Using virtual reality simulation to study navigation in a complex environment as a functional-cognitive task; A pilot study.

BACKGROUND: Navigation skills are required for performance of functional complex tasks and may decline due to aging. Investigation of navigation skills should include measurement of cognitive-executive and motor aspects, which are part of complex tasks. OBJECTIVE: to compare young and older healthy adults in navigation within a simulated environment with and without a functional-cognitive task. METHODS: Ten young adults (25.6±4.3 years) and seven community dwelling older men (69.9±3.8 years) were tested during a single session. After training on a self-paced treadmill to navigate in a non-functional simulation, they performed the Virtual Multiple Errands Test (VMET) in a mall simulation. Outcome measures included cognitive-executive aspects of performance and gait parameters. RESULTS: Younger adults' performance of the VMET was more efficient (1.8±1.0) than older adults (5.3±2.7; p < 0.05) and faster (younger 478.1±141.5 s, older 867.6±393.5 s; p < 0.05). There were no differences between groups in gait parameters. Both groups walked slower in the mall simulation. CONCLUSIONS: The shopping simulation provided a paradigm to assess the interplay between motor and cognitive aspects involved in the efficient performance of a complex task. The study emphasized the role of the cognitive-executive aspect of task performance in healthy older adults.

Multi-frequency bioelectrical impedance analysis for assessing fat mass and fat-free mass in stroke or transient ischaemic attack patients.

BACKGROUND/OBJECTIVES: Dual energy X-ray absorptiometry (DEXA) is considered as the reference method in assessing fat-free and fat mass but is costly and not a pragmatic option in daily clinical practice. If devices based on multi-frequency bioelectrical impedance analysis (MF-BIA), which are cheaper and portable, are valid and reliable in measuring body composition, these could be used in routine clinical practice in nutritional management of patients and populations where malnutrition is prevalent. SUBJECTS/METHODS: A study of MF-BIA against DEXA in assessing fat-free and fat mass, and two internal validation studies of MF-BIA were conducted. Bland & Altman analysis to assess comparison against DEXA and Cronbach's α for internal validity were carried out. RESULTS: Ten participants (mean age 66 years; 70% men) with a recent stroke or transient ischaemic attack (TIA) were recruited to assess against DEXA and the first internal validation. The second internal validation was based on 80 pairs of MF-BIA measurements in 40 stroke patients (mean age 70.3 years; 55% men) assessed at hospital admission and on discharge. There was a strong correlation between MF-BIA and DEXA (correlation coefficient was 0.88 for fat-free mass and 0.77 for fat mass). According to Bland & Altman analysis, MF-BIA and DEXA fat-free and fat mass estimates were similar. Internal consistency was high with Cronbach's-α >0.9. CONCLUSION: MF-BIA can be reliably used in stroke and TIA patients. The feasibility, clinical and cost effectiveness of MF-BIA in routine monitoring and management of malnutrition in stroke and TIA patients with high prevalence of nutritional deficits is worthy of further evaluation.

Activation of selected frontal trunk and extremities muscles during rolling from supine to side lying in healthy subjects and in post-stroke hemiparetic patients.

The purpose of this work was to get insight into the role of frontal trunk and proximal extremity muscles in rolling from supine to side lying. Participants were seventeen hemiparetic patients and 14 healthy subjects. Electromyographic (EMG) activity of the Sternocleidomasoid (ScM), Pectoralis Major (PM), External Oblique (ExO) and Rectus Femoris (RF) muscle pairs was recorded during rolling performance. Analysis included the establishment of EMG response times and magnitudes. For all muscles, initiation of EMG activity was delayed in the patients as compared with the controls. Among the healthy subjects, EMG activity level of the SCM was more enhanced on the mobile than on the stable body side, while activation level of the PM muscle was larger on the stable body side. In the hemiparetic group, the SCM demonstrated similar results as the controls yet, PM activity on the paretic side was lower than on the non-paretic side regardless of rolling direction. The difference in activation level between the corresponding ExO and RF muscles showed inconsistency among the healthy subjects, whereas in the hemipareic group the muscles on the paretic side never displayed higher activation levels than on the non-paretic side. In conclusion, rolling sideways in hemiparetic subjects is characterized by a normal relationship between activation levels of the SCM muscles while the relationship between the corresponding PM, ExO and RF muscles is hampered due to reduced activation level of the muscles on the paretic body side.

High b-value q-space analyzed diffusion-weighted MRI: application to multiple sclerosis.

Multiple sclerosis (MS) is an inflammatory disease of the central nervous system (CNS) which affects nearly one million people worldwide, leading to a progressive decline of motor and sensory functions, and permanent disability. High b-value diffusion-weighted MR images (b of up to 14000 s/mm(2)) were acquired from the brains of controls and MS patients. These diffusion MR images, in which signal decay is not monoexponential, were analyzed using the q-space approach that emphasizes the diffusion characteristics of the slow-diffusing component. From this analysis, displacement and probability maps were constructed. The computed q-space analyzed MR images that were compared with conventional T(1), T(2) (fluid attenuated inversion recovery (FLAIR)), and diffusion tensor imaging (DTI) images were found to be sensitive to the pathophysiological state of white matter. The indices used to construct this q-space analyzed MR maps, provided a pronounced differentiation between normal tissue and tissues classified as MS plaques by the FLAIR images. More importantly, a pronounced differentiation was also observed between tissues classified by the FLAIR MR images as normal-appearing white matter (NAWM) in the MS brains, which are known to be abnormal, and the respective control tissues. The potential diagnostic capacity of high b-value diffusion q-space analyzed MR images is discussed, and experimental data that explains the consequences of using the q-space approach once the short pulse gradient approximation is violated are presented.

Autonomic dysfunction in experimental autoimmune neuritis: heart rate.

Autonomic nervous system (ANS) dysfunction occurs in more than half of Guillain--Barré syndrome (GBS) patients and is an important cause of death in the disease. In this study we examined heart rate (HR) changes in an animal model of GBS, experimental autoimmune neuritis (EAN), induced by immunization with myelin extracted from bovine spinal roots. The animals developed progressive motor weakness accompanied by significant weight loss and hypothermia. HR was measured in 33 EAN rats at rest (rHR) and followings stressful stimulation (sHR). Average pre-immunization rHR was 341+/-28 beats per minute (b.p.m.) and sHR was 486+/-21 bpm. Although the mean rHR in rats with EAN was not significantly different compared to that at baseline, there was a significant increase of variation of rHR with six rats demonstrating bradycardia (<280 b.p.m.) and 10 tachycardia (>400 b.p.m.) (P<0.01, F-test). sHR in EAN rats was significantly lower (P<0.01), suggesting sympathetic system impairment. These findings may serve as a basis for testing treatments of ANS dysfunction in EAN.