Ten human subjects were comparing durations of pairs of visual stimuli in a two-way forced-choice task. Mean durations of presented time intervals were ~3 s ('short') or ~6 s ('long'); the duration ratio was varied at nine levels. The Weber fractions for the short and long durations were approximately equal, ~0.22. The ratio of subjective equality was almost exactly unity for the short durations, but it was significantly reduced (~0.76) for the long durations. This asymmetry of the discrimination function indicates time-dependent change of internal representations of past durations, and is well compatible with the 'dual klepsydra model'. Model-based estimates of the internal time representation loss rate, derived from the present data, are in a good agreement with values obtained from earlier studies on duration reproduction.
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Complexity of EEG (W), a global measure reflecting degree of spatial synchronization, was computed for whole night recordings of sleep EEG of 10 healthy volunteers, 9 males and 1 female (age 21-53) and 6 depressive patients, 5 males and 1 female (age 23-64). Sleep was scored visually in 20's epochs, W was calculated in 2.5 s segments and the median from 8 segments (20 s) was calculated. W was calculated for the whole field of 21 electrodes and for the left and right hemisphere separately (2 x 8 electrodes). Measure of global power (S) and generalized frequency (f) were also computed for the same data. In healthy subjects the complexity was higher over the right hemisphere during waking, and the difference shifted to higher complexity over the left hemisphere in slow wave sleep (F=5.15, df1=4, df2=6856, P<0.0005). The opposite trend was found in depressives (F=10.51, dfl=4, df2=3960, P<0.0001).
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