A spatiotemporal comparison between olfactory and trigeminal event-related potentials

The present study compared the temporal and spatial aspects of human olfactory and trigeminal processing. A relatively selective trigeminal stimulus, CO2, and a relatively selective olfactory stimulus, H2S, were delivered with an olfactometer to young, healthy volunteers. The analysis was performed in a classical (5-electrode, main ERPs peaks) and modern approach (high topographical resolution, inverse solution, source localization). Results of microstate segmentation highlighted 5 maps that generally described the two processes at cerebral level. The trigeminal response differed from the olfactory response up to 300 ms after stimulus onset. In this time range, source analysis pointed out that the olfactory stimulation involved olfactory related areas, while trigeminal stimulation involved noxious/somatosensory specific brain areas. Moreover, from 300 ms on our data showed a similarity between the two processes. Statistical parametrical mapping of the differences between conditions suggested greater activation in a specific motor/sniffing network for the CO2 stimulation (probably related to a regulation of the potential noxious stimulus) and a greater activation of the ipsilateral primary olfactory cortex for H2S.

► The present studies human olfactory and trigeminal processing in comparison. ► EEG-high-density channels technique has been used. ► Classical ERPs, microstate segmentation and source analysis has been implemented. ► Differences between the two processes were evident up to 300 ms. ► After it olfactory and trigeminal systems produced similar maps. ► This time breaking point between the two processes is a novelty.