Effects of Unilateral Motor Cortex Lesion on Ipsilesional Hand's Reach and Grasp Performance in Monkeys: Relationship With Recovery in the Contralesional Hand

Abstract

Manual dexterity, a prerogative of primates, is under the control of the corticospinal (CS) tract. Because 90-95% of CS axons decussate, it is assumed that this control is exerted essentially on the contralateral hand. Consistently, unilateral lesion of the hand representation in the motor cortex is followed by a complete loss of dexterity of the contralesional hand. During the months following lesion, spontaneous recovery of manual dexterity takes place to a highly variable extent across subjects, although largely incomplete. In the present study, we tested the hypothesis that after a significant postlesion period, manual performance in the ipsilesional hand is correlated with the extent of functional recovery in the contralesional hand. To this aim, ten adult macaque monkeys were subjected to permanent unilateral motor cortex lesion. Monkeys' manual performance was assessed for each hand during several months postlesion, using our standard behavioral test (modified Brinkman board task) that provides a quantitative measure of reach and grasp ability. The ipsilesional hand's performance was found to be significantly enhanced over the long term (100-300 days postlesion) in six of ten monkeys, with the six exhibiting the best, though incomplete, recovery of the contralesional hand. There was a statistically significant correlation (r = 0.932; P < 0.001) between performance in the ipsilesional hand after significant postlesion period and the extent of recovery of the contralesional hand. This observation is interpreted in terms of different possible mechanisms of recovery, dependent on the recruitment of motor areas in the lesioned and/or intact hemispheres.

Representation of motor habit in a sequence of repetitive reach and grasp movements performed by macaque monkeys: Evidence for a contribution of the dorsolateral prefrontal cortex

“…Furthermore, for the largest unilateral lesion of dlPFC (Mk-AV), the change of motor habits affected both hand, whereas in the case of a smaller dlPFC lesion (Mk-JO) the change was observed for the contralesional hand only. The change of motor habit related to dlPFC lesion was not just transient but lasted for at least 2e3 weeks (the evolution on the longer long-term is unknown, as the monkeys involved in our protocol were then subjected to a lesion of the primary motor cortex; see Kaeser et al, 2010Kaeser et al, , 2011. To the best of our knowledge, the present study represents a first evidence for a role of dlPFC in motor habits, such as motor sequencing on a "free-will" basis.…”

“…The monkeys ranged from 2.5 to 5.5 years old at the time of initiation of behavioural training sessions. All the behavioural and surgical procedures were approved by the local ethical committee, in accordance with the Guidelines for the Care and Use of Laboratory Animals and approved by Swiss veterinary authorities (see e.g., Kaeser et al, 2010Kaeser et al, , 2011Bashir et al, 2012;Schmidlin et al, 2011). Briefly, the monkeys were trained to enter and sit into a Plexiglas primate chair (Schmidlin et al, 2011).…”

“…For the present investigation, the motor performances at the modified Brinkman board task e static e and the rotating Brinkman board task e moving either clockwise or counterclockwise e were analysed. These two tasks were described in more detail in previous studies (Brinkman and Kuypers, 1973;Brinkman, 1984;Liu and Rouiller, 1999;Freund et al, 2009;Kaeser et al, 2010Kaeser et al, , 2011Schmidlin et al, 2011) and can be seen on the following web page: http://www.unifr.ch/neuro/rouiller/ research/brink.php. For each monkey, the performance of the left hand and the right hand were analysed separately.…”

“…The surgical procedures were described in previous reports from this laboratory (Liu and Rouiller, 1999;Kaeser et al, 2010Kaeser et al, , 2011Bashir et al, 2012). Briefly, after completion of training and once the monkey reached a behavioural plateau, the animal was subjected to the following surgical procedures.…”

“…Once the entire experiment was completed (effect of subsequent motor cortex lesion and recovery, see Bashir et al, 2012;Kaeser et al, 2010Kaeser et al, , 2011, the monkeys were sacrificed. They were first anesthetized with an intramuscular ketamine injection, and then received a lethal dose of sodium pentobarbital (90 mg/kg).…”