Neurological Representations of Galvanic Skin Response Under 7T fMRI. A Pilot Study.
Poster No:
1359
Submission Type:
Abstract Submission
Authors:
Zachary Cohen1, Mirja Steinbrenner2, Rishi Sharma1, Rory Piper1, Neo Baker1, Mark Richardson3, David Carmichael1
Institutions:
1King's College London, London, United Kingdom, 2Department of Neurology, Charité, Berlin, Germany, 33Department of Basic and Clinical Neuroscience, London, United Kingdom
First Author:
Co-Author(s):
Introduction:
Galvanic skin response (GSR) represents sympathetic arousal [1]. In an inverse relationship the increase of GSR leads to a decrease in cortical excitability [2]. Furthermore, changes in GSR can lead to regionally increased activity in premotor and supplementary motor cortices [3], [4]. The modulation of GSR has been explored as a potential therapy for epilepsy [5]–[8]. However, an incomplete understanding of the acute effects of GSR limits its potential application. This study utilised the increased spatial resolution and sensitivity of 7T MRI to investigate the neurological representations of GSR signal during functional magnetic resonance imaging (fMRI).
Methods:
Seven healthy controls attended St Thomas' Hospital (London, UK) for two study sessions. In the first session, they received GSR modulation training. Electrodes were placed on their fingers and connected to a BrainAmp ExG amplifier. The GSR signal was recorded (BrainVision) and downsampled to 10Hz. Increases in GSR were represented in a game where a bird's height increased. Participants played this game for 1.5 hours with breaks.
In the second session, participants underwent scans using a 7T MRI (Terra Siemens Healthineers), acquiring 0.65mm isotropic structural MP2RAGE images [9] and 220 echo-planar images (1.1mm isotropic, TR=2600ms, TE=24ms) per run. They underwent two fMRI runs of 9 minutes, alternating between rest and attempting to increase GSR in 1 minute blocks. Additionally they tapped their right index finger to their thumb at 1hz in randomised minute blocks. Instructions were given via lights on a screen. Data was processed in Statistical Parametric Mapping (SPM), including realignment, normalisation, and smoothing (12mm kernel). The Functional Image Artifact Correction Heuristic (FIACH) tool for R [10] was used to provide a noise model from signal time courses in brain regions with high noise levels. GSR data was recorded on MR conditional Brain Products equipment.
The GSR signal was convolved with a standard hemodynamic response function in SPM. A General Linear Model analysed three conditions: attempted GSR increase, finger tapping, and actual GSR-signal. T-contrasts were generated at the first level; a second level analysis determined the group effect. Resultant maps were superimposed onto normalized individual echo planar images and a standard Montreal Neurological Institute (MNI) template brain for group analysis, comparing individual and group neural activity in response to the experimental conditions.
In the second session, participants underwent scans using a 7T MRI (Terra Siemens Healthineers), acquiring 0.65mm isotropic structural MP2RAGE images [9] and 220 echo-planar images (1.1mm isotropic, TR=2600ms, TE=24ms) per run. They underwent two fMRI runs of 9 minutes, alternating between rest and attempting to increase GSR in 1 minute blocks. Additionally they tapped their right index finger to their thumb at 1hz in randomised minute blocks. Instructions were given via lights on a screen. Data was processed in Statistical Parametric Mapping (SPM), including realignment, normalisation, and smoothing (12mm kernel). The Functional Image Artifact Correction Heuristic (FIACH) tool for R [10] was used to provide a noise model from signal time courses in brain regions with high noise levels. GSR data was recorded on MR conditional Brain Products equipment.
The GSR signal was convolved with a standard hemodynamic response function in SPM. A General Linear Model analysed three conditions: attempted GSR increase, finger tapping, and actual GSR-signal. T-contrasts were generated at the first level; a second level analysis determined the group effect. Resultant maps were superimposed onto normalized individual echo planar images and a standard Montreal Neurological Institute (MNI) template brain for group analysis, comparing individual and group neural activity in response to the experimental conditions.
Results:
For the condition of GSR modulative increase, we found association of increased activation in attention-network related areas of the brain – specifically left frontal (p<0.001 unc). At the group level these findings were not significant in our number of participants (p<0.001 unc). Expected increases in activity of the left motor area were seen in all individuals and at the group level (p<0.001 unc). During periods of increasing GSR signal we observed increased bilateral frontal pole activation at a group level (T = 5.2 p<0.001 unc) (Fig1).
Conclusions:
GSR modulation shows promise as a therapy for neurological and neuropsychiatric disorders, potentially reducing cortical excitability and influencing sensorimotor activity. This study aims to explore the acute effects of GSR modulation using a novel paradigm in conjunction with 7T MRI fMRI. Despite the small numbers, a prefrontal increase in activity with increasing GSR is consistent with previous literature suggesting altered frontal pole activity [5] This research establishes the feasibility for both additional healthy controls and participants with GGE to be scanned under this paradigm, interrogating if a GSR modulative increase causes reduced sensorimotor connectivity that may be associated with a reduction in seizures.
Brain Stimulation:
Non-Invasive Stimulation Methods Other 2
Modeling and Analysis Methods:
Activation (eg. BOLD task-fMRI) 1
Novel Imaging Acquisition Methods:
Anatomical MRI
BOLD fMRI
Imaging Methods Other
Keywords:
Computational Neuroscience
Epilepsy
fMRI CONTRAST MECHANISMS
FUNCTIONAL MRI
Other - Neuromodulation, Galvanic Skin Response
1|2Indicates the priority used for review
·'Brain activations for each task condition'
Provide references using author date format
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