Adaptive functional reorganization in amyotrophic lateral sclerosis: coexisting degenerative and compensatory changes.

BACKGROUND AND PURPOSE: Considerable functional reorganization takes place in amyotrophic lateral sclerosis (ALS) in face of relentless structural degeneration. This study evaluates functional adaptation in ALS patients with lower motor neuron predominant (LMNp) and upper motor neuron predominant (UMNp) dysfunction. METHODS: Seventeen LMNp ALS patients, 14 UMNp ALS patients and 14 controls participated in a functional magnetic resonance imaging study. Study-group-specific activation patterns were evaluated during preparation for a motor task. Connectivity analyses were carried out using the supplementary motor area (SMA), cerebellum and striatum as seed regions and correlations were explored with clinical measures. RESULTS: Increased cerebellar, decreased dorsolateral prefrontal cortex and decreased SMA activation were detected in UMNp patients compared to controls. Increased cerebellar activation was also detected in UMNp patients compared to LMNp patients. UMNp patients exhibit increased effective connectivity between the cerebellum and caudate, and decreased connectivity between the SMA and caudate and between the SMA and cerebellum when performing self-initiated movement. In UMNp patients, a positive correlation was detected between clinical variables and striato-cerebellar connectivity. CONCLUSIONS: Our findings indicate that, despite the dysfunction of SMA-striatal and SMA-cerebellar networks, cerebello-striatal connectivity increases in ALS indicative of compensatory processes. The coexistence of circuits with decreased and increased connectivity suggests concomitant neurodegenerative and adaptive changes in ALS.

How 100-m event analyses improve our understanding of world-class men's and women's sprint performance.

This study aimed to compare the force (F)-velocity (v)-power (P)-time (t) relationships of female and male world-class sprinters. A total of 100 distance-time curves (50 women and 50 men) were computed from international 100-m finals, to determine the acceleration and deceleration phases of each race: (a) mechanical variables describing the velocity, force, and power output; and (b) F-P-v relationships and associated maximal power output, theoretical force and velocity produced by each athlete (Pmax , F0 , and V0 ). The results showed that the maximal sprint velocity (Vmax ) and mean power output (W/kg) developed over the entire 100 m strongly influenced 100-m performance (r > -0.80; P ≤ 0.001). With the exception of mean force (N/kg) developed during the acceleration phase or during the entire 100 m, all of the mechanicals variables observed over the race were greater in men. Shorter acceleration and longer deceleration in women may explain both their lower Vmax and their greater decrease in velocity, and in turn their lower performance level, which can be explained by their higher V0 and its correlation with performance. This highlights the importance of the capability to keep applying horizontal force to the ground at high velocities.

Postural control anomalies in children with Tourette syndrome.

The goal of the present study was to determine whether postural control is affected in Gilles-de-la-Tourette syndrome (TS). Center of pressure (COP) displacements were recorded in children with TS and unaffected siblings in three conditions using a force platform: (1) Eyes-Open, (2) Eyes-Closed, (3) One-Leg standing with eyes open. The COP range and velocity were higher in children with TS than in unaffected siblings in all conditions. These differences could not be attributed to age, present tic severity, comorbidities (hyperactivity and compulsions) or medication. The data suggest that sub-clinical postural control anomalies are present in TS.

Postural control following a self-initiated reaching task in type 2 diabetic patients and age-matched controls.

Although the postural stability of diabetic patients is affected in the presence of polyneuropathy, it has been suggested that diabetes per se has no effect on balance control during quiet standing. However, recent studies have reported muscular mechanical deficits in patients with type 2 diabetes (T2D) that may be highlighted during a more destabilizing task than quiet standing. Therefore, the objective of this study was to compare non-diabetic and T2D subjects during a modified version of the functional reach (FR) test in order to discriminate differences in postural control associated with diabetes per se. Thirty subjects (15 non-diabetic and 15 T2D) were requested to stand on a force platform and to perform the FR test. Center of pressure velocity (V(COP)), root-mean-square (RMS) amplitude and range of the COP were calculated in the anterior-posterior direction during three specific periods of the FR performance: namely "before", "on-going" and "after". No significant difference between the non-diabetic subjects and the T2D subjects was found for the FR performance. However, T2D subjects had significantly higher V(COP), RMS and range of COP displacements for the "after" period compared to the non-diabetic group (p<0.05). These results suggest that T2D subjects without peripheral neuropathy may have difficulties regaining their stability after a self-initiated reaching task. Therefore, diabetes mellitus per se, could have a direct effect on postural control during standing after a self-induced forward reaching movement.