Cumulative benefits of frontal transcranial direct current stimulation on visuospatial working memory training and skill learning in rats

Transcranial direct current stimulation (tDCS) of the prefrontal cortex, which non-invasively alters cortical activity, has been established to affect executive functions in humans. We hypothesized that changes in excitability by tDCS, found to improve cognitive functions dependent on moderate prefrontal cortex activity, would operate similarly in animals as in humans. To verify this we performed experiments using a rat behavioral model of visuospatial working memory and skill learning paired with tDCS of the frontal cortex. The effect of anodal/cathodal tDCS was examined in three sessions using the allothetic place avoidance alternation task (APAAT) and later re-examined without stimulation. Stimulation had no measurable short term effect on on-going place avoidance learning. However, in the follow-up session on day 21 the rats previously treated with cathodal tDCS showed significantly more efficient place avoidance and skill retention in comparison to the controls. This demonstrates a long-term benefit of diminished excitability by frontal tDCS when paired with training on working memory and skill learning in a novel task. The presented behavioral model provides a tool to evaluate the underlying mechanisms of how tDCS modulates neural network function to support successful behavior. (C) 2011 Elsevier Inc. All rights reserved.