Scientists identified a disinhibitory circuit in the cerebellum that helps explain how learning from experience refines movements such as walking or reaching. The study, led by Court Hull and Wade G. Regehr with first author Fernando Santos Valencia, was published in Nature and involved researchers at Duke and Harvard Medical School.
Climbing fibers send strong error signals when a movement goes wrong. They activate Purkinje cells and trigger bursts of calcium that support synaptic plasticity. The puzzle was that climbing fibers also activate inhibitory cells that should prevent those calcium signals. Using high-resolution electron microscopy, brain slice experiments, and recordings in living mice, the team investigated this paradox.
They found climbing fibers preferentially target ML12 inhibitory cells. ML12 cells do not inhibit Purkinje cells directly; instead they suppress ML11 cells, which normally reduce learning. When many climbing fibers fire together—often during clear sensory events like tripping or a loud sound—inhibition falls and Purkinje cells produce larger calcium signals that reshape connections. The authors say this braking mechanism helps open and close windows for plasticity and may be relevant to motor disorders such as ataxias and to conditions linked to cerebellar dysfunction.
Difficult words
- cerebellum — part of the brain that controls movement
- circuit — a connected group of brain cells
- disinhibitory — reducing inhibition to increase activity
- climbing fiber — nerve fibers that send error signalsclimbing fibers
- synaptic plasticity — ability of connections between cells to change
- inhibition — process that reduces activity of other cells
- ataxia — a movement disorder causing unsteady movementsataxias
- calcium — a chemical element important for cell signals
Tip: hover, focus or tap highlighted words in the article to see quick definitions while you read or listen.
Discussion questions
- How might opening and closing windows for plasticity help a person learn a new movement?
- Can you give an example of a clear sensory event that might cause many climbing fibers to fire together?
- Why could understanding this cerebellar circuit be important for treating movement disorders?
Related articles
Targeting a brain circuit to reduce opioid relapse
Researchers at Washington State University found that lowering activity in a specific brain connection cut heroin-seeking in a preclinical model. The study identifies a pathway between the prelimbic cortex and the paraventricular thalamus and tests two ways to reduce its activity.
Navigation brain cells in retrosplenial cortex preserved across evolution
Researchers found two special neuron types in the retrosplenial cortex that help navigation. These cells are conserved between mice and rats, linked to spatial disorientation in Alzheimer’s, and are now being studied in humans.
Dopamine helps lock in new skills during sleep
A study from the University of Michigan finds that dopamine neurons become active during NREM sleep soon after a person learns a movement. Their activity, together with sleep spindles, strengthens motor memories and improves skills after sleep.
Sensory Brain Areas Support Speech Memory
A study tested which brain systems keep newly learned speech movements. Disrupting sensory brain areas (auditory or somatosensory) reduced memory for the new speech, while disrupting the motor area did not. The finding may help speech rehabilitation.