Impaired sense of agency in functional movement disorders: An fMRI study

Abstract

The sense of agency (SA) is an established framework that refers to our ability to exert and perceive control over our own actions. Having an intact SA provides the basis for the human perception of voluntariness, while impairments in SA are hypothesized to lead to the perception of movements being involuntary that may be seen many neurological or psychiatric disorders. Individuals with functional movement disorders (FMD) experience a lack of control over their movements, yet these movements appear voluntary by physiology. We used fMRI to explore whether alterations in SA in an FMD population could explain why these patients feel their movements are involuntary. We compared the FMD group to a control group that was previously collected using an ecologically valid, virtual-reality movement paradigm that could modulate SA. We found selective dysfunction of the SA neural network, whereby the dorsolateral prefrontal cortex and pre-supplementary motor area on the right did not respond differentially to the loss of movement control. These findings provide some of the strongest evidence to date for a physiological basis underlying these disabling disorders.

Fig 1. Behavioral data contrasting subjective SA with objective control among FMD subjects and controls.

A) Box plots represent median subjective ratings (central line), upper/lower quartiles (box), min/max (whiskers), and outliers (points) for each group and control condition. B) Shows mean/standard error of group subjective ratings along with tendencies to over (positive) or underestimate (negative) control. Asterisks (*) represent significant differences (p < 0.05) between FMD and HV group responses.

Fig 2. Comparison of fMRI responses to the modulation of self-agency in FMD group and controls.

A) Linear trend map of regions responding proportionally to the loss of SA displayed on an inflated standard brain (p < 0.05, corrected). B) Mean BOLD response time courses [% signal change from the mean signal vs. time (sec)] for regions showing proportional responsivity to the level of control as SA was lost in FMD group and controls.