The sympathetic innervation of the skin primarily subserves thermoregulation, but the system has also been commandeered as a means of expressing emotions. In order to understand the central neural processes involved in emotional processing and the generation of autonomic markers of emotion we recorded skin sympathetic nerve activity (SSNA) concurrently with functional magnetic resonance imaging (fMRI) of the brain at rest in thermoneutral conditions, or while showing subjects neutral or emotionally-charged images from the International Affective Picture System (IAPS). Methods: SSNA was recorded via tungsten microelectrodes inserted into the peroneal nerve in 21 subjects. Gradient echo, echo-planar fMRI was performed using a 3T scanner (Philips Achieva). Two hundred volumes (46 axial slices, TR=8 s, TE=40 ms, flip angle=90 deg, raw voxel size =1.5×1.5×1.5 mm) were collected in a 4s-ON, 4s-OFF protocol. Total sympathetic burst amplitudes were measured during the period between scans. Blood Oxygen Level Dependent (BOLD) changes in signal intensity (SPM5, uncorrected p<0.001) were measured during the subsequent period to account for neurovascular delays. Results: Resting SSNA was positively correlated to signal intensity in the orbitofrontal, frontal and insular cortices on the right side, mid-cingulate and precuneus, and negatively correlated to signal intensity in the left orbitofrontal and left insula. Positive and negative emotionally-charged images evoked significant increases in total SSNA and signal intensity in the orbital, dorsolateral and ventromedial prefrontal cortices, amygdala, nucleus accumbens and anterior insula. Increases in signal intensity during increases in SSNA occurred in a number of brain regions, including the central and lateral amygdala, dorsolateral pons, thalamus, nucleus accumbens, and cerebellar cortex. Signal intensity decreases during emotionally evoked increases in SSNA occurred in the left orbitofrontal, frontal and right precuneus cortices. Conclusions: We have identified structures in the brain differentially engaged in the generation of sympathetic markers of introspection and emotional arousal.
37th Congress of IUPS (Birmingham, UK) (2013) Proc 37th IUPS, PCC135
Poster Communications: Identification of sites of sympathetic outflow at rest and during emotional arousal: concurrent recordings of skin sympathetic nerve activity and fMRI in humans
V. G. Macefield1,2, C. James1, L. A. Henderson3
1. School of Medicine, University of Western Sydney, Sydney, New South Wales, Australia. 2. Neuroscience Research Australia, Sydney, New South Wales, Australia. 3. Discipline of Anatomy & Histology, University of Sydney, Sydney, New South Wales, Australia.
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