When we get the new idea, we call it a brainwave. New research suggests that it may not be such a misnomer after all!. The research team, led by Earl Miller, the Picower Professor of Neuroscience at MIT, identified groups of neurons that emit certain brain waves when a particular thought was being processed. The study from researchers at MIT and Boston University sheds light on how neural ensembles form thoughts and support the flexibility to change one's mind.
The team, that published their findings in the Nov. 21 issue of Neuron, suggests our conscious thought may be rhythmic in nature. "As we talk, thoughts float in and out of our heads. Those are all ensembles forming and then reconfiguring to something else. It's been a mystery how the brain does this," says Miller, who is also a member of MIT's Picower Institute for Learning and Memory. "That's the fundamental problem that we're talking about — the very nature of thought itself."
As part of the study, the researchers trained a group of monkeys to do two different tasks - one based on the orientation involved and the other based on the colour involved. As the animals switched between tasks, the researchers measured the brain waves produced in different locations throughout the pre-frontal cortex, where most planning and thought takes place. Those waves are generated by rhythmic fluctuations of neurons' electrical activity.
When the animals responded to objects based on orientation, certain neurons oscillated at high frequencies called beta waves. When color was the required rule, a different ensemble of neurons oscillated in the beta frequency. Some neurons overlapped, belonging to more than one group, but each ensemble had its own distinctive pattern.
This work could also help in unravelling the neural basis of consciousness.
"The most fundamental characteristic of consciousness is its limited capacity. You only can hold a very few thoughts in mind simultaneously," Miller says. These oscillations may explain the reason. Previous studies have shown that when an animal is holding two thoughts in mind, two different ensembles oscillate in beta frequencies, out of phase with one another.
"That immediately suggests why there's a limited capacity to consciousness— Only so many balls can be kept in the air at the same time, only a limited amount of information can fit into one oscillatory cycle," Miller says. Problems in these oscillations may lead to neurological disorders such as schizophrenia.
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