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Motor neglect associated with loss of action inhibition.

Coulthard E, Rudd A, Husain M - J. Neurol. Neurosurg. Psychiatr. (2008)

Bottom Line: Using a masked prime task, it was shown that when patients with left motor neglect plan to move their left hand, irrelevant right limb motor programmes intrude, causing delay.Lesion analysis reveals that such asymmetry of motor programming occurs after infarcts of the right putamen and motor association areas.This demonstration of failure to inhibit ipsilesional limb motor plans suggests potential benefit from interventions that might act to restore balance in action planning.

View Article: PubMed Central - PubMed

Affiliation: Institute of Neurology and National Hospital for Neurology and Neurosurgery, 17 Queen Square, London WC1N3AR, UK. l.coulthard@ion.ucl.ac.uk

ABSTRACT
Motor neglect, underuse of one side of the body not explained by weakness or sensory impairment, is a common consequence of stroke that is surprisingly little understood. Behavioural and neuroanatomical hallmarks of the disorder are investigated. Using a masked prime task, it was shown that when patients with left motor neglect plan to move their left hand, irrelevant right limb motor programmes intrude, causing delay. Lesion analysis reveals that such asymmetry of motor programming occurs after infarcts of the right putamen and motor association areas. This demonstration of failure to inhibit ipsilesional limb motor plans suggests potential benefit from interventions that might act to restore balance in action planning.

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Related in: MedlinePlus

Paradigm, behavioural and lesion data. Subjects performed a masked prime task (A). Arrow stimuli subtended approximately 1.5×1°. Neutral primes comprised the arrows rearranged forming a square that carried no directional information (not shown). Twelve blocks of 24 stimuli contained six different trial types randomised with the constraint that each condition occurred the same number of times per block. Hands were covered during the experiment to prevent visual guidance of movement. Subjects were instructed to fixate the laptop display centrally and eye position was monitored by the experimenter. A practice session (<2 min) took place beforehand. Only patients with motor neglect showed significant reaction time delay when a right prime preceded a movement with the left hand (B, red circle). Hence right hand motor plans significantly intrude on left hand movement, but not vice versa, only in patients with motor neglect. Lesions were plotted using MRICro software (www.mricro.com) from either CT or MR. Lesion subtraction (patients with motor neglect minus those without) shows frontal white matter selectively affected in patients with motor neglect (C). (D) Brunner–Munzel statistic revealed that right putamen and subcortical white matter were significantly associated (z scores >4.47) with abnormal performance in the masked prime task using the left, but not the right, hand. (E) Severity of motor neglect is significantly associated (z >4.49) with damage at several discrete areas within the right hemisphere (including white matter near the putamen, inferior frontal gyrus, rolandic operculum and parietal supramarginal gyrus). RT, reaction time; SOA, stimulus onset asynchrony.
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JNN-79-12-1401-f01: Paradigm, behavioural and lesion data. Subjects performed a masked prime task (A). Arrow stimuli subtended approximately 1.5×1°. Neutral primes comprised the arrows rearranged forming a square that carried no directional information (not shown). Twelve blocks of 24 stimuli contained six different trial types randomised with the constraint that each condition occurred the same number of times per block. Hands were covered during the experiment to prevent visual guidance of movement. Subjects were instructed to fixate the laptop display centrally and eye position was monitored by the experimenter. A practice session (<2 min) took place beforehand. Only patients with motor neglect showed significant reaction time delay when a right prime preceded a movement with the left hand (B, red circle). Hence right hand motor plans significantly intrude on left hand movement, but not vice versa, only in patients with motor neglect. Lesions were plotted using MRICro software (www.mricro.com) from either CT or MR. Lesion subtraction (patients with motor neglect minus those without) shows frontal white matter selectively affected in patients with motor neglect (C). (D) Brunner–Munzel statistic revealed that right putamen and subcortical white matter were significantly associated (z scores >4.47) with abnormal performance in the masked prime task using the left, but not the right, hand. (E) Severity of motor neglect is significantly associated (z >4.49) with damage at several discrete areas within the right hemisphere (including white matter near the putamen, inferior frontal gyrus, rolandic operculum and parietal supramarginal gyrus). RT, reaction time; SOA, stimulus onset asynchrony.

Mentions: Here we probe the inhibitory processes involved in motor neglect behaviourally using a masked prime task which offers an important window onto automatic inhibitory control.6 This paradigm has recently been deployed to probe deficits in Parkinson’s disease as well as focal lesions of supplementary motor areas.7 8 In this task, prime arrow stimuli are presented for less than 50 ms and then masked (fig 1A). Normal observers are not able to report having seen the prime. However, the prime influences performance when a subsequent target arrow requires a response.


Motor neglect associated with loss of action inhibition.

