Effects of anodal stimulation and motor practice on limb-kinetic apraxia in Parkinson's disease.

Limb-kinetic apraxia, the loss of the ability to make precise, independent but coordinated finger and hand movements affects quality of life in patients with Parkinson's disease. We aimed to examine the effects of anodal transcranial direct current stimulation of the left posterior parietal cortex and upper extremity motor practice on limb-kinetic apraxia in Parkinson's disease. This study was conducted in a randomized, double-blind, sham-controlled fashion. Patients confirmed to have Parkinson's disease were recruited. Twenty-eight participants completed the study and were randomized to two groups: anodal or sham stimulation. For participants assigned to active stimulation, anodal stimulation of the left posterior parietal cortex was performed using 2 mA current for 20 min. Patients received anodal or sham stimulation, followed by motor practice in both groups. The primary outcome measure was time-performing sequential buttoning and unbuttoning, and several secondary outcome measures were obtained. A statistically significant interaction between stimulation type and timepoint on time taken to perform buttoning and unbuttoning was found. Patients who received anodal stimulation were found to have a significant decrease in sequential buttoning and unbuttoning time immediately following stimulation and at 24 h in the medication-ON state, compared to the medication-OFF state (31% and 29% decrease, respectively). Anodal stimulation of the left posterior parietal cortex prior to motor practice appears to be effective for limb-kinetic apraxia in Parkinson's disease. Future long-term, multi-session studies looking at the long-term effects of anodal stimulation and motor practice on limb-kinetic apraxia in Parkinson's disease may be worthwhile.

Development of an Antiwindup Technique for a Cascade Control System.

A cascade control system comprising the primary and secondary controllers suffers from a cascade-type integral windup problem in which the output saturation of the secondary control loop can considerably increase the integral part of the primary control loop. In this paper, we present a new predictive antiwindup technique that can completely eliminate the possibility of secondary controller output saturation, resulting in no cascade-type integral windup phenomenon. The proposed method does not require any type of process models; thus, its implementation is simple and straightforward, which is a very favorable advantage compared to the model-based antiwindup techniques from the practical viewpoint. Our simulation confirms that the proposed method can completely remove the primary controller's cascade-type integral windup resulting from the saturation of the secondary controller output. Further, the proposed method exhibited good control performance without needing any type of process model for the various types of processes and controllers. Our experimental study successfully demonstrated that there are no problems in applying the proposed method to real plants.