The human brain is activated even before a stimulus occurs if a person knows the stimulus will happen within a few seconds. The neural basis for this cognitive function, termed anticipation, is the subject of this review. One method for investigating the brain mechanism of anticipation employs stimulus-preceding negativity (SPN), which is a type of event-related potential (ERP). A critical feature of SPN is that SPN amplitude is greater at the right than at the left hemisphere. This feature suggests that the right hemisphere plays a significant role in the anticipation process. Some neuroimaging studies identified the anterior insula as a physiological source of SPN. The anterior insula is a part of the salience network that detects stimulus salience. Furthermore, recent neuroimaging studies reveal that the right anterior insula is involved in processing the salience outcome, whereas the left anterior insula is related to behavioral adaptation. The SPN study combining functional magnetic resonance imaging (fMRI) and ERP revealed that the right anterior insula showed increased activity preceding a stimulus, while the left anterior insula was not activated. Such studies lead to the hypothesis that saliency of an anticipated stimulus evokes the salience network in advance of a stimulus, and that this network then pre-activates other brain regions in perception of an anticipated stimulus. These processes can be shown as SPN variations in amplitude and cortical distribution. In general, SPN studies suggest that the saliency of an anticipated stimulus is a key factor in evoking anticipatory brain activity. Keywords : stimulus-preceding negativity, insular cortex, salience network
Anticipation and event-related potentials (ERP)Anticipation is a cognitive phenomenon characterized by an individual's preparatory state of mind with respect to a forthcoming event or stimulus. Anticipation facilitates overt behavioral responses that render it possible for the individual to react faster to such events than without anticipation. On the other hand, anticipating an unwanted stressful event in the near future, for example, a student concerned about an upcoming examination, may sometimes also trigger strong anxiety. Investigating the neural mechanism of anticipation is also crucial for understanding how athletes exhibit fast and accurate movements in games, and why, on the other hand, some patients suffer from anticipatory anxiety in hospitals. In this review, we introduce studies concerned with stimulus-preceding negativity (SPN) that reflect anticipation. This entails a discussion of the neural mechanisms that underlie SPN and it leads to the revelation of a key factor in the evocation of brain activity related to anticipation.Studies on human brain activity related to anticipation date from the 1960's when the use of event-related potential (ERP) became popular 1) . The ERP is calculated from the electroencephalogram (EEG). To calculate ERP, an EEG is first determined by a duration with times fixed before and after reco...