HOW DO WE PREDICT THE CONSEQUENCES OF OUR ACTIONS - A FUNCTIONAL IMAGING STUDY

Humans are readily able to distinguish expected and unexpected sensory events. Whether a single mechanism underlies this ability is unknown. The most common type of expected sensory events are those generated a s a consequence of self-generated actions. Using H-2 O-15 PET, We Stud ied brain responses to such predictable sensory events (tones) and to similar unpredictable events and especially how the processing of pred ictable sensory events is modified by the context of a causative self- generated action. Increases in activity when the tones were unpredicta ble were seen in the inferior and superior temporal lobe bilaterally, the right parahippocampal gyrus and right parietal cortex. Self-genera ted actions produced activity in a number of motor and premotor areas, including dorsolateral prefrontal cortex. We observed an interaction between the predictability of stimuli and self-generated actions in se veral areas, including the medial posterior cingulate cortex, left ins ula, dorsomedial thalamus, superior colliculus and right inferior temp oral cortex. This modulation of activity associated with stimulus pred ictability in the context of self-generated actions implies that these areas may be involved in self-monitoring processes. Detection of expe cted stimuli and the detection of the sensory consequences of self-gen erated actions appear to be functionally distinct processes, and are c arried out in different cortical areas. These observations support the oretical approaches to cognition that postulate the existence of a sel f-monitoring system. (C) 1998 Elsevier Science Ltd. All rights reserve d.