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Neurology

The waves of intelligence

The pace of the brain's function may indicate improved learning ability

After nearly five years of work, neuroscientist Lucas Santos believes that he has finally obtained the initial evidence that the brain’s electric activity allows one to estimate the ability to learn.

It was not easy. For three years, he had to go to the University of São Paulo (USP) at very unconventional hours. He would arrive in the morning and stay until 3:00 a.m., long after all the professors and students had left the Cidade Universitária campus to go home. Santos spent hours at the laboratory of Maria Teresa Silva, housed in USP’s Psychology Institute, training white mice – that like to sleep during the day and run around at night – to press a lever and receive droplets of sugar-sweetened water as a reward.

He submitted the mice to tests to see if they discovered when and how to press the lever to get the reward. Then he used an electroencephalograph to record the electric activity of the neurons of the hippocampus, a region of the brain that coordinates memory acquisition and the level of attention, both of which are essential for the learning process.

Santos found that the hippocampus cells of the rodents that were able to learn more or more easily triggered a higher number of electric communication signs with other parts of the brain every second than the cells of the rats that took longer to discover how to feed themselves during the experiments. On average, the hippocampus electric activity in the smarter animals was nearly 30% higher than that of the rodents that did more poorly in the tests.

Elaborate network
In the electroencephalograph, the electric signs of the hippocampus appear as theta waves. These were first identified in 1938 by German physiologists Richard Jung and Alois Kornmüller and are among the four known types of electric brain waves. In the case of the rats that performed better in the learning tests, the theta waves achieved an average frequency of 9 hertz, corresponding to nine discharges per second. In the case of the other animals, the average frequency came to roughly 7 hertz, or seven electric discharges per second, as described by Santos and his collaborators in an on-line article in the February issue of the journal Behavioral and Brain Research.

In Santos’ opinion, the accelerated functioning of the hippocampus might be a reflex of a more developed network of nerve cells. “The smarter animals probably have more elaborate circuits and a neurological base allowing for a higher attention level and facility to learn in these and other situations,” comments the Brazilian neuroscientist, who is currently working as a researcher at Brown University, in the United States.

Santos’ next steps will be to repeat the tests on bigger animals that are closer to human beings in evolutionary terms, such as cats, dogs and monkeys – and perhaps even develop experiments to test people. If new tests confirm these results, he will have proved a hypothesis launched nearly 50 yeas ago by professor César Timo-Iaria, one of the best known and respected Brazilian neuroscientists, who passed away in 2005 and with whom Santos worked from 1997 to 2004. “Professor César liked to use the world -intelligence- a controversial word, to describe acquired learning,” Santos recalls. “If he was right, then the theta waves might be a measure of the intelligence level.”

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