This is brought out by the differential effects of low-frequency stimulation on the variation in tapping intervals, evident in differences in the coefficient of variation and hence independent of any differences in tapping rate.
For the equalizer of the present study, the tap interval is the reciprocal of the symbol rate, i.e., the symbol interval; if the equalizer before the matched filter transmits pulse after a channel distortion, then this tap interval is optimal.
This simple model supports a set of easily testable hypotheses: (1) the timekeeper variance should present a Weberian increase with target interval length, (2) motor variance should be independent on target interval length, and (3) inter-tap interval series should present a negative lag-one autocorrelation, bounded to −0.5.
For the calculated inter-tap interval there was the same effect than for absolute frequencies (F 2,31) = 19.45; p<.001) with the pHDs and controls not differing from each other (controls: 352.46±15.11; pHD: 363.39±15.13) (p>.9) and performing better than the HD-group (480.43±16.55) (p<.001).
In case of a stable vigilance state within these three seconds, i.e. three equal VIGALL-vigilance classifications within the three-second-sequence, trials were included for calculating the average vigilance-specific re-tapping interval length per subject.
In the cross-sectional study, not only were the number of taps determined, but also the variability in the time between successive taps (the inter-tap interval).
No significant (P < 0.05) correlations were seen with any other regional graph metric and Stroop word reading, symbol digit modalities or Speeded Tapping mean inter-tap interval.
If this data was also collected for the longitudinal study, then both the number of taps and the variability of the inter-tap interval could have been plotted over time.
The lack of correlation of Stroop word reading, symbol digit modalities or Speeded Tapping mean inter-tap interval with rich club graph theory measures suggest that these tasks may be less dependent on optimal communication between diverse brain regions.
Participants were assessed using symbol digit modalities (Smith, 1968), Stroop word reading (Stroop, 1935), Indirect Circle Tracing (log of the indirect circle annulus) (Say et al., 2011; Tabrizi et al., 2011), Negative Emotion Recognition (Ekman and Friesen, 1976), Speeded Tapping (mean inter-tap interval non-dominant hand) (Reilmann, 2005) and total motor score (Huntington Study Group, 1996).
