The main goal of this project is to better understand the neurophysiology of the motor system and the role of attention in Functional Neurological Disorder (FND) and to explore the physiological effects of a novel non-invasive treatment option for this disorder.
To this end, several methods will be employed: non-invasive brain stimulation (using Transcranial Magnetic Stimulation, TMS), neuroimaging (fMRI), transdermal auricular vagus nerve stimulation (taVNS), clinical assessments and questionnaires.
The study consists of 2 experiments, each with specific objectives.
Primary objective:
The primary objective of this study is to assess the effects of taVNS, as an adjunctive intervention to standard physical therapy, on the quality of life in FND patients.
Secondary objectives:
Experiment 1
- Assess baseline neurophysiological differences of the motor system at rest and under different attentional demands, between FND patients and healthy participants.
- Compare the motor behaviour of the upper limb (index finger) under different attentional demands, in FND patients and healthy participants.
- Explore the role of symptom severity, mood, physical health, and interoception (the perception of bodily signals), assessed by questionnaires, in the modulation of motor system neurophysiology in FND patients and healthy participants.
- Explore the relationship between neurophysiological (point 1) and behavioral (point 2) outcomes, and the outcomes of clinical and psychological scores measured (point 3).
Experiment 2
- Assess the feasibility of the taVNS intervention as an adjunctive treatment in FND.
- Determine whether adding taVNS to standard physical therapy improves clinical outcomes (motor symptoms) in FND patients, assessed by clinical scores (CGI, sFMDRS).
- Explore changes in self-reported measures of mood, stress, physical health and interoception (the perception of bodily signals), assessed by questionnaires, after taVNS in FND patients.
- Explore changes in upper limb strength, measured by a grip strength test with hand-held dynamometer under different starting conditions (pressing freely and pressing after a cue), before, during and after taVNS in FND.
- Assess the effect of taVNS on heart rate and heart rate variability (HRV) in FND patients.
- Analyse the modulation of brain network connectivity via fMRI at rest and during a behavioural task (emotion-motion task), before and after taVNS in FND patients.
- Explore the relationship between neuroimaging (point 6), behavioral (point 2) outcomes, and the outcomes of clinical and psychological scores measured (point 3).
An additional outcome will explore the relationship between the outcomes of Experiment 1 and Experiment 2 to assess the prognostic potential of the outcomes of Experiment 1.