How sleep helps the brain learn specific tasks

Teresa Tanoos's picture
Researchers uncover secrets to sleep effect on motor tasks
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It’s long been known that sleep helps our brains incorporate what we’ve learned during waking hours, but scientists have historically struggled to figure out precisely how the brain works to make that happen.

Now, however, researchers have located the brainwave frequencies and the region of the brain associated with sleep-enhanced learning of certain motor tasks, such as typing or playing piano.

In a “first of its kind” study published in the Journal of Neuroscience, researchers utilized three different brain scans to identify changes in specific brainwaves and the exact location in the brain where such changes occurred while learning certain tasks.

The study involved 15 volunteers who participated in various motor learning experiments featuring a series of finger-tapping tasks.

During the first three nights of experiments, the participants slept at whatever time they wished. Their brains were then scanned using magnetoencephalography (MEG) to measure rhythmic neural activity in the central nervous system, as well as polysomnography (PSG), to keep track of the sleep phase.

By the end of the three nights, the participants became accustomed to sleeping in their surroundings, and the researchers reported good baseline measurements of brain activity.

The participants were then required to carry out a series of finger-tapping tasks on their "non-dominant" hand in an effort to make the task more difficult to learn. Nine of the participants slept for 3 hours. The other six stayed awake, and all of them were scanned again using MEG and PSG.

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An hour later, each participant was asked to perform the finger-tapping task. The results of this experiment found that those who slept performed the task faster and more accurately, compared with those who stayed awake.

Next, the participants were scanned using magnetic resonance imaging (MRI) to see where the rhythmic neural activity (brainwave oscillations) observed earlier was located in each participant’s brain.

What the researchers discovered was five different oscillations over eight different brain regions (four on each side of the brain).

The researchers had expected that the most significant activity would be in the region of the brain responsible for motor control, but what they found instead was such activity occurred in a region in the top-middle of the brain called the supplementary motor area, or SMA.

Accordingly, the researchers then used caps of EEG sensors to further measure brainwave changes in each participant. As a result, they discovered that the brainwave changes occurred during a specific phase of sleep called "slow-wave" sleep.

The study found that two specific brainwave oscillations were identified in a region in the top-middle of the brain (SMA), which plays a role in the "reorganization" function that the brain carries out during sleep to aid motor learning.

These findings fulfilled two criteria established by the researchers at the start of the study: 1) the rhythmic neural activity, or oscillations, changed substantially after the subjects were trained in the finger-tapping tasks; and 2) the strength of that change was tied to how much the participant's performance improved on each task.

The study authors report that they have already started another study in an effort to learn more about how the brain consolidates the learning of visual tasks – and they would like to see if similar frequency bands can be found within a similar organization of brain areas.

SOURCE: Enhanced spontaneous oscillations in the supplementary motor area are associated with sleep-dependent offline learning of finger-tapping motor-sequence task, The Journal of Neuroscience, 21 August 2013, 33 (34): 13894-13902 (doi:10.1523/JNEUROSCI.1198-13.2013).

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