Neuroscientists have long pondered what makes us act on some thoughts and not others and a new discovery could be the key to treating some mental disorders.
Past research has suggested that particular clusters of neurons represent each of the millions of thoughts that we generate, but no one has been able to work out exactly how they function.
Now, researchers from Boston University and Massachusetts Institute of Technology (MIT) believe that conscious thought might be rhythmic.
The US neuroscientists think our brains form thoughts and decisions when particular groups of neurons move in particular ways to respond to certain cues or rules.
"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," Earl Miller, an MIT Professor of Neuroscience, said in a media release.
"That’s the fundamental problem that we’re talking about — the very nature of thought itself."
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The researchers made their discovery by studying a group of monkeys who had been trained to respond to objects based on colour or their orientation (positioning).
As the animals switched between tasks, the researchers were able to identify two neural groups by measuring brain waves.
When the animals were using positioning to respond to objects, a particular group of neurons oscillated at high frequencies. But when the animals were responding to objects based on colour, a different group of neurons began moving rapidly.
When the colour rule was being applied, the researchers noticed that the orientation-related neurons still oscillated, but in low frequencies, which the researchers believe help to dim the neurons that trigger the orientation thoughts.
“What this suggests is that orientation was dominant, and colour was weaker," Miller said.
"The brain was throwing this blast of [low frequency waves] at the orientation ensemble to shut it up, so the animal could use the weaker ensemble.”
Now the researchers believe interference with these oscillations could play a part in neurological disorders such as schizophrenia.
“It’s one of the biggest mysteries of cognition –– what controls your thoughts,” Miller said.
“The most fundamental characteristic of consciousness is its limited capacity. You only can hold a very few thoughts in mind simultaneously."
Professor Colin Masters, director of the Mental Health Research Institute at the University of Melbourne, told ninemsn the research fills a missing piece of the neuroscience puzzle.
"There's different rhythms in the brain and nobody has really understood their complexity. What this shows is that it is possible to relate some of these rhythms and oscillations in the brain with behavioural tasks," said Professor Masters, who also works with the Florey Institute of Neuroscience and Mental Health.
"It begins to explain some of the limitations of what our brains are capable of doing. The researchers talk about how we are really only able to manage a few thoughts at a time and it may show why the brain has a certain relative capacity in some areas."
The next step is do research on human brains.
"Now we want to translate that into human studies," Professor Masters said.
"You can put electrodes into the brains of monkeys but you can't do that so easily in humans."
The study was published in the journal Neuron.