How do we adapt our movements and learn new skills?

First, try out the interactive motor learning demos

For background information, see how does the brain process information? and how does the brain control movement?.

In “The Office”, Dwight complained that he hit himself in the head with his office phone one day. It turns out that Jim had been gradually placing coins in the handset of the phone, making it heavier. Dwight adapted his movements by using more force to pick up the phone. When Jim removed all the coins, Dwight used too much force. This is an example of motor adaptation, a form of learning that allows us to make adjustments to our movements when the environment changes. When we aren’t being pranked, motor adaptation is usually very helpful. If you are playing tennis and the direction of the wind changes, you must adapt your shots in order to keep them accurate. In addition to adapting and adjusting our movements, the brain learns to produce entirely new motor skills that can last a lifetime, like learning to walk, ride a bike, or play a sport.

Learning changes the connections between brain cells

Not all forms of learning rely on the same system in the brain. In 1953 in Hartford Connecticut, Henry Molaison had most of the medial temporal lobes of his brain removed in an experimental surgery to treat his severe epilepsy. Although the surgery was successful in treating Molaison’s epilepsy, he became famous in neuroscience research as “Patient H.M.” due to the amnesia he experienced.

We now know that the medial temporal lobes are important for learning and memory, as H.M. lost the ability to remember any new facts or events for more than a matter of minutes. However, H.M. could still learn and retain motor skills. In one experiment, he practiced tracing shapes on a piece of paper while he could only see what he was doing in a mirror. This task is essentially the same as the task in demo #3, where the direction of cursor movement was reversed, or mirrored (Try out the motor learning demos here). H.M. improved with practice and was able to retain this skill over the course of three days, although he did not recall having done the task before. This finding demonstrated that memories for motor skills depend on different brain structures than memories for facts and events¹.

Unsurprisingly, motor learning creates memories that are stored in the brain areas involved in controlling movements. Many studies have scanned peoples’ brains during motor learning or before and after extensive practice of a motor skill. Changes related to learning have been observed in motor areas including the cerebellum, basal ganglia, and motor cortex^2,3. Learning also involves changes in parts of the cerebral cortex involved in processing sensory information that helps to guide our movements⁴.

The cerebellum is important for learning from errors

Another way that scientists understand the role of different brain areas in motor learning is by studying people with neurological disorders that affect specific parts of the brain. People with disorders that affect the cerebellum are drastically impaired in learning during the kinds of tasks that you performed in the interactive demos^5-7. The cerebellum is important for adapting our movements to correct errors, such as when the cursor moved in an unusual direction during the demos or when the wind causes your tennis serve to go off course.

The basal ganglia are important for retention and new skills

The cerebellum allows us to make quick adjustments in response to errors, but learning new motor skills and retaining motor learning for days or even decades seems to also depend on the basal ganglia. Parkinson’s disease and Huntington’s disease are both neurological illnesses that affect the basal ganglia. People with these disorders show relatively normal learning during the kinds of tasks in demo #1 and demo #2^8-10, but one study showed that these patients could not learn in a task similar to demo #3¹¹. Demos #1 and #2 involve learning to adapt movements to correct errors, while demo #3 involves learning a new motor skill from scratch^12,13. These results suggest that the basal ganglia are important for learning new motor skills. People with basal ganglia disorders can still adapt their existing motor skills to correct errors because these disorders do not directly affect the cerebellum. However, they may have difficulties retaining this learning over time^8-10.

Motor learning changes the motor cortex

The role of the motor cortex in motor adaptation has been studied using non-invasive brain stimulation in healthy research participants. Transcranial magnetic stimulation (TMS) can be used to focus a powerful magnetic field over the motor cortex, which causes electrical currents in the brain. If this stimulation is focused on a particular part of the body map in the motor cortex, it causes the muscles in the corresponding part of the body to twitch. In a very simple way, this is a form of brain control! After practicing a motor skill, the twitches caused by TMS become larger in the body part that was used for the skill^14-16. This indicates that motor learning involves changes that allow the cells in the motor cortex to become excited more easily. Studies have also shown that learning a motor skill can expand the area of the motor cortex that maps onto the body parts involved in the skill.

Transcranial magnetic stimulation (TMS) can be used to stimulate the motor cortex non-invasively. Figure created with BioRender.com.

References

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2. Hardwick, R. M., Rottschy, C., Miall, R. C. & Eickhoff, S. B. A quantitative meta-analysis and review of motor learning in the human brain. Neuroimage 67, 283–297 (2013).
3. Lohse, K. R., Wadden, K., Boyd, L. A. & Hodges, N. J. Motor skill acquisition across short and long time scales: a meta-analysis of neuroimaging data. Neuropsychologia 59, 130–141 (2014).
4. Ostry, D. J. & Gribble, P. L. Sensory Plasticity in Human Motor Learning. Trends Neurosci. 39, 114–123 (2016).
5. Taylor, J. A., Klemfuss, N. M. & Ivry, R. B. An explicit strategy prevails when the cerebellum fails to compute movement errors. Cerebellum 9, 580–586 (2010).
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10. Marinelli, L. et al. Learning and consolidation of visuo-motor adaptation in Parkinson’s disease. Parkinsonism Relat. Disord. 15, 6–11 (2009).
11. Gutierrez-Garralda, J. M. et al. The effect of Parkinson’s disease and Huntington’s disease on human visuomotor learning. Eur. J. Neurosci. 38, 2933–2940 (2013).
12. Telgen, S., Parvin, D. & Diedrichsen, J. Mirror Reversal and Visual Rotation Are Learned and Consolidated via Separate Mechanisms: Recalibrating or Learning De Novo? J. Neurosci. 34, 13768–13779 (2014).
13. Yang, C. S., Cowan, N. J. & Haith, A. M. De novo learning versus adaptation of continuous control in a manual tracking task. bioRxiv 2020.01.15.906545 (2021) doi:10.1101/2020.01.15.906545.
14. Pascual-Leone, A. et al. Modulation of muscle responses evoked by transcranial magnetic stimulation during the acquisition of new fine motor skills. J. Neurophysiol. 74, 1037–1045 (1995).
15. Orban de Xivry, J.-J., Ahmadi-Pajouh, M. A., Harran, M. D., Salimpour, Y. & Shadmehr, R. Changes in corticospinal excitability during reach adaptation in force fields. J. Neurophysiol. 109, 124–136 (2013).
16. Christiansen, L. et al. Progressive practice promotes motor learning and repeated transient increases in corticospinal excitability across multiple days. Brain Stimul. 11, 346–357 (2018).