Deep sleep may reinforce new motor skills

Deep sleep can help the brain reinforce newly learnt motor skills that involve handling objects, Indian-origin scientists have found.

Researchers at University of California San Francisco in the US found that during non-rapid eye movement (REM) sleep, slow brain waves bolster neural touch points that are directly related to a task that was newly learned while awake, while weakening neural links that are not.

"This phenomenon may be related to the notion of 'extracting the gist' of how to perform a novel task. Sleep appears to reduce neural activity that is not related to a task we are in the process of learning," said Karunesh Ganguly, associate professor at UC San Francisco.

Researchers used a system known as a brain-machine interface (BMI) to better understand how the brain picks up new skills during sleep.

They implanted electrodes in the motor region of rats' brains to send electrical signals to a computer, which then drove movement of a detached mechanical device.

Since neural circuits are dynamic, the rats' brains rewired themselves to control this device just as swiftly as they would have if the rats were practising new ways to control their own limbs.

"A particular neuron may normally be devoted to controlling a limb, but we can create a new relationship of that neuron with an external disembodied device," said Tanuj Gulati, a postdoctoral scholar at UC San Francisco.

"A particular neuron may normally be devoted to controlling a limb, but we can create a new relationship of that neuron with an external disembodied device," said Gulati, lead author of the study published in the journal Nature Neuroscience.

Researchers connected neurons in rat brains to implanted electrodes, which controlled a mechanical waterspout. The source of water was behind a tiny door facing away from the mice.

Since the spout faced away, the rats had to learn to use a computer-driven mechanism to move it toward them. As the rats explored several strategies to control the spout, some of which included overt movements, they sometimes activated neurons adjacent to the electrodes.

When the proper neurons were activated, the computer moved the waterspout, researchers said.

"Eventually the rats learn to delink actual movements from the spout they know they don't really need to flinch their arm or do anything to make it move," Gulati said.

"All they have to do is volitionally control the pipe and it will come to them," he added.

Researchers noted that once rats got the hang of the task while awake, certain neural patterns kept 'replaying' during sleep.

"This shows that you can not ignore sleep. Whether you are trying to do it in patients trying to regain movement control after a neural injury, or healthy individuals trying to learn a new skill," Gulati said.