TY - JOUR
T1 - Altering effort costs in Parkinson’s disease with noninvasive cortical stimulation
AU - Salimpour, Yousef
AU - Mari, Zoltan K.
AU - Shadmehr, Reza
N1 - Publisher Copyright:
© 2015 the authors.
PY - 2015/9/2
Y1 - 2015/9/2
N2 - In Parkinson’s disease (PD), the human brain is capable of producing motor commands, but appears to require greater than normal subjective effort, particularly for the more-affected side. What is the nature of this subjective effort and can it be altered? We used an isometric task in which patients produced a goal force by engaging both arms, but were free to assign any fraction of that force to each arm. The patients preferred their less-affected arm, but only in some directions. This preference was correlated with lateralization of signaldependent noise: the direction of force for which the brain was less willing to assign effort to an arm was generally the direction for which that arm exhibited greater noise. Therefore, the direction-dependent noise in each arm acted as an implicit cost that discouraged use of that arm. To check for a causal relationship between noise and motor cost, we used bilateral transcranial direct current stimulation of the motor cortex, placing the cathode on the more-affected side and the anode on the less-affected side. This stimulation not only reduced the noise on the more-affected arm, it also increased the willingness of the patients to assign force to that arm. Ina3ddouble-blind study and in a 10 d repeated stimulation study, bilateral stimulation of the two motor cortices with cathode on the more-affected side reduced noise and increased the willingness of the patients to exert effort. This stimulation also improved the clinical motor symptoms of the disease.
AB - In Parkinson’s disease (PD), the human brain is capable of producing motor commands, but appears to require greater than normal subjective effort, particularly for the more-affected side. What is the nature of this subjective effort and can it be altered? We used an isometric task in which patients produced a goal force by engaging both arms, but were free to assign any fraction of that force to each arm. The patients preferred their less-affected arm, but only in some directions. This preference was correlated with lateralization of signaldependent noise: the direction of force for which the brain was less willing to assign effort to an arm was generally the direction for which that arm exhibited greater noise. Therefore, the direction-dependent noise in each arm acted as an implicit cost that discouraged use of that arm. To check for a causal relationship between noise and motor cost, we used bilateral transcranial direct current stimulation of the motor cortex, placing the cathode on the more-affected side and the anode on the less-affected side. This stimulation not only reduced the noise on the more-affected arm, it also increased the willingness of the patients to assign force to that arm. Ina3ddouble-blind study and in a 10 d repeated stimulation study, bilateral stimulation of the two motor cortices with cathode on the more-affected side reduced noise and increased the willingness of the patients to exert effort. This stimulation also improved the clinical motor symptoms of the disease.
KW - Motor costs
KW - Parkinson’s disease
KW - Signal-dependent noise
KW - TDCS
UR - http://www.scopus.com/inward/record.url?scp=84940945815&partnerID=8YFLogxK
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U2 - 10.1523/JNEUROSCI.1827-15.2015
DO - 10.1523/JNEUROSCI.1827-15.2015
M3 - Article
C2 - 26338339
AN - SCOPUS:84940945815
SN - 0270-6474
VL - 35
SP - 12287
EP - 12302
JO - Journal of Neuroscience
JF - Journal of Neuroscience
IS - 35
ER -