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


METHODS
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.
Department of Psychiatry,University of Cambridge,Cambridge,UK.
K
K
Baek
Department of Psychiatry,University of Cambridge,Cambridge,UK.
N
N
Doñamayor
Behavioural and Clinical Neurosciences Institute,Cambridge,UK.
L S
LS
Morris
Department of Psychiatry,University of Cambridge,Cambridge,UK.
D
D
Strelchuk
Department of Psychiatry,University of Cambridge,Cambridge,UK.
S
S
Mitchell
Department of Psychiatry,University of Cambridge,Cambridge,UK.
Y
Y
Mikheenko
School of Clinical Medicine, University of Cambridge,Cambridge,UK.
S Y
SY
Yeoh
Department of Clinical Neurosciences,Addenbrooke's Hospital,Cambridge,Cambridge,UK.
W
W
Phillips
Department of Clinical Neurosciences,Addenbrooke's Hospital,Cambridge,Cambridge,UK.
M
M
Zandi
Cambridgeshire and Peterborough NHS Foundation Trust,Cambridge,UK.
A
A
Jenaway
Department of Psychiatry,University of Cambridge,Cambridge,UK.
C
C
Walsh
Department of Psychiatry,University of Cambridge,Cambridge,UK.
V
V
Voon
D000328:Adult; D001288:Attention / Q000502:physiology*; D001364:Awareness / Q000502:physiology*; D002540:Cerebral Cortex / Q000000981:diagnostic imaging / Q000503:physiopathology*; D003291:Conversion Disorder / Q000000981:diagnostic imaging / Q000503:physiopathology*; D005260:Female; D059907:Functional Neuroimaging / Q000379:methods*; D006801:Humans; D033182:Intention; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D009043:Motor Activity / Q000502:physiology*; D011597:Psychomotor Performance / Q000502:physiology*
Functional magnetic resonance imaging; functional neurological disorder; inferior parietal cortex; intention; voluntary action