Alpha Enhancement: Effectiveness of Two Feedback Contingencies Relative to a Resting Baseline.

To investigate the effectiveness of informational feedback in the enhancement of the occipital alpha rhythm, 29 subjects were given one session of feedback in which either the presence of a tone signalled alpha (Loop 1) or the absence of tone signalled alpha (Loop 2), while 11 controls received no feedback. Alpha obtained during these conditions was compared to baselines established from maximum eyes closed rating alpha densities obtained in an earlier session. The Loop 1 group increased alpha across feedback trials but did not exceed baseline, while Loop 2 subjects exceeded baseline but showed little increase across feedback trials. Controls showed no significant change in alpha. Enhancement across trials was associated with individual differences in baseline alpha, with only those subjects in the mid-range of the distribution showing increases. These result do not verify claims large magnitude changes in alpha density with feedback training, but do suggest that methods of feedback presentation other than the customary Loop 1 contingency may be more effective in facilitating short term increases in alpha above resting baseline. [ABSTRACT FROM AUTHOR]