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Brain Stimulation Reduces Competition Between Memories

Wednesday, July 13th, 2011

Transcranial magnetic stimulation (TMS) is able to minimize forgetfulness by disrupting targeted brain regions as they compete between memories, according to a new study at Beth Israel Deaconess Medical Center.

“For the last 100 years, it has been appreciated that trying to learn facts and skills in quick succession can be a frustrating exercise,” explains Edwin Robertson, MD, DPhil, an Associate Professor of Neurology at Harvard Medical School. “Because no sooner has a new memory been acquired than its retention is jeopardized by learning another fact or skill.”

Robertson, along with neurologist and co-author Daniel Cohen, MD, observed 120 college-age students who participated in two memory tests.

The first was a finger-tapping motor skills task, and the second was a memory test in which volunteers had to remember a series of words. Half of the participants performed the tasks in this order, while the other half learned these same two tasks in reverse order.

“The study subjects performed these back-to-back exercises in the morning,” he explains. “They then returned 12 hours later and re-performed the tests. As predicted, their recall for either the word list or the motor-skill task had decreased when they were re-tested.”

Just after the initial testing, the researchers administered TMS which is a noninvasive procedure that uses a magnetic simulator that can create a current in the brain through a magnetic field.

“Because brain cells communicate through a process of chemical and electrical signals, applying a mild electrical current to the brain can influence the signals,” Robertson explains.

The researchers focused on two specific brain areas: the dorsolateral prefrontal cortex and the primary motor cortex. They found that when they applied TMS to these specific regions, they could diminish the interference and competition between the motor skill and word tasks and both memories remained intact.

“This elegant study provides fundamental new insights into the way our brain copes with the challenge of learning multiple skills and making multiple memories,” says Alvaro Pascual-Leone, MD, PhD, Director of the Berenson-Allen Center for Noninvasive Brain Stimulation.

“Specific brain structures seem to carefully balance how much we retain and how much we forget. Learning and remembering is a dynamic process and our brain devotes resources to keep the process flexible. By better understanding this process, we may be able to find novel approaches to help enhance learning and treat patients with memory problems and learning disabilities.”

“Our observations suggest that distinct mechanisms support the communication between different types of memory processing,” adds Robertson.

“This provides a more dynamic and flexible account of memory organization than was previously believed. We’ve demonstrated that the interference between memories is actively mediated by brain areas and so may serve an important function that has previously been overlooked.”

The findings are described in the June 26 Advance Online issue of Nature Neuroscience.

Tags: learning, memories, memory, neuropsychiatry, psychiatrist, psychiatry, tms, transcranial magnetic stimulation
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