Effect of precision aiming on respiration and the postural-respiratory synergy.

Precision manual tasks require a stable postural background which might be facilitated by respiratory modulations. We investigated the influence of performing a manual precision aiming task on respiratory rate and dynamics, and the coherence between respiration and center of pressure (COP) fluctuations (i.e., the postural-respiratory synergy). Participants aimed a pointer at targets of different sizes while seated or standing. Respiratory rate increased during the aiming period compared to a pre-task phase, but did not vary as a function of aiming difficulty. Recurrence quantification analysis revealed an increased incidence of slowly changing periods of chest movements during the most difficult aiming condition, which required the highest level of manual precision. Aiming, irrespective of difficulty, led to increases in the regularity of the respiratory pattern. Increases in respiratory rate during aiming were accompanied by an increased level of coherence for the seated but not the standing posture, suggesting that task demands affect the organization of coordination across the postural-respiratory synergy. Functional demands of the task likely shape the effectiveness of compensation for respiration during precision aiming.

Deterministic center of pressure patterns characterize postural instability in Parkinson's disease.

Static posturographic recordings were obtained from six Parkinson's patients and six age-matched, healthy control participants. The availability of vision and visuo-spatial cognitive load were manipulated. Postural sway patterns were analyzed using recurrence quantification analysis (RQA), which revealed differences in center of pressure (COP) dynamics between Parkinson's and control participants. AP COP trajectories for the Parkinson's group were not only significantly more variable than for the control group, but also exhibited distinct patterns of temporal dynamics. The visual manipulation did not differentially affect the two groups. No cognitive load effects were found. The results are generally consistent with the hypothesis that pathological physiological systems exhibit a tendency for less flexible, more deterministic dynamic patterns.