![]() ![]() The classical perturbation methods used in these studies lack temporal specificity and allow for the emergence of compensatory mechanisms (but see supplement of Peters et al., 2014). Previous inactivation experiments have suggested the cortex tunes-rather than initiates and executes-motor programs to achieve dexterous movement ( Walker and Fulton, 1938 Lawrence and Kuypers, 1968 Castro, 1972 Passingham et al., 1983 Martin and Ghez, 1991 Whishaw, 2000 Fogassi et al., 2001 Peters et al., 2014). Cortical neurons display dynamic activity patterns during movement planning and execution, but their functional contribution to skilled action cannot be assessed from recordings alone ( Lemon, 1993 Scott, 2003 Evarts, 2011). Neurophysiological recordings, inactivation experiments, and stimulation studies have been used to describe the role of cortex in motor control. Motor control is achieved by the coordinated activity of myriad neural structures, including the cerebral cortex, basal ganglia, cerebellum, and spinal cord. Future studies could also investigate how learning a set of movements affects the structure of cortical neurons and their connections, thus suggesting how these memories are stored.Įxecution of complex voluntary movements depends on many functions including choosing a behavior, specifying each step, enacting the movements, and learning to perform with increasing skill. Overall, Guo et al.’s work opens the question of how the instructions that describe the learned movement are encoded within the motor cortex and its downstream networks. This was particularly likely to occur if the animal had been deprived of food before the test or was particularly well trained, but did not depend on the position of the limb. This implies that the cortical activity evoked at the end of inactivation acts to trigger the full movement sequence. Unexpectedly, even during rest periods when there was no food pellet and the mice were just waiting for the experiment to begin, turning the motor cortex off and then back on again suddenly caused the mice to perform the complete grabbing motion. ![]() When the cortex was reactivated, the mice instantly resumed trying to pick up the food pellet. However, only the learned, skilled task was frozen by motor cortex shutdown mice could still move their limbs normally if the motor cortex was instead shut down during routine movements. Suddenly shutting down the motor cortex at the start of a trial prevented the mice from starting the task, and shut down part way through the task caused the front limbs of the mice to freeze in midair. have now used optogenetics to control the motor cortex as the mice performed a task they had been trained to do – reaching for and picking up a food pellet. ![]() By genetically modifying animals to produce light-sensitive channel proteins in certain brain cells, the activity of particular regions of the brain can be controlled by shining light onto them. ![]() Part of the brain called the motor cortex is thought to be important for learning and controlling these skilled movements, but its exact role in these processes is not clear.Ī technique called optogenetics allows the roles of individual parts of the brain to be studied by rapidly altering their activity, whilst minimizing the likelihood that the brain will compensate for these changes. For example, picking up an object involves several steps that must be precisely controlled, including reaching towards the item and holding it using the right amount of pressure to not crush it or drop it. Many of the movements that humans and other animals make every day are deceptively complex and only appear easy because of extensive practice. ![]()
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