The Taylor Manifest Anxiety Scale was used to rank 24 healthy student volunteers according to trait anxiety level. A bipolar occipital scalp electrode was used to record the resting eyes-closed EEG responses to 15 ‘neutral’ tone stimuli and response to stress inducing questions.
Eighteen subjects responded to the experimental paradigm by showing phasic changes in alpha-type synchronization. In response to 15 neutral tone stimuli, 13 (73%) subjects yielded mean alpha blocking scores, while 5 subjects (28%) had mean augmentation scores. Across all 18 subjects, trait anxiety was found to be significantly correlated with alpha response tendency to tone. The high trait anxiety group, when compared to low anxiety group, showed a significantly greater tendency toward alpha augmentation both in response to sound stimuli and stress questions. No significant correlation was found between trait anxiety and the resting alpha index. Alpha response tendency to tone stimuli was significantly correlated with the resting alpha index over the entire population of 24 subjects, and for 12 subjects of the high anxiety group alone.
When alpha responses were measured regardless of direction (alpha blocking or augmenting), the high anxiety group, compared to the low anxiety group, was much more homogeneous in the magnitude of responses, as shown by smaller group mean values during various phases of acute stress and significantly smaller variance of the means. When the individual mean responses during various phases of stress were measured, taking into account the direction and magnitude of responses and particularly their variance, subjects in the high anxiety group were significantly more consistent and predictable than subjects in the low anxiety group.
The possible relationship between alpha enhancement, internal inhibitory processes, and behavioral rigidity was discussed.
Six subjects responded to the experimental paradigm with predominance of 5–6/sec theta activity which was felt to be a genuine neocortical pattern associated with internal inhibitory processes. The results were analyzed by excluding and including the ‘theta subjects’.