Impaired awareness of motor intention in functional neurological disorder: implications for voluntary and functional movement

Abstract

BackgroundFunctional neurological disorders (FNDs), also known as conversion disorder, are unexplained neurological symptoms unrelated to a neurological cause. The disorder is common, yet poorly understood. The symptoms are experienced as involuntary but have similarities to voluntary processes. Here we studied intention awareness in FND.MethodA total of 26 FND patients and 25 healthy volunteers participated in this functional magnetic resonance study using Libet's clock.ResultsFND is characterized by delayed awareness of the intention to move relative to the movement itself. The reporting of intention was more precise, suggesting that these findings are reliable and unrelated to non-specific attentional deficits. That these findings were more prominent with aberrant positive functional movement symptoms rather than negative symptoms may be relevant to impairments in timing for an inhibitory veto process. Attention towards intention relative to movement was associated with lower right inferior parietal cortex activity in FND, a region early in the processing of intention. During rest, aberrant functional connectivity was observed with the right inferior parietal cortex and other motor intention regions.ConclusionsThe results converge with observations of low inferior parietal activity comparing involuntary with voluntary movement in FND, emphasizing core deficiencies in intention. Heightened precision of this impaired intention is consistent with Bayesian theories of impaired top-down priors that might influence the sense of involuntariness. A primary impairment in voluntary motor intention at an early processing stage might explain clinical observations of slowed effortful voluntary movement, heightened self-directed attention and underlie functional movements. These findings further suggest novel therapeutic targets.

Corticolimbic fast-tracking: enhanced multimodal integration in functional neurological disorder

“…28 29 Our functional propagation findings suggest that while the left anterior insula may be an important node in the pathophysiology of FND, a network perspective incorporating the impact of abnormal integration of information from the left anterior insula to the right anterior insula, TPJ and motor regions sheds additional light on brainsymptom severity relationships. In addition, tasked-based 6 55 and resting-state neuroimaging abnormalities [23][24][25] in the TPJ/inferior parietal lobule have been characterised in FND cohorts, and linked to impaired motor attention awareness and self-agency. Enhanced insular-TPJ link-step connectivity correlating with symptom severity in our study, and previously described taskbased 55 and functional connectivity alterations 25 across insular and TPJ areas, suggest that these epicentres both play important roles in promoting altered awareness in individuals with FND.…”

“…Anterior portions of the multimodal integration network overlap with the salience network, while posterior areas of this network (eg, TPJ) are implicated in motor intention awareness and action authorship deficits in FND. [23][24][25] Notably, SFC has characterised mechanistic insights in neurologic 26 and neuropsychiatric populations. 27 In this resting-state neuroimaging study, we examined the functional propagation of primary motor (hand, foot, tongue) and amygdalar (laterobasal, centromedial nuclei) regions in 30 patients with motor FND compared with 30 healthy controls.…”

Functional movement disorders

“…Comparing patients when they had their involuntary functional tics to a period where they had a voluntary tremor (order to reproduce their tremor intentionally), fMRI demonstrated a reduced brain activity in the right temporo-parietal junction (TPJ), a key area involved in integrating complex sensory signals [78,79]. The right TPJ plays an important role in the sense of agency, which is the sense that we are the actors of our own actions.…”

Functional Movement Disorders and Placebo: A Brief Review of the Placebo Effect in Movement Disorders and Ethical Considerations for Placebo Therapy

“…Studies using several experimental modalities have suggested an impairment in the sense of agency (SA) in patients with FMDs. Functional magnetic resonance imaging (fMRI) studies have shown decreased functional connectivity between the right temporoparietal junction (a critical region in the SA network) and sensorimotor regions in patients with FMDs compared to healthy controls . In another fMRI study in which a virtual reality paradigm was used to modulate SA for a motor control task in healthy control patients and those with FMD, the FMD group reported greater variability in their perceived level of control, associated with selective disruption of the SA network .…”