Electrocortical and Autonomic Alteration by Administration of a Pleasant and an Unpleasant Odor

Abstract

The present study was designed to investigate whether there is a consistent response in ongoing EEG due to repetitive olfactory stimulation. Two odors of different hedonic quality were presented bilaterally to five male subjects at suprathreshold levels. A room-air blank served as the control stimulus. Each odor was presented six times to each subject in each of three sessions. Electrocortical activity, heart rate, skin conductance and breathing cycle were recorded continuously. EEG variables assessed were difference scores of absolute power in the frequency bands theta, alphai, alpha2 and betai at eight locations. Phenylethyl alcohol was rated pleasant, while valeric acid was judged unpleasant. Within 8 s after stimulus release, valeric acid increased alpha2 power, whereas phenylethyl alcohol did not. No further frequency bands were affected by olfactory stimulation. These findings suggest that smelling an unpleasant odor leads to a cortical deactivation. Chem. Senses 20: 505-515, 1995.

Physiological Responses Induced by Pleasant Stimuli

“…Moreover, our results support the hypothesis that visual stimulus-induced positive emotions are related with the left cerebral hemisphere (Davidson, 1992(Davidson, , 1982Tomarken et al, 1992). Furthermore, unfavorable odor-stimulated unpleasant emotion appears to incrementally excite bilateral frontal regions of humans (Kim and Watanuki, 2003;Kline et al, 2000;Brauchli, 1995;Van Toller et al, 1993). Taken together, the data from EEG studies render possible assessments of exogenously stimuli to be interpreted as being pleasant or unpleasant by the brain.…”

Effects of Inhalation of Essential Oils on EEG Activity and Sensory Evaluation.

“…6). Brauchli et al (1995) suggested that olfactory stimulation by an unpleasant odor leads to a stronger cortical deactivation than does such stimulation by a pleasant odor. We expected the effects of odors in relation to positive or comfortable feelings.…”

Power spectra of ongoing activity of the snail brain can discriminate odorants

“…Recently, a number of reports on chemosensory evoked or event-related potentials in mammals have appeared [11,34,37,43,44,50,60]. Some of them report increase of theta and/or alpha activity in EEG during odor application.…”