PET‐based investigation of cerebral activation following intranasal trigeminal stimulation

Abstract

The present study aimed to investigate cerebral activation following intranasal trigeminal chemosensory stimulation using O15-H2O-PET. A total of 12 healthy male participants underwent a PET scan presented with four scanning conditions; two left-sided intranasal CO(2)-stimuli and two matched baseline conditions consisting of odorless air. CO(2) was used as it produces burning and stinging sensations. Stimulation started 20 s before intravenous injection of the isotope and lasted for the first 60 s of the 5 min scan time. A comparison between CO(2) and baseline showed a pronounced activation of the trigeminal projection area at the base of the postcentral gyrus (primary and secondary somatosensory cortex) which was more intense for the right hemisphere, contralateral to the side of stimulation. In addition, activation was also found in the piriform cortex which is typically activated following odor presentation and thus thought of as primary olfactory cortex. In conclusion, and in line with previously published work, our data suggest that intranasal trigeminal stimulation not only activates somatosensory projection areas, but that it also leads to activation in cerebral areas associated with the processing of olfactory information. This may be interpreted in terms of the intimate relation between the intranasal chemosensory systems.

Model-free fMRI group analysis using FENICA

“…Most odorants are known to affect both the trigeminal and the olfactory systems (Doty et al, 1978). Applying CO 2 to the nasal mucosa is known to activate areas involved in the processing of chemosensory signals as well as brain areas known to be engaged in handling painful stimuli (Iannilli et al, 2008;Boyle et al, 2007;Hummel et al, 2005Hummel et al, , 2009.…”

Cortical Hemodynamic Responses to Intravenous Thiamine Propyldisulphide Administration Detected by Multichannel Near Infrared Spectroscopy (NIRS) System

“…Experimentally, several functional imaging studies, using positron emission tomography (PET) (Dade et al 1998;Zald and Pardo 2000;Savic and Gulyas 2000;Hummel et al 2009), functional magnetic resonance imaging (fMRI) (Levy et al 1999;Weismann et al 2001;Wang et al 2005), magnetoencephalography (MEG) (Tonoike et al 1998;Walla et al 2002;Miyanari et al 2006;Boesveldt et al 2009) and electroencephalography (EEG) (Tateyama et al 1998;Laudien et al 2006Laudien et al , 2008, had been performed to detect objective olfactory brain responses. In these studies, the orbitofrontal cortex, entorhinal cortex, hippocampus, insular cortex, hypothalamus, piriform cortex, amygdala, and anterior cingulate cortex were reported to be activated by olfactory stimulation.…”

The neuronal correlates of intranasal trigeminal function—an ALE meta-analysis of human functional brain imaging data

“…Several comparisons of brain activation originating from stimulation with pure trigeminal stimuli to activation originating from stimulation with pure odorants have demonstrated considerable overlap in the structures mediating functional processing in each system (Boyle et al, 2007; Hummel et al, 2005; Hummel et al, 2009a; 2009b; Iannilli et al, 2008; Schoepf et al, 2009). Whereas pure trigeminal stimuli typically activate the brain stem, thalamus, caudate nucleus, anterior and dorsolateral orbitofrontal cortex, medial frontal gyrus, frontal operculum, superior temporal gyrus, cingulate, and the postcentral gyrus, stimulation with pure odors commonly induces activation in the medial orbitofrontal cortex, amygdala, parahippocampal gyrus, and cerebellum, exclusively.…”

“…Whereas pure trigeminal stimuli typically activate the brain stem, thalamus, caudate nucleus, anterior and dorsolateral orbitofrontal cortex, medial frontal gyrus, frontal operculum, superior temporal gyrus, cingulate, and the postcentral gyrus, stimulation with pure odors commonly induces activation in the medial orbitofrontal cortex, amygdala, parahippocampal gyrus, and cerebellum, exclusively. Functional overlaps between the trigeminal and olfactory networks were observed in the piriform cortex, the medial orbitofrontal cortex, peri-insular regions, as well as secondary somatosensory cortex (Boyle et al, 2007; Hummel et al, 2009b). Additional evidence for a close connection between the two chemosensory systems arises from comparisons of normosmic with anosmic subjects: trigeminally-mediated information is processed differently in the presence or absence of an intact sense of smell (Frasnelli and Hummel, 2007; Frasnelli et al, 2007; Hummel et al, 1996; Iannilli et al, 2007).…”