Abstract
The primary gustatory cortex (GC) is defined as the cortical region that receives fiber projection from the parvicellular part of the ventral posteromedial nucleus in the thalamus. The primary olfactory cortex is defined as the region that receives direct fiber projections from the olfactory bulb. The piriform cortex (PC) is the largest structure in the olfactory cortex and further the piriform region includes the endopiriform nucleus (EPN). In this study, we examined the possibility that the EPN is the region where olfactory and gustatory information are centrally integrated. Electrical and optical recordings were made from slice preparations including PC and GC. Electrical stimulation of the GC evoked a characteristic field potential in the EPN. A field potential was induced in the EPN by stimulation of the PC. Voltage-sensitive dye studies showed that stimulation of the PC induced signal propagation from the PC to EPN, whereas stimulation of the GC did the same from the GC to EPN via the agranular division of the insular cortex (AI). After stimulation of the EPN, optical signals propagated not only to the PC but also to the GC via AI. The olfactory and gustatory pathways appeared to be reciprocally connected. Unit recordings indicated that olfactory and gustatory activity converged onto a single neuron of the EPN. It is suggested that the cortical integration of olfactory and gustatory information could modulate mechanisms involved in food selection and emotional reactions relating to the chemical senses. [Jpn J Physiol 55 Suppl:S160 (2005)]
