Table 1.
Demographics of the participants.
Fig 1.
Temporal order judgment in the arms-uncrossed condition.
(A-C) The order-judgment probability (ordinate) that the right hand was stimulated earlier than the left is plotted against the stimulation onset asynchrony (SOA, abscissa) for the young (A, circles), non-PD elderly (B, squares), and PD elderly participants (C, triangles). A positive SOA indicates that the right hand was stimulated first. The sigmoid curves indicate the results of the model fitting (Equation 1). A broken curve in (B) shows the result for the non-PD elderly participants and the same broken curve is superimposed in (A) and (C) for the sake of comparison with the young (A) and elderly-PD participants (C). Each symbol represents 160 (A, 8 trials×20 participants), 184 (B, 8×23), and 192 trials (C, 8×24) trials. (D) Group comparisons of temporal resolution. Each box in the box-plots show the 25, 50 (median), and 75 percentiles. The whiskers extend to the most extreme data points not considered as outliers that falls outside the range of 1.5 times of the interquartile range from either end of each box. The brackets with asterisks indicate that the median was significantly different (p < 0.05/3, Wilcoxon rank sum test after Bonferroni corrections for multiple comparisons).
Table 2.
Comparison of the mean model parameters.
Fig 2.
Temporal order judgment in the arms-crossed condition.
(A-C) The red symbols indicate the probability of a right-hand first judgment in the arms-crossed condition plotted against the SOA for the young (A), non-PD elderly (B), and PD elderly participants (C). The black and red curves indicate the results of the model fitting in the uncrossed (Equation 1) and crossed (Equation 2–4) conditions. Each symbol represents 144 (A, 8×18), 184 (B, 8×23) and 128 (C, 8×16) trials. The other conventions are as in Fig. 1A. (D-F) The difference between the order-judgment probability in the crossed and uncrossed condition (ordinate) are plotted against the stimulation onset asynchrony (SOA, abscissa). The difference shown in (D), (E), and (F) was calculated using data from the young (A), non-PD elderly (B), and PD elderly participants, respectively. The upward and downward Gaussian curves (blue) correspond to the flip functions, fl and fr, of the judgment probabilities as defined in Equations (3) and (4). The net peak flip amplitudes (Ãl and Ãr in Equations (5) and (6)) and the probability of generic error (c in Equations (3) and (4)) are indicated in (F). (G-L) Group comparisons: the net left-to-right flip probabilities (Ãl) (G), those of the reverse (Ãr) (H), the constant error rate (c) (I), the time window of the flip (σf) (J), and error response rates in the catch (K) and the single stimulus trials (L). The box-plot conventions are as Figs. 1D-F. The brackets with asterisks show that the median was significantly different (p < 0.01, Wilcoxon rank sum test after the Bonferroni correction for multiple comparisons). (M) The time window of the flip (σf, ordinate) plotted against the constant error rate (c, abscissa). Data from the young (circles), non-PD elderly (squares), and PD elderly participants (triangles) are shown with different symbols. Note a significant correlation between the two parameters (Spearman’s ρ = 0.36, p = 0.0055).
Fig 3.
The mean reaction time (ordinate) is plotted against the SOA (abscissa) for the young (A), non-PD (B), and PD participants (C). The colors differentiate between the arms-crossed (red) and -uncrossed (black) conditions.