“…This has been confirmed electrophysiologically by showing increases in neuronal firing rates in those structures after acute VNS (Groves et al, 2005) or after long-term stimulation treatment in rats (Dorr and Debonnel, 2006). In humans in vivo, central effects of VNS, usually performed at about 30 Hz, have been studied mostly using electroencephalography (EEG) (Marrosu et al, 2005), positron emission tomography (PET) and single photon emission computer tomography (SPECT) (see (Chae et al, 2003) for a review) and functional magnetic resonance imaging (fMRI) (Bohning et al, 2001;Dietrich et al, 2008;Liu et al, 2003;Lomarev et al, 2002;Nahas et al, 2007;Narayanan et al, 2002;Sucholeiki et al, 2002). Despite a significant variability in reported findings, activations in the medulla/brainstem, limbic regions (insula, anterior cingulate cortex, hippocampus, amygdala, and hypothalamus), thalamus, cerebellum, and periaqueductal grey (PAG) were most commonly observed.…”