Fig. 1.

Illustration of the sampled brain regions and the percentages of intracranial sigma band activity at time of scalp spindles. The circles correspond to the investigated brain regions. The area of the circles is proportional to the number of investigated channels in each brain structure, and the color indicates the percentage of channels in which a statistically significant increase in sigma band energy (10–16 Hz) was observed during the scalp spindle intervals compared to the control intervals (with Holm–Bonferroni correction for multiple comparisons).