Objectives: Mechanical Affective Touch Therapy (MATT) is a safe, novel form of noninvasive peripheral nerve stimulation. Although mechanical stimulation activates nerves, we know little about its impact on psychiatric symptoms and their underlying cortical mechanisms. We examined the effects of open-label MATT on resting state functional connectivity (RSFC) and its relationship with anxiety and affective symptomatology (clinical results in separate report).
Materials and methods: A total of 22 adults with an Axis I anxiety disorder were recruited from the community. After two initial sessions assisted by research staff, participants self-administered 20-minute sessions of MATT at home at least twice daily for four weeks. Self-report measures of mood and anxiety severity were collected at baseline, two weeks, and four weeks. Resting state functional magnetic resonance imaging was collected before the initial MATT session (n = 20), immediately after the first session (n = 18), and following four weeks of MATT (n = 14). Seed-based whole-brain functional connectivity analyses identified brain connectivity patterns correlated with responsiveness to MATT. Seeds were based on Neurosynth meta-analytic maps for "anxiety" and "pain" given MATT's hypothesized role in anxiety symptom amelioration and potential mechanism of action through C-tactile afferents, which play an important role in detecting pain and its affective components. Connectivity results were corrected for multiple comparisons (voxel p < 0.005, cluster p-FDR < 0.05).
Results: Baseline RSFC is predictive of symptom improvement with chronic MATT. Acute increases in insula connectivity were observed between mid-cingulate cortex and postcentral motor regions following the first MATT session. Chronic MATT was associated with increased connectivity between pain and anxiety regions of interest (ROIs) and posterior default mode network (DMN) regions involved in memory and self-reflection; the connectivity changes correlated with decreases in stress and depression symptoms.
Conclusions: MATT is associated with alterations in RSFC in the DMN of anxiety disorder patients both acutely and after long-term administration, and baseline RSFC is predictive of post-treatment symptom improvement.
Keywords: Anxiety disorders; magnetic resonance imaging; mechanical stimulation; neuromodulation; resting state functional connectivity.
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