Fig. 4. Time-related changes of spatial EEG components (fig. 3) in the delta and alpha bands after treatment with 3.0 μg/kg clonidine. Given are mean principal component scores for 1-min intervals and their standard errors. The scores describe changes in the size of spectral power spatial patterns from baseline to postmedication periods. Clonidine exhibits topographically different effects, statistically significant (*) in the alpha and delta frequencies (table 2). For example, the spatial rotated component (rPC²) of alpha (black line), representing parietooccipital activity, was decreased after 3.0 μg/kg clonidine below baseline values during the whole observation period.