Brain functioning when the voices are silent: aberrant default-mode in auditory verbal hallucinations

Almost two decades of functional brain imaging has shown that auditory verbal hallucinations (AVH) in schizophrenia correspond with increased brain activity in a wide variety of different brain areas. However, these localized changes in brain activity are likely the end result of a more profound and fundamental aberration in brain dynamics that ultimately leads to the perception of hallucinated voices. AVH could arise from pathological brain states or modes that occur beyond moments of conscious AVH experiences. In other words, could AVH result from intrinsic brain activity at times when the voices are silent? Recent advances in functional brain imaging have shown that intrinsic brain states possess a rich and complex functional architecture that closely resembles brain dynamics observed during many different kinds of cognitive and sensorimotor tasks. Further, intrinsic brain states may prove to be of importance to goal-directed brain activity, and ultimately to our perception and performance, that is, of importance to our behavior. Pioneering studies provide the first indications that intrinsic brain states may play an important role in AVH and other psychotic symptoms in schizophrenia. This chapter describes the main fi ndings and advances in measuring intrinsic brain states in humans in vivo, and discusses how intrinsic brain states can contribute to our understanding of the setiology and experience of AVH in schizophrenia.