Professor of Biology, Boston University 

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"The neuroscience of imagination and evolution of language"

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Your brain is a bizarre device, set in place through the natural selection of your ancestors and your own experience. One thing that clearly separates your brain from the brain of any other non-human animal is the propensity of your brain for imagination and creativity. In this discussion, we will dive into the neuroscience of imagination: What makes your brain unique? What were the selectional forces that shaped the brains of our ancestors? Did Neanderthals communicate? What enabled humans to become the dominant species on the planet? These questions cannot be addressed without a clear understanding of the neurological difference between voluntary and involuntary imagination. A vivid and bizarre dream conjures up a myriad of novel mental images. The same exact images can be created volitionally when awake. The neurological mechanisms of these two processes are different. Voluntary combination of mental objects is mediated by the lateral prefrontal cortex (LPFC) and patients with damage to the LPFC often lose this ability. Conversely, the combination of mental objects into novel images during dreaming does not depend on the LPFC: LPFC is inactive during sleep and patients whose LPFC is damaged do not notice a change in their dreams. Paradoxically, few scientists are aware of the difference between mechanisms of imagery during dreaming and waking. Furthermore, neither colloquial English nor scientific jargon have an established way to report on the origin of a conjured up mental image: the term “imagination” is regularly used to describe any experience generated internally whether voluntarily (in waking) or involuntarily (in dreaming). Failing to distinguish between voluntary and involuntary imagination leads to confusion in developmental psychology, neurolinguistics, and paleoanthropology. A comprehensive understanding of the distinction between voluntary and involuntary imagination will contribute to a clearer understanding of the uniqueness of human language, enable a more productive discussion of the evolutionary origin of human language, and help develop better therapy for children with language delay.