Coulthard E, Rudd A, Husain M - J. Neurol. Neurosurg. Psychiatr. (2008)

Paradigm, behavioural and lesion data. Subjects performed a masked prime task (A). Arrow stimuli subtended approximately 1.5×1°. Neutral primes comprised the arrows rearranged forming a square that carried no directional information (not shown). Twelve blocks of 24 stimuli contained six different trial types randomised with the constraint that each condition occurred the same number of times per block. Hands were covered during the experiment to prevent visual guidance of movement. Subjects were instructed to fixate the laptop display centrally and eye position was monitored by the experimenter. A practice session (<2 min) took place beforehand. Only patients with motor neglect showed significant reaction time delay when a right prime preceded a movement with the left hand (B, red circle). Hence right hand motor plans significantly intrude on left hand movement, but not vice versa, only in patients with motor neglect. Lesions were plotted using MRICro software (www.mricro.com) from either CT or MR. Lesion subtraction (patients with motor neglect minus those without) shows frontal white matter selectively affected in patients with motor neglect (C). (D) Brunner–Munzel statistic revealed that right putamen and subcortical white matter were significantly associated (z scores >4.47) with abnormal performance in the masked prime task using the left, but not the right, hand. (E) Severity of motor neglect is significantly associated (z >4.49) with damage at several discrete areas within the right hemisphere (including white matter near the putamen, inferior frontal gyrus, rolandic operculum and parietal supramarginal gyrus). RT, reaction time; SOA, stimulus onset asynchrony.
© Copyright Policy - openaccess
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2602747&req=5

JNN-79-12-1401-f01: Paradigm, behavioural and lesion data. Subjects performed a masked prime task (A). Arrow stimuli subtended approximately 1.5×1°. Neutral primes comprised the arrows rearranged forming a square that carried no directional information (not shown). Twelve blocks of 24 stimuli contained six different trial types randomised with the constraint that each condition occurred the same number of times per block. Hands were covered during the experiment to prevent visual guidance of movement. Subjects were instructed to fixate the laptop display centrally and eye position was monitored by the experimenter. A practice session (<2 min) took place beforehand. Only patients with motor neglect showed significant reaction time delay when a right prime preceded a movement with the left hand (B, red circle). Hence right hand motor plans significantly intrude on left hand movement, but not vice versa, only in patients with motor neglect. Lesions were plotted using MRICro software (www.mricro.com) from either CT or MR. Lesion subtraction (patients with motor neglect minus those without) shows frontal white matter selectively affected in patients with motor neglect (C). (D) Brunner–Munzel statistic revealed that right putamen and subcortical white matter were significantly associated (z scores >4.47) with abnormal performance in the masked prime task using the left, but not the right, hand. (E) Severity of motor neglect is significantly associated (z >4.49) with damage at several discrete areas within the right hemisphere (including white matter near the putamen, inferior frontal gyrus, rolandic operculum and parietal supramarginal gyrus). RT, reaction time; SOA, stimulus onset asynchrony.
Mentions: Here we probe the inhibitory processes involved in motor neglect behaviourally using a masked prime task which offers an important window onto automatic inhibitory control.6 This paradigm has recently been deployed to probe deficits in Parkinson’s disease as well as focal lesions of supplementary motor areas.7 8 In this task, prime arrow stimuli are presented for less than 50 ms and then masked (fig 1A). Normal observers are not able to report having seen the prime. However, the prime influences performance when a subsequent target arrow requires a response.

Bottom Line: Using a masked prime task, it was shown that when patients with left motor neglect plan to move their left hand, irrelevant right limb motor programmes intrude, causing delay.Lesion analysis reveals that such asymmetry of motor programming occurs after infarcts of the right putamen and motor association areas.This demonstration of failure to inhibit ipsilesional limb motor plans suggests potential benefit from interventions that might act to restore balance in action planning.

View Article: PubMed Central - PubMed

Affiliation: Institute of Neurology and National Hospital for Neurology and Neurosurgery, 17 Queen Square, London WC1N3AR, UK. l.coulthard@ion.ucl.ac.uk

ABSTRACT
Motor neglect, underuse of one side of the body not explained by weakness or sensory impairment, is a common consequence of stroke that is surprisingly little understood. Behavioural and neuroanatomical hallmarks of the disorder are investigated. Using a masked prime task, it was shown that when patients with left motor neglect plan to move their left hand, irrelevant right limb motor programmes intrude, causing delay. Lesion analysis reveals that such asymmetry of motor programming occurs after infarcts of the right putamen and motor association areas. This demonstration of failure to inhibit ipsilesional limb motor plans suggests potential benefit from interventions that might act to restore balance in action planning.

Show MeSH
Related in: MedlinePlus