Coordination between the left and right limbs during cyclic movements, which can be characterized by the amplitude of each limb's oscillatory movement and relative phase, is impaired in patients with Parkinson's disease (PD). A pedaling exercise on an ergometer in a recent clinical study revealed several types of coordination disorder in PD patients. These include an irregular and burst-like amplitude modulation with intermittent changes in its relative phase, a typical sign of chaotic behavior in nonlinear dynamical systems. This clinical observation leads us to hypothesize that emergence of the rhythmic motor behaviors might be concerned with nonlinearity of an underlying dynamical system. In order to gain insight into this hypothesis, we consider a simple hard-wired central pattern generator model consisting of two identical oscillators connected by reciprocal inhibition. In the model, each oscillator acts as a neural half-center controlling movement of a single limb, either left or right, and receives a control input modeling a flow of descending signals from higher motor centers. When these two control inputs are tonic-constant and identical, the model has left-right symmetry and basically exhibits ordered coordination with an alternating periodic oscillation. We show that, depending on the intensities of these two control inputs and on the difference between them that introduces asymmetry into the model, the model can reproduce several behaviors observed in the clinical study. Bifurcation analysis of the model clarifies two possible mechanisms for the generation of disordered coordination in the model: one is the spontaneous symmetry-breaking bifurcation in the model with the left-right symmetry. The other is related to the degree of asymmetry reflecting the difference between the two control inputs. Finally, clinical implications by the model's dynamics are briefly discussed.
We investigated changes in blood pressure with exercise, including walking and ergometer training, sleep, and body weight. Blood pressure was monitored over a period of about 1 year in 61 subjects in Osaka, Japan. The morning systolic blood pressures were analyzed using multivariate regression analysis, and the correlations between systolic blood pressure and the above parameters were determined. The systolic blood pressure distribution was classified into improved, stable, and ingravescence groups. In the improved group, exercise intensity and total calories were important factors controlling the systolic blood pressure. More than 300 kcal per day was needed to improve the systolic blood pressure. In the stable and ingravescence groups, body weight control was also an important factor in maintaining blood pressure. An increase of 1 kg in body weight was associated with systolic blood pressure increases of 3 and 6 mm Hg in the stable and ingravescence groups, respectively. The long-term repeated use of home blood pressure testing may be a good self-care strategy for monitoring daily health.
Intralimb incoordination needs to be distinguished from interlimb incoordination, which is observed in Parkinson's disease (PD). With this aim, intra and inter-limb coordination impairment in the lower limbs were measured in 13 patients with cerebellar ataxia during pedaling of an ergometer with left and right pedals that can be rotated independently. Intralimb incoordination in patients with cerebellar ataxia was compared with interlimb incoordiation in patients with PD. We concluded that impairment of intralimb coordination in ataxia patients leads to inability to maintain pedaling amplitude and speed, but unlike in PD, right and left coordination was roughly preserved. Our method may be useful for assessing the severity of ataxia and detecting hidden parkinsonism in ataxic patients.
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