Spinal cord dysfunction contributes to balance impairment in multiple sclerosis patients.

OBJECTIVES: Balance impairment is very common in multiple sclerosis (MS) but its causes are still unclear. Some studies suggest that balance deficit originates mainly from damage in specific locations of the central nervous system such as cerebellum and spinal cord, that are involved in transmission and integration of sensory inputs and motor outputs. The aim of this study is to investigate the contribution of spinal cord to MS-related imbalance, by combining neurophysiologic and neuroimaging techniques. PATIENTS AND METHODS: Balance performance was correlated with clinical, neurophysiological and MRI findings. The functionality of spinal cord was tested by somatosensory (SEP) and motor (MEP) evoked potentials. MRI was used to identify spinal and cerebellar lesions. Balance performance was assessed by Tinetti Scale (TS). Clinical disability was measured by EDSS. RESULTS: 38 patients were included. Linear regression model revealed significant negative correlations between TS and EDSS scores, between TS and cervical lesions, and between TS and SEP findings. CONCLUSION: Our study, by combining neurophysiologic and neuroimaging techniques, confirms that spinal cord plays an important role for balance control and that its dysfunction, especially in lower limbs somatosensory ascending pathways conveying proprioceptive information, contributes to balance impairment in MS patients.

Linking cognitive abilities with the propensity for risk-taking: the balloon analogue risk task.

There is great interest about the individual differences that influence the ability of dealing with risky decisions. In this light, an intriguing question is whether decision-making during risk is related to other cognitive abilities, especially executive functions. To investigate, in healthy subjects, the existence of a possible correlation between risk-taking and cognitive abilities, the balloon analogue risk task (BART) has been exploited to assess risk-taking propensity and the random number generation (RNG), to investigate cognitive functions. The risk-taking propensity is significantly correlated with the Cycling factor, a feature of RNG performance specifically related to the ability of updating and monitoring information. In particular, an excessive activity of monitoring (expressed by lower values of Cycling factor) is related to a more risk-averse behavior. An overlapping between the circuits involved in both RNG and BART, centered on the dorsolateral prefrontal cortex, could be the possible neurophysiological substrate for this correlation. This study suggests a relevant contribution of executive functions in risk-taking behavior. This could have relevant implications in neuroeconomics and neuropsychiatry of addiction and pathological gambling.

The effect of practice on random number generation task: a transcranial direct current stimulation study.

Random number generation (RNG) is a procedurally-simple task related to specific executive functions, such as updating and monitoring of information and inhibition of automatic responses. The effect of practice on executive functions has been widely investigated, however little is known on the impact of practice on RNG. Transcranial direct current stimulation (tDCS) allows to modulate, non-invasively, brain activity and to enhance the effects of training on executive functions. Hence, this study aims to investigate the effect of practice on RNG and to explore the possibility to influence it by tDCS applied over dorsolateral prefrontal cortex. Twenty-six healthy volunteers have been evaluated within single session and between different sessions of RNG using several measures of randomness, which are informative of separable cognitive components servicing random behavior. We found that repetition measures significantly change within single session, seriation measures significantly change both within and between sessions, while cycling measures are not affected by practice. tDCS does not produce any additional effect, however a sub-analysis limited to the first session revealed an increasing trend in seriation measure after anodal compared to cathodal stimulation. Our findings support the hypothesis that practice selectively and consistently influences specific cognitive components related to random behavior, while tDCS transiently affects RNG performance.