Cerebellum Only Necessary for Some Muscle Memory, Harvard Researchers Find

In an August study, researchers at the Harvard School of Engineering and Applied Sciences identified a new distinction between long- and short-term motor memories — a class of memories developed through repeated physical movements.

The study, published in the Proceedings of the National Academy of Sciences, suggested that the cerebellum is necessary for the formation of new long-term, but not short-term, motor memories.

Beginning last fall, researchers re-analyzed raw data from two previous studies — conducted in 2010 and 2013 — assessing motor learning in people with severe cerebellar ataxia, a condition that disrupts physical coordination in patients. Their analysis indicated that without proper cerebellum function, patients were unable to form long term memories in a series of disc-throwing trials.

Maurice A. Smith, a Harvard bioengineering professor and co-author on the study, said the lab has long been studying the distinction between long- and short-term motor memories.

Smith said the “discoordination” seen in patients of cerebellar ataxia proved that longer- and shorter-term motor memories require separate processes of formation.

“We knew that if there was a dichotomy between the really short term — called fast learning — and longer term slow learning, that it would be that they have some problem with the longer term slow learning,” Smith said.

“We just wondered if the cerebellum actually could dissociate them,” he added.

Still, Smith said that the researchers’ August findings leave room for further research. In the study, the difference between long and short term memory formation was only the difference between “a few seconds” and “a few minutes,” per Smith, though he said contradictory results for long-term memory are unlikely.

“If memory can’t survive one or two minutes, it’s hard to imagine it survives hours or days,” Smith said.

According to Smith, patients with cerebellar ataxia often face societal obstacles as a result of their inability to establish longer-term muscle memory.

“Unfortunately, someone with mild or moderate cerebellar ataxia who’s still functional and can drive, they get pulled over by the police. They often get taken in for drunk driving,” Smith said. “It’s because they’re asked to get out of the car and walk, and they look like they’re someone drunk.”

Harvard psychology professor Daniel L. Schacter, who was not involved in the research, said the data was “very thoroughly analyzed.” In future testing, he said, researchers should attempt to generalize the findings among a broader range of motor tasks.

“They make a convincing case that there is a distinction here,” Schacter said.