TY - JOUR
T1 - Acquisition of a simple motor skill
T2 - task-dependent adaptation and long-term changes in the human soleus stretch reflex
AU - Mrachacz-Kersting, Natalie
AU - Kersting, Uwe Gustav
AU - de Brito Silva, Priscila
AU - Makihara, Yukiko
AU - Arendt-Nielsen, Lars
AU - Sinkjaer, Thomas
AU - Thompson, Aiko K
PY - 2019/7
Y1 - 2019/7
N2 - Changing the H reflex through operant conditioning leads to CNS multisite plasticity and can affect previously learned skills. To further understand the mechanisms of this plasticity, we operantly conditioned the initial component (M1) of the soleus stretch reflex. Unlike the H reflex, the stretch reflex is affected by fusimotor control, comprises several bursts of activity resulting from temporally dispersed afferent inputs, and may activate spinal motoneurons via several different spinal and supraspinal pathways. Neurologically normal participants completed 6 baseline sessions and 24 operant conditioning sessions in which they were encouraged to increase (M1up) or decrease (M1down) M1 size. Five of eight M1up participants significantly increased M1; the final M1 size of those five participants was 143 ± 15% (mean ± SE) of the baseline value. All eight M1down participants significantly decreased M1; their final M1 size was 62 ± 6% of baseline. Similar to the previous H-reflex conditioning studies, conditioned reflex change consisted of within-session taskdependent adaptation and across-session long-term change. Taskdependent adaptation was evident in conditioning session 1 with M1up and by session 4 with M1down. Long-term change was evident by session 10 with M1up and by session 16 with M1down. Taskdependent adaptation was greater with M1up than with the previous H-reflex upconditioning. This may reflect adaptive changes in muscle spindle sensitivity, which affects the stretch reflex but not the H reflex. Because the stretch reflex is related to motor function more directly than the H reflex, M1 conditioning may provide a valuable tool for exploring the functional impact of reflex conditioning and its potential therapeutic applications. NEW & NOTEWORTHY Since the activity of stretch reflex pathways contributes to locomotion, changing it through training may improve locomotor rehabilitation in people with CNS disorders. Here we show for the first time that people can change the size of the soleus spinal stretch reflex through operant conditioning. Conditioned stretch reflex change is the sum of task-dependent adaptation and long-term change, consistent with H-reflex conditioning yet different from it in the composition and amount of the two components.
AB - Changing the H reflex through operant conditioning leads to CNS multisite plasticity and can affect previously learned skills. To further understand the mechanisms of this plasticity, we operantly conditioned the initial component (M1) of the soleus stretch reflex. Unlike the H reflex, the stretch reflex is affected by fusimotor control, comprises several bursts of activity resulting from temporally dispersed afferent inputs, and may activate spinal motoneurons via several different spinal and supraspinal pathways. Neurologically normal participants completed 6 baseline sessions and 24 operant conditioning sessions in which they were encouraged to increase (M1up) or decrease (M1down) M1 size. Five of eight M1up participants significantly increased M1; the final M1 size of those five participants was 143 ± 15% (mean ± SE) of the baseline value. All eight M1down participants significantly decreased M1; their final M1 size was 62 ± 6% of baseline. Similar to the previous H-reflex conditioning studies, conditioned reflex change consisted of within-session taskdependent adaptation and across-session long-term change. Taskdependent adaptation was evident in conditioning session 1 with M1up and by session 4 with M1down. Long-term change was evident by session 10 with M1up and by session 16 with M1down. Taskdependent adaptation was greater with M1up than with the previous H-reflex upconditioning. This may reflect adaptive changes in muscle spindle sensitivity, which affects the stretch reflex but not the H reflex. Because the stretch reflex is related to motor function more directly than the H reflex, M1 conditioning may provide a valuable tool for exploring the functional impact of reflex conditioning and its potential therapeutic applications. NEW & NOTEWORTHY Since the activity of stretch reflex pathways contributes to locomotion, changing it through training may improve locomotor rehabilitation in people with CNS disorders. Here we show for the first time that people can change the size of the soleus spinal stretch reflex through operant conditioning. Conditioned stretch reflex change is the sum of task-dependent adaptation and long-term change, consistent with H-reflex conditioning yet different from it in the composition and amount of the two components.
KW - Humans
KW - Operant conditioning
KW - Plasticity
KW - Stretch reflex
KW - Adaptation, Physiological
KW - Adult
KW - Female
KW - Humans
KW - Male
KW - Motor Skills
KW - Muscle, Skeletal/innervation
KW - Reflex, Stretch
UR - https://www.mendeley.com/catalogue/84a151b2-0eff-3be0-96f2-bfe16f1ec8ab/
U2 - 10.1152/jn.00211.2019
DO - 10.1152/jn.00211.2019
M3 - Journal articles
C2 - 31166816
SN - 0022-3077
VL - 122
SP - 435
EP - 446
JO - Journal of neurophysiology
JF - Journal of neurophysiology
IS - 1
ER -