Motor learning transiently changes cortical somatotopy.
Learning a complex motor skill is associated with changes in motor cortex representations of trained body parts. It has been suggested that representation changes reflect the storage of a skill, i.e., the motor memory trace. If a reflection of the trace, such modifications should persist after training is stopped for as long as the skill is retained. The objective here was to test the persistence of learning-related changes in the representation of the forelimb of the rat after learning a reaching task using repeated epidural stimulation mapping of primary motor cortex. It is shown that the forelimb representations enlarge after 8 days of training (n=8) but contract while performing arm movements without learning (n=7, p=0.006); hindlimb representations remain unchanged. Enlargement correlated with learning success (r=0.82; p=0.012). Subsequently, after 8 days without training, representation size reverted to baseline while the motor skill was retained. Somatotopy remained unaltered by a second training phase in which performance did not improve further (n=5). These findings suggest that successful acquisition but not storage of a motor skill depends on cortical map changes. The motor memory trace in rats may require changes in motor cortex organization other than those detected by stimulation mapping.
Molina-Luna
Katiuska
K
Department of General Neurology, Hertie Institute for Clinical Brain Research, University of Tübingen, Hoppe-Seyler-Str. 3, 72076 Tübingen, Germany.
Hertler
Benjamin
B
Buitrago
Manuel M
MM
Luft
Andreas R
AR
D000818:Animals; D001931:Brain Mapping; D002540:Cerebral Cortex / Q000502:physiology*; D003627:Data Interpretation, Statistical; D004824:Epidural Space / Q000502:physiology; D005552:Forelimb / Q000098:blood supply / Q000294:innervation; D007858:Learning / Q000502:physiology*; D016014:Linear Models; D009044:Motor Cortex / Q000502:physiology; D009048:Motor Skills / Q000502:physiology*; D011597:Psychomotor Performance / Q000502:physiology; D051381:Rats; D020318:Rats, Long-Evans; D012039:Regional Blood Flow / Q000502:physiology