Variations in electroencephalographic alpha activity under conditions of differential lighting and auditory feedback

The electroencephalographic alpha activity of 13 college students was monitored under conditions of darkness or dim light for six sessions, and for a seventh under the opposite condition. Auditory feedback was given for the presence of alpha activity during a 5-min orientation period, and then during ten 2-min trial periods. The results indicated that: (1) alpha production in the presence of feedback did not exceed initial eyes-closed base line production; (2) introducing feedback immediately enhances alpha activity, rather than increasing production gradually; (3) under certain circumstances, dim light is sufficient to suppress alpha; and (4) after many sessions of alpha production in darkness, subjects maintain a given amount of alpha even when visual stimulation is present.