Uncertainty, anxiety, and brain oscillations.

Influence of anxious expectation on spectral power and delta-gamma coupling was studied in 39 subjects (27 females) aged 19-30 years who also filled out the State Trait Anxiety Inventory. The situation of uncertainty was associated with general increase in spectral power of all EEG bands, which was particularly pronounced in high-trait anxiety subjects. In low-trait anxiety subjects, association between delta and gamma power significantly increased when they had to expect bad news but did not change when they expected good news. In high-trait anxiety subjects, this association tended to increase in both cases. Higher baseline delta power predicted higher gamma power in the situation where a bad news was expected. These findings are discussed in terms of Gray and McNaughton's theory of anxiety and evolutionary interpretation linking delta oscillations with reward motivation. Increase of delta-gamma coupling in anxiogenic situation is interpreted to reflect higher cortical arousal, which appears in a frustrating situation in subjects with higher activity of "motivational" delta system.