experiment 3, however, intra-hemispheric alpha asymmetry was obtained for the most pleasant odour. No effect of lunch was found for the postprandial psychometric rating of food odour suggesting that negative olfactory alliesthesia may not be as robust a phenomenon as gustatory alliesthesia. The hypothesis is put forward that the dominant EEG frequency for the processing of olfactory information is the theta frequency. It is suggested, however, that the effects found in this waveband may be related to the psychometric properties of the odour such as distractability and not due to the odour per se.

Item Type:	Thesis or Dissertation (PhD)
Subjects:	B Philosophy. Psychology. Religion > BF Psychology
Library of Congress Subject Headings (LCSH):	Smell -- Psychological aspects, Psychophysiology, Electroencephalography, Olfactory sensors, Olfactory receptors, Food -- Odor -- Psychological aspects, Food -- Sensory evaluation
Official Date:	February 1994
Dates:	Date Event February 1994 Submitted
Institution:	University of Warwick
Theses Department:	Department of Psychology
Thesis Type:	PhD
Publication Status:	Unpublished
Supervisor(s)/Advisor:	Rippon, Gina
Sponsors:	Agricultural and Food Research Council (Great Britain) ; Quest International
Extent:	xv, 282, [83] leaves : illustrations
Language:	eng

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