Why do we need to sleep? Well, for one thing, that's when our brains sort and process what we've learned during the day, storing it away as memories. When people suffer from conditions such as Alzheimer's, autism or schizophrenia, however, that function can be compromised. Now, scientists at the University of North Carolina have discovered that help for such individuals may lie in the form of zapping their brains while they sleep.

The electrical activity of our brains oscillates or alternates as we sleep, in waves of activity known as sleep spindles. While it had already been suspected that these spindles were involved in memory formation, it wasn't known if they actually caused memories to form, or were simply a by-product of the process.

Led by Dr. Flavio Frohlich, the UNC researchers decided to find out. They did so via a study involving 16 mentally-healthy male participants, whose sleep was monitored for two consecutive nights. Each night before going to bed, they performed two types of memory exercises. One was an associative word-pairing test, and the other called upon them to repeatedly finger-tap a specific sequence. The following morning, they had to repeat those same exercises, drawing on what they remembered from doing them the previous evening.

On one night, using electrodes placed on their scalps, their sleep spindles were monitored and then boosted via a process known as transcranial alternating current stimulation, or tACS. The other night, they received a placebo random stimulation, that wasn't synchronized to their spindles.

When they were tested on the exercises the next morning, they did better on the finger-tapping test after having received the tACS that synced up with their sleep spindles. According to Frohlich, this proves that the spindles are a crucial component of motor memory formation, and that manipulating them can enhance memory.

"We're excited about this because we know sleep spindles, along with memory formation, are impaired in a number of disorders, such as schizophrenia and Alzheimer's," says Dr. Caroline Lustenberger, a postdoctoral fellow in the Frohlich lab. "We hope that targeting these sleep spindles could be a new type of treatment for memory impairment and cognitive deficits."

Plans now call for the tests to be performed on people with known sleep spindle deficits.