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, 47 (9), 1624-1636

Impaired Awareness of Motor Intention in Functional Neurological Disorder: Implications for Voluntary and Functional Movement


Impaired Awareness of Motor Intention in Functional Neurological Disorder: Implications for Voluntary and Functional Movement

K Baek et al. Psychol Med.


Background: Functional 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.

Method: A total of 26 FND patients and 25 healthy volunteers participated in this functional magnetic resonance study using Libet's clock.

Results: FND 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.

Conclusions: The 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.

Keywords: Functional magnetic resonance imaging; functional neurological disorder; inferior parietal cortex; intention; voluntary action.


Fig. 1.
Fig. 1.
Libet's clock task. (a) Schematic representation of the task. The red ball revolved around the unnumbered clock face for a maximum of three cycles; participants had to make a button press after waiting one cycle. The ball continued moving for a random interval, after which participants returned the ball to its position when they had felt the urge (W judgement) or actually pressed the button (M judgement). (b) Estimated times of intention (W judgement), movement (M judgement) and difference between intention and movement (W-M) relative to the recorded button press for functional neurological disorder (FND) patients and healthy controls (HV). Values are means, with standard errors represented by the horizontal bars. ++ p = 0.017, * p = 0.009, ** p = 0.001. For a colour figure, see the online version of the paper.
Fig. 2.
Fig. 2.
Attention to intention v. movement. (a) Significant activations associated with attention to intention compared with attention to movement (intention v. movement contrast) across all participants (n = 45). (b) Regions of significantly decreased activity for functional neurological disorder patients (n = 23) compared with healthy volunteers (n = 22) when attending to intention compared with attending to movement. Image displayed at p < 0.005 (uncorrected) for illustration. (c) Results of the correlation between the intention v. movement contrast and the behavioural measure W-M across all participants (n = 45). Image displayed at p < 0.001 (uncorrected) for illustration. pre-SMA, Pre-supplementary motor area; dmPFC, dorsomedial prefrontal cortex; IPL, inferior parietal lobule; dlPFC, dorsolateral prefrontal cortex; IFG, inferior frontal gyrus; M1, primary motor cortex.
Fig. 3.
Fig. 3.
Resting-state functional connectivity from right inferior parietal cortex (IPC) seed. (a) Increased (functional neurological disorder patients > healthy volunteers; FND>HV) and (b) decreased (HV > FND) functional connectivity from IPC to whole brain for FND patients (n = 25) compared with HV (n = 70) during rest. Image displayed at p < 0.005 (uncorrected) for illustration. SMA, Supplementary motor area; IPL, inferior parietal lobule; dlPFC, dorsolateral prefrontal cortex; MTG, middle temporal gyrus; ITG, inferior temporal gyrus; BA, Brodmann area; PCC, posterior cingulate cortex.

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