Lack of interlimb transfer following visuomotor adaptation in a person with CMG
Mentor 1
Jinsung Wang
Start Date
1-5-2020 12:00 AM
Description
Congenital mirror movements (CMMs) have been conventionally thought to occur due to the corticospinal tracts that project irregularly to both sides of the body. More recently, it has been suggested that both brain hemispheres are activated during anticipated unilateral movements due to deficient transcallosal inhibition, leading to mirror movements on the unintended side as well. To further understand the mechanisms underlying CMMs, we examined the pattern of interlimb transfer following visuomotor adaptation in ‘DB’, an individual with CMMs. DB’s CMMs were established by detecting EMG signals in both arms during intended unilateral movements, and also when transcranial magnetic stimulation (TMS) was applied to the motor cortex. Following that, DB performed reaching movements with the left arm under a visuomotor condition in which the visual display was rotated 30 counterclockwise about the start circle, and then with the right arm under the same (experiment 1) or opposing (experiment 2) rotation condition. DB’s performances were compared with the data from control subjects. In both experiments, DB was able to adapt to the rotation with either arm; however, movement errors at the beginning of right-arm adaptation did not differ from those at the beginning of left-arm adaptation, indicating no transfer. These transfer patterns differ from those observed in controls, who demonstrated substantial transfer when the rotation directions were the same between the arms, but no transfer when they were opposite. These findings suggest that in DB, both hemispheres are activated during unilateral movements, but interhemispheric communication is compromised, resulting in mirror movements on the involuntary side.
Lack of interlimb transfer following visuomotor adaptation in a person with CMG
Congenital mirror movements (CMMs) have been conventionally thought to occur due to the corticospinal tracts that project irregularly to both sides of the body. More recently, it has been suggested that both brain hemispheres are activated during anticipated unilateral movements due to deficient transcallosal inhibition, leading to mirror movements on the unintended side as well. To further understand the mechanisms underlying CMMs, we examined the pattern of interlimb transfer following visuomotor adaptation in ‘DB’, an individual with CMMs. DB’s CMMs were established by detecting EMG signals in both arms during intended unilateral movements, and also when transcranial magnetic stimulation (TMS) was applied to the motor cortex. Following that, DB performed reaching movements with the left arm under a visuomotor condition in which the visual display was rotated 30 counterclockwise about the start circle, and then with the right arm under the same (experiment 1) or opposing (experiment 2) rotation condition. DB’s performances were compared with the data from control subjects. In both experiments, DB was able to adapt to the rotation with either arm; however, movement errors at the beginning of right-arm adaptation did not differ from those at the beginning of left-arm adaptation, indicating no transfer. These transfer patterns differ from those observed in controls, who demonstrated substantial transfer when the rotation directions were the same between the arms, but no transfer when they were opposite. These findings suggest that in DB, both hemispheres are activated during unilateral movements, but interhemispheric communication is compromised, resulting in mirror movements on the involuntary side.
