Neural efficiency in working memory tasks: The impact of task demand and training

Studies of human intelligence provide strong evidence for the neural efficiency hypothesis: More efficient brain functioning in more intelligent individuals, that is, less cortical activation in brighter individuals. The main goal of this study was to explore the relationship between intelligence and cortical activation in combination with a cognitive training. In 83 participants, cortical activation was assessed by means of event-related desynchronization (ERD) before and after working memory (WM) training. In a pre-test training post-test design, ERD during performance of trained as well as untrained transfer tasks was correlated with scores in a psychometric intelligence test (Raven’s Advanced Progressive Matrices test). We found a negative correlation between ERD and intelligence for moderately difficult tasks. A decrease in cortical investment from preto post-test was found for simple tasks but likewise for individuals with lower and higher intelligence. We could not find a stronger activation decrease from preto post-test for individuals with higher intelligence. These findings suggest partial confirmation of the neural efficiency hypothesis for moderately difficult tasks and they provide an indication that training can help in reducing cortical activation while solving simple tasks.