Effect of mind on brain activity: Evidence from neuroimaging studies of psychotherapy and placebo effect

Mentalistic variables must be considered to reach a correct understanding of the neurophysiological basis of behavior in humans. Confusion regarding the relative importance of neurophysiological and mentalistic variables can lead to important misconceptions about causes and effects in the study of human behavior. In this article, we review neuroimaging studies of the effect of psychotherapy in patients suffering from diverse forms of psychopathology (obsessive-compulsive disorder, panic disorder, unipolar major depressive disorder, spider phobia). We also review neuroimaging studies of the placebo effect in healthy individuals (placebo analgesia, psychostimulant expectation) and patients with Parkinson's disease or unipolar major depressive disorder. Mental functions and processes involved in diverse forms of psychotherapy exert a significant influence on brain activity. With regard to the placebo effect, beliefs and expectations can markedly modulate neurophysiological and neurochemical activity in brain regions involved in perception, movement, pain and various aspects of emotion processing. The findings of the neuroimaging studies reviewed here strongly support the view that the subjective nature and the intentional content of mental processes significantly influence the various levels of brain functioning (e.g. molecular, cellular, neural circuit) and brain plasticity.