Non-invasive tDCS could increase performance of associative learning

Researchers at HRL Laboratories found that they could affect changes in functional connectivity between brain areas and thus increase learning speed.

The discovery comes after some controversy surrounding tDCS, with reports suggesting the use of the method shows no effect on neuron firing rates in cadaver heads – the original mechanism of interest. However, the new study conducted by HRL Laboratories confirms that behavioural changes speed up learning with tDCS and improve learning capability, regardless of neuron firing rates.    

The study, conducted in association with McGill University and Soterix Medical showed a 40% increase in learning speed when subjects were given 2 mA noninvasively to the prefrontal cortex without increased neuronal firing.

The behavioural task used in the study was associative learning, specifically a visual foraging task. The test subjects – macaques – had to learn arbitrary associations between visual stimulus and a location where they would then be rewarded.

Initial foraging took an average of 15 seconds and once the animal had learned the location of the reward, approximately 2 seconds. Subjects in the control condition took an average of 22 trials to learn and obtain the reward. Whereas with tDCS, subjects only required an average of 12 trials.

Speaking on the experiment, Dr. Praveen Pilly, HRL’s principle investigator, said:

“In this experiment we targeted the prefrontal cortex with individualized non-invasive stimulation montages. That is the region that controls many executive functions including decision-making, cognitive control, and contextual memory retrieval. It is connected to almost all the other cortical areas of the brain, and stimulating it has widespread effects. It is also the target of choice in most published behavioral enhancement studies and case studies with transcranial stimulation. We placed the tDCS electrodes on the scalp in both our control and stimulation conditions. The behavioral effect was revealed when they learned to find the reward faster.”

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