Odor and Taste Interaction on Brain Responses in Humans

Abstract

Central neural integration of sensory input from different modalities is a prerequisite for flavor perception. Chemosensory information as part of flavor perception is mediated by (i) specific and (ii) general sensory systems. The mouth and the nose are areas housing specific sensory systems, i.e. the gustatory and the olfactory systems. In the gustatory and olfactory systems, as well as in the vomeronasal organ, information is mediated by chemoreceptors. In the somatosensory system, which is classified here as the general sensory system, chemoreceptors are mainly nociceptors. But there are other modalities present as well, such as mechanoand thermoreceptors. It is commonly accepted that there are plenty of opportunities for the above-mentioned systems to interact. This can happen at several levels of the information processing before reaching the cortical level and even peripheral interactions seem possible. In the psychophysical literature there are numerous demonstrations of taste/smell interactions. However, our understanding of the CNS mechanisms and detailed characteristics thereof are rather limited. In humans, some experiments have recently been published addressing this phenomenon by using imaging technologies (Small et al., 1997, 2004; Cerf-Ducastel et al., 2001; de Araujo et al., 2003; Cerf-Ducastel and Murphy, 2004). We wanted to know if the method of event-related potential (ERP) recording could be a useful tool for the investigation of taste and smell interactions. The reason for this approach is that ERPs have the highest possible time resolution compared to most imaging techniques except magnetic source imaging (MSI). Although we do not report any results here, it has now become possible to obtain information about areas of activation by applying electrical source localization methods based on ERPs. In addition, we have demonstrated that ERP components, namely the N1/P2 portion of the ERP, are generated in the insular cortex (Kettenmann et al., 1997) and also postulated that this area might play a crucial role in integrating taste and smell information. This assumption has been recently supported by Fu et al. (2004).