Brain Stimulation Preserves a Memory When Other Memories Clash

As a student, I have often had problems studying for multiple examinations, when I had to remember two different sets of facts one after the another. Whenever I studied for Geography, I often forgot some recent answers I had memorized for Physics. It's been widely believed that this interference between memories develops because the brain simply doesn't have the necessary capacity to process both memories in quick succession. But this belief may not be true.

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Map your Memory

A recent study by researchers at Beth Israel Deaconess Medical Center (BIDMC) suggests that specific brain areas actively organize competition between memories, and that by cutting off targeted brain areas through Trans-cranial Magnetic Stimulation (TMS), you can conserve memory, and prevent forgetting.

Edwin Robertson, MD, DPhil, an Associate Professor of Neurology at Harvard Medical School and BIDMC," For the last 100 years, it has been appreciated that trying to learn facts and skills in quick succession can be a frustrating exercise. Because no sooner has a new memory been acquired than its retention is jeopardized by learning another fact or skill." Robertson, along with BIDMC neurologist and co-author Daniel Cohen, MD, studied a group of 120 college-age students who executed two simultaneous memory tests. The first involved a finger-tapping motor skills task, whereas the second was a declarative memory task in which participants memorized a series of words. (Half of the group performed the tasks in this order, while a second group 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."

In the latter part of the study, Robertson and Cohen employed TMS following the initial testing. TMS is a non-invasive technique that applies a magnetic simulator to generate a magnetic field that can create a flow of current in the brain. "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. In this particular case, the researchers targeted two specific brain regions, the dorsolateral prefrontal cortex and the primary motor cortex. They discovered that by applying TMS to specific brain areas, they were able to reduce the interference and rivalry between the motor skill and word-list tasks and both memories remained undamaged in any way.

This refined study provides fundamental new insights in developing multiple memories. Specific brain structures seem to carefully balance how much we retain and how much we forget. This method once understood properly, can be employed to find novel approaches and treat patients with learning disabilities and poor memory. Robertson adds,"Our observations suggest that distinct mechanisms support the communication between different types of memory processing. 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."

This study was backed up in terms of grants by the National Institutes of Health (NIH) and the National Science Foundation.

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