Figure 3.

Biorhythms from different nervous systems and motor/behavioral results from cognitive load. (A) Biorhythm of motor signals, from hand pointing movements, in the form of temporal speed profiles across 60 trials, exhibit moment by moment variations with different levels of cognitive load. Motions are aligned to the touch of the screen and heat maps are used to show the speed peaks (cm/s) for the forward and backwards motions. Peaks of the electro-cardiogram signals (ECG) are aligned (4 s) and represented in (B) as spikes. Later in the analyses, these peaks become standardized as unit-less micro-movements ranging on the real-valued scale from 0 to 1 for further stochastic analyses (see “Materials and Methods” section). (C,D) To validate the effect of cognitive load, movement time (i.e., time was registered from the time when the participant was prompted to reach the target, to time of completion of the reach by touching the screen), error in time estimation, and average number of angular acceleration peaks per trial were compared between the high and low cognitive load conditions, and between pointing and time estimation tasks. Movement time showed significant difference between control and high cognitive load condition (t₍₈₎ = 3.53, p < 0.01) and between low and high cognitive load condition (t₍₈₎ = 0.15, p < 0.01). Error in time estimation also showed significant difference between control and high cognitive load condition (t₍₈₎ = 2.89, p = 0.04) and low and high cognitive load condition (t₍₈₎ = 4.21, p < 0.01). Number of angular acceleration peaks were significantly different between low and high cognitive load conditions for forward motions (t₍₈₎ = 5.4, p < 0.01) and backward motions (t₍₈₎ = 7.6, p < 0.01); and between pointing and time estimation tasks for forward motions (t₍₈₎ = 2.2, p = 0.05) and borderline significant for backward motions (t₍₈₎ = 2.1, p = 0.07). **p < 0.01; *p < 0.05. The experimental paradigm described in Figure 2 proved efficient to probe cognitive demands and characterize cognitive loads by time series of peaks in trajectories described by the hand’s angular acceleration. See Supplementary Tables S2–S4 for all pairwise comparisons of these metrics.