Mental representations, liberated from sensory experience and motor actions, are the foundation of abstract thought. The ability to use mental representations to guide behavior is probed in working memory tasks, in which information must be remembered for several seconds to guide a subsequent behavioral response. How did these representations arise during evolution of the brain? This is a question of paramount importance to our understanding of the brain and cognition. Our international team of researchers in the United States, Canada, and Germany is working to understand this question from the genetic code for single ion channels to the networks of millions of neurons that underlie working memory in the brain.

Mental representations that are independent of sensory input and the execution of motor output are a step up in brain evolution: they exist in a “virtual space”, so that the brain can use information acquired in the past to solve complex problems, “simulate” situations, and “predict” future outcomes without the need to invest energy in motor actions. Current evidence indicates that representations of this kind arose relatively late in evolution, with the development and expansion of the prefrontal cortex (PFC). Working memory representations may hold the key to human intelligence and evolutionary success, as well as to understanding complex disorders of the mind such as schizophrenia.