Olfactory Modulation of Steady- State Visual Evoked Potential Topography in Comparison with Differences in Odor Sensitivity

Abstract

Summary Research was undertaken to determine whether olfactory stimulation can alter steady-state visual evoked potential (SSVEP) topography. Odor-air and air-only stimuli were used to determine whether the SSVEP would be altered when odor was present. Comparisons were also made of the topographic activation associated with air and odor stimulation, with the view toward determining whether the revealed topographic activity would differentiate levels of olfactory sensitivity by clearly identifying supra- and subthreshold odor responses. Using a continuous respiration olfactometer (CRO) to precisely deliver an odor or air stimulus synchronously with the natural respiration, air or odor (n-butanol) was randomly delivered into the inspiratory airstream during the simultaneous recording of SSVEPs and subjective behavioral responses. Subjects were placed in groups based on subjective odor detection response: “yes” and “no” detection groups. In comparison to air, SSVEP topography revealed cortical changes in response to odor stimulation for both response groups, with topographic changes evident for those unable to perceive the odor, showing the presence of a subconscious physiological odor detection response. Differences in regional SSVEP topography were shown for those who reported smelling the odor compared with those who remained unaware of the odor. These changes revealed olfactory modulation of SSVEP topography related to odor awareness and sensitivity and therefore odor concentration relative to thresholds.

Flavour sensory qualities and consumer perceptions – a comparison of sensory and brain activity responses to flavour components in different populations

“…A two-channel odour delivery system with removable syringes was used in the study. This continuous respiration olfactometer (CRO) was devised for use with brain electrical recording techniques to monitor changes in brain electrical activity associated with odour responses induced during natural respiration (Owen, 1998). The CRO delivers odour or control synchronous with each inspiration by closely monitoring the subject's natural respiratory cycle, using a pneumotachograph mounted on a facemask with a two-way non-rebreathing valve.…”

“…It is clear that some aspects of brain electrical activity changes must relate to processing of a flavour or odour. It has been established that electroencephalographic (EEG) recordings alter when an odour is present or when the concentration of an odour is altered (Lorig et al, 1991;Schwartz et al, 1992;Brauchli et al, 1995;Pause et al, 1996;Tateyama et al, 1997;Owen, 1998Owen, , 2002aPatterson et al, 1998;Kline et al, 2000), and even when the individual is not consciously aware of the presence of the odour (Lorig & Schwartz, 1988;Lorig et al, 1990;Lorig, 1994;Owen, 1998). There is also evidence that the nature of some components of the EEG differ between those who like an odour compared with those who dislike the odour (Van Toller, 1988;Klemm et al, 1992;Miltner et al, 1994;Kline et al, 2000;Owen & Patterson, 2002).…”

“…, 2000), and even when the individual is not consciously aware of the presence of the odour (Lorig & Schwartz, 1988; Lorig et al. , 1990; Lorig, 1994; Owen, 1998). There is also evidence that the nature of some components of the EEG differ between those who like an odour compared with those who dislike the odour (Van Toller, 1988; Klemm et al.…”