Oct. 11 (UPI) -- When neurons fire in the brain, they release a unique electrical signal that reverberates at distinctive frequencies. New research suggests different types of learning correspond with different brainwave frequencies.
The revelation -- detailed in a new paper published this week in the journal Neuron -- could help doctors diagnose and treat learning disabilities and cognitive diseases.
Since the 1950s, neuroscientists have understood that there are two kinds of learning and memory -- explicit and implicit.
According to Earl K. Miller, a professor of neuroscience at MIT, explicit learning is the type that a person is cognizant of and can describe. Examples of explicit learning would be memorizing a poem or studying for a geography test.
"Implicit learning is the opposite. You might call it motor skill learning or muscle memory, the kind of learning that you don't have conscious access to, like learning to ride a bike or to juggle," Miller told MIT News. "By doing it you get better and better at it, but you can't really articulate what you're learning."
Often, complex tasks, such as learning to play a song on the piano, require both kinds of learning.
When Miller and his colleagues studied animal learning, they found different tasks required one type of learning or the other, and each type corresponded to different signals.
When required to compare and match two things, animals used explicit learning, recalling both correct and incorrect answers to improve their performance. But when trained to move their eyes in one direction or the other in response to a visual stimuli, the animals' only improved their correct responses, suggesting the use of implicit learning.
During explicit learning, researchers found alpha2-beta brain waves corresponded with correct responses while delta-theta wakes increased only after an incorrect response. Alpha2-beta frequencies also spiked when animals first learned a task. As animals repeated the task, alpha2-beta waves tapered off.
Researchers surmised that the initial spike in alpha2-beta brain waves represents the formation of a cognitive model needed to learn and absorb the task.
"And then after the animal learns the task, the alpha-beta rhythms then drop off, because the model is already built," Miller said.
During implicit learning, correct answers corresponded with spikes in delta-theta waves. These waves also tapered off as the motor skill became engrained.
The realization that different types of learning work in unique ways could help scientists and educators improve the kinds of help offered to people as they learn new tasks -- whether they have a learning disability or not.
Another recent study found a region of the brain -- called the brain's dendrites -- are excited by unique brainwaves called spindles during sleep. Spindles trigger dendrites to help incorporate new memories and information into the neural infrastructure. Scientists hypothesized that the frequency of spindles could be mimicked to trigger dendrite activity in patients with memory loss.
Similarly, Miller and his colleagues at MIT believe their work could lead to new treatments for Alzheimer's.
"In Alzheimer's, a kind of explicit fact learning disappears with dementia, and there can be a reversion to a different kind of implicit learning," said Roman F. Loonis, a graduate student in the Miller Lab. "Because the one learning system is down, you have to rely on another one."