Periodic appearance of frontal midline theta activity during performance of a sensory-motor task.

The present experiment was designed to demonstrate the presence of a constant rhythm or periodicity in the appearance of Fm theta using the Mirror Drawing Test (MDT), a task with a changing degree of difficulty. Thirty male university students were recorded on the EEGs during performance of the MDT for 5 min. Fm theta appeared most frequently in the block requiring the longest time for passage, or the most difficult block. The present study further revealed that Fm theta tended to appear mainly from four points at about 40, 90, 190 and 270 sec after beginning the MDT. From these results, the appearance of Fm theta was shown to be more distinctly related to the concentration of attention. In the process of concentration and attention distraction, the presence of a rhythm with a periodicity of approximately 45 sec was suggested.