A qualitative and quantitative analysis of rhythmic activities during a mental task and sleep spindles

The frequency, configuration, and distribution of sleep spindles are similar to some of the rhythmic activities seen during task performance. In the present study, the relationship between rhythmic activities during sleep and arithmetic addition was investigated in male university students with (n = 10) and without (n = 10) frontal midline theta activity (Fmtheta). Electroencephalograms (EEGs) during addition in both groups were compared at frontal and central areas on three consecutive days. Polysomnograms were recorded at the same regions on four consecutive nights for each group. The amount of theta rhythm during a mental task (Fmtheta) and in nocturnal sleep at Fz and Cz electrodes was greater for the Fmtheta group than for the non-Fmtheta group, while the amount of beta rhythm at both sites was smaller in the Fmtheta group than in the non-Fmtheta group. There were no differences between the groups in the amount of alpha rhythm at either site. The frequency of alpha rhythm at Fz and Cz in both situations was slower for the Fmtheta group than for the non-Fmtheta group, but there were no differences in the frequency of theta and beta rhythms between the groups at either site. These results suggest that rhythmic activities during a mental task and in sleep may correlate with each other.