Program of Seven 45-min Dry Immersion Sessions Improves Choice Reaction Time in Parkinson’s Disease

The study hypothesis held that in subjects with Parkinson’s disease (PD), the reaction time (RT) tests of the higher cognition demand would have more readily improved under the program of analog microgravity (μG) modeled with “dry” immersion (DI). To test this hypothesis, 10 subjects with PD have passed through a program of seven DI sessions (each 45 min long) within 25–30 days, with overall μG dose 5 1/4 h. Five patients were enrolled as controls, without DI (noDI group). Simple RT (SRT), disjunctive RT (DRT), and choice RT (CRT) were assessed in four study points: before the DI program (preDI), 1 day after the DI program (postDI), 2 weeks after the DI program (DI2w), and 2 months after the DI program (DI2m). The motor time (MT) was assessed with the tapping test (TT). Additionally, signal detection time (SDT) and central processing time (CPT) were extracted from the data. Before the program of DI, the RT tests are in accordance with their cognition load: SRT (284 ± 37 ms), DRT (338 ± 38 ms), and CRT (540 ± 156 ms). In accordance with the hypothesis, CRT and DRT have improved under DI by, respectively, 20 and 8% at the study point “DI2w,” whereas SRT, SDT, and MT did not change (<5% in the preDI point, p > 0.05). Thus, the program of DI provoked RT improvement specifically in the cognitively loaded tasks, in a “dose of cognition-reaction” manner. The accuracy of reaction has changed in none of the RT tests. The neurophysiologic, hormonal/neuroendocrine, behavioral, neural plasticity, and acclimation mechanisms may have contributed to such a result.

Internal Model of Gravity for Hand Interception: Parametric Adaptation to Zero-Gravity Visual Targets on Earth

Internal model is a neural mechanism that mimics the dynamics of an object for sensory motor or cognitive functions. Recent research focuses on the issue of whether multiple internal models are learned and switched to cope with a variety of conditions, or single general models are adapted by tuning the parameters. Here we addressed this issue by investigating how the manual interception of a moving target changes with changes of the visual environment. In our paradigm, a virtual target moves vertically downward on a screen with different laws of motion. Subjects are asked to punch a hidden ball that arrives in synchrony with the visual target. By using several different protocols, we systematically found that subjects do not develop a new internal model appropriate for constant speed targets, but they use the default gravity model and reduce the central processing time. The results imply that adaptation to zero-gravity targets involves a compression of temporal processing through the cortical and subcortical regions interconnected with the vestibular cortex, which has previously been shown to be the site of storage of the internal model of gravity.

Timing and Torque Involvement in the Organisation of a Rapid Forearm Flexion

The study was designed to determine whether the magnitude of force and the timing of force are response parameters involved in the organisation of a rapid forearm flexion to a target. The magnitude of torque and the timing of torque were manipulated independently through manipulations of the total moment of inertia and movement time, and the effect of these manipulations on premotor and motor reaction times was observed. Planned comparison analyses revealed that premotor and motor reaction times increased when a movement, which required the same magnitude of torque as in a fast movement, was performed slower. However, premotor and motor reaction times were not affected when movements were performed at the same speed, but differed with respect to the magnitude of torque required. These results indicate that a different timing requirement in the forthcoming movement is associated with a corresponding change in the amount of central processing time required. Therefore, the timing of torque appears to be a parameter of the movement that is organised in advance of movement execution. However, a change in the specification for the magnitude of torque does not affect the amount of time needed to organise the movement.

Major Gene Locus of Spearman's General Factor of Intelligence

The reigning biometrical paradigm asserts that continuous variation implies the determination of intelligence by many genes with small effects. However, if an appreciable amount of the variability of a continuous trait is due to Mendelian segregation at a single locus, we may speak of the major locus for that trait. In such a case the distributions between the genotypic classes show considerable overlap, caused by error of measurement and environmental influences. As confirmed by Mendelian analysis, Spearman's general factor is the result of genotypes with discrete true scores of central processing time, the heterozygotes being exactly in the mean of the differences of the means of homozygotes.