Alpha blocking to the omission of a stimulus

Abstract

The study sought to demonstrate an increase in duration of alpha blocking to the omission of a scheduled stimulus and to examine the role of attentive state in producing the effect. Twenty male and 20 female subjects selected on the basis of consistent alpha rhythm were employed in a 2 by 2 by 2 design, the factors being presence or absence of the stimulus on the test trials, instructional set, and whether or not the subject was required to make a motor response to offset of the stimulus. EEG was recorded from the right and left hemispheres in response to a series of 5-sec pure tones of 100 dB presented at regular intervals of 20 sec. The stimulus was omitted on Trials 11, 22, and 33, and duration of alpha blocking was measured on the trials preceding and following the test trials and for an interval immediately prior to the test trials. Analysis indicated a significant increase in alpha blocking on the test trials for groups in which the stimulus was omitted, F(l,38) = 8.85, p