Brain activations underlying different patterns of performance improvement during early motor skill learning.

BACKGROUND/INTRODUCTION: Motor learning plays a central role in daily life and in neurorehabilitation. Several forms of motor learning have been described, among which motor skill learning, i.e. reaching a superior level of performance (a skill) through a shift of the speed/accuracy trade-off. During the first stage of learning a visuomotor skill, we observed differential patterns of evolution of the speed/accuracy trade-off in normal subjects. Half of the subjects rapidly achieved successful motor skill learning with an early shift of the speed/accuracy trade-off leading to a superior level of performance ("shift" pattern). The other subjects attained only minimal global improvement due to a converse evolution of speed and accuracy (i.e. a respect of the speed/accuracy trade-off: "fit" pattern). Functional magnetic resonance imaging (fMRI) was used to explore the neural substrates underlying these differential patterns during the first stage of motor skill learning in normal subjects. METHODS: Twenty right-handed normal subjects performed an implicit visuomotor learning task with their non-dominant hand. The task ("circuit game") consisted in learning to navigate a pointer along a circuit as quickly and accurately as possible using a fMRI-compatible mouse. Velocity, accuracy, and performance indexes were used to characterise the motor learning pattern (shift/fit) and to perform fMRI correlation analysis in order to find the neural substrate associated with the shift and fit patterns during early motor skill learning. RESULTS: Nine subjects showed a fit pattern ("fitters"), and eleven, a shift pattern ("shifters"). fMRI analyses at whole group level (ANOVA) and at sub-group level demonstrated that the supplementary motor area (SMA) was more activated in "shifters" than in the "fitters" groups and that the BOLD activation within the SMA correlated significantly with the on-line shift of the speed/accuracy trade-off in the "shifters" group. CONCLUSION: Despite identical instructions and experimental conditions, during the first stage of motor skill learning normal subjects spontaneously adopted different patterns that can be differentiated based on distinct fMRI activation patterns. In this implicit visuomotor task, the SMA proper was the key area underlying the achievement of early successful motor skill learning, i.e. on-line shift of the speed/accuracy trade-off

A manually controlled new device for punctuate mechanical stimulation of teeth during functional magnetic resonance imaging studies

P>Aim To design a simple and affordable device that could apply standardized mechanical punctuate stimuli to trigger the periodontal mechanoreceptors during functional magnetic resonance imaging (fMRI). Material and Methods A new manually controlled device using von Frey monofilaments was tested on a phantom and on eight volunteers. Four block design paradigms with different timing were compared. Teeth 11, 12, 13, 21, 22, 23 and the thumb were stimulated. Results The device did not induce any artefacts in MR images. The most efficient protocol included an epoch duration of 24 s and stimuli delivered at 1 Hz. When stimulating the teeth, activations of the primary (S1) and secondary (S2) somatosensory areas were consistently obtained, either on the ipsilateral, contra-lateral or both sides. Stimulation of the thumb led to activations of the contra-lateral S1 area and either ipsilateral or contra-lateral S2 area. Conclusion The use of this innovative tool should allow to perform fMRI studies aimed to unveil the neural correlates of periodontal neural receptors, and to understand their plasticity induced by tooth loss and their eventual replacement by endosseous oral implants

Analysis of prognostic factors in critically ill patients with COVID-19.

The Coronavirus Disease 2019 (COVID-19) has caused a global health crisis. Mortality predictors in critically ill patients remain under investigation. A retrospective cohort study included 201 patients admitted to the intensive care unit (ICU) due to COVID-19. Data on demographic characteristics, laboratory findings, and mortality were collected. Logistic regression analysis was conducted with various independent variables, including demographic characteristics, clinical factors, and treatment methods. The study aimed to identify key risk factors associated with mortality in an ICU. In an investigation of 201 patients comprising non-survivors (n = 80, 40%) and Survivors (n = 121, 60%), we identified several markers significantly associated with ICU mortality. Lower Interleukin 6 and White Blood Cells levels at both 24- and 48-hours post-ICU admission emerged as significant indicators of survival. The study employed logistic regression analysis to evaluate risk factors for in-ICU mortality. Analysis results revealed that demographic and clinical factors, including gender, age, and comorbidities, were not significant predictors of in-ICU mortality. Ventilator-associated pneumonia was significantly higher in Survivors, and the use of antibiotics showed a significant association with increased mortality risk in the multivariate model (OR: 11.2, p = 0.031). Our study underscores the significance of monitoring Il-6 and WBC levels within 48 hours of ICU admission, potentially influencing COVID-19 patient outcomes. These insights may reshape therapeutic strategies and ICU protocols for critically ill patients

White matter anatomy of the human deep brain revisited with high resolution DTI fibre tracking

Background and Purpose: Deep white matter (WM) fascicles play a major, yet poorly understood, role in the overall connectivity of human brain. Better knowledge of their anatomy is requisite to understand the clinical correlates of their lesions and develop targeted treatments. We investigated whether MR-based diffusion tensor imaging (DTI) and fibre tracking could reveal in vivo, in explicit details, the 3D WM architecture within the subthalamic region and the internal capsule. Methods: High-resolution DTI images were acquired on six healthy volunteers on a three Tesla MR scanner. We studied using single-subject analysis WM fascicles within the subthalamic region and the internal capsule, as follows: DTI deterministic fibre tracking (FT) of fascicles; embedding fascicles in the volume-rendered brain coupled with a triplanar view; rigorous anatomic labelling of each fascicle according to classical knowledge as described by pioneer neuroanatomists. Deterministic FT effects were taken into account. Results: We charted most of WM fascicles of the deep brain, in particular large and complex fascicles such as the basal forebrain bundle and the ansa lenticularis. A topographic classification of subthalamic fascicles was proposed into three groups: the cerebellorubral, the reticulo-dorsal and the tegmento-peripheral one. Conclusions: Beyond to demonstrate the feasibility of imaging the deepest WM fascicles in vivo, our results pave the way for a better understanding of the brain connectivity and for developing targeted neuromodulation. © 2011 Elsevier Masson SAS

Neural substrates underlying stimulation-enhanced motor skill learning after stroke.

Motor skill learning is one of the key components of motor function recovery after stroke, especially recovery driven by neurorehabilitation. Transcranial direct current stimulation can enhance neurorehabilitation and motor skill learning in stroke patients. However, the neural mechanisms underlying the retention of stimulation-enhanced motor skill learning involving a paretic upper limb have not been resolved. These neural substrates were explored by means of functional magnetic resonance imaging. Nineteen chronic hemiparetic stroke patients participated in a double-blind, cross-over randomized, sham-controlled experiment with two series. Each series consisted of two sessions: (i) an intervention session during which dual transcranial direct current stimulation or sham was applied during motor skill learning with the paretic upper limb; and (ii) an imaging session 1 week later, during which the patients performed the learned motor skill. The motor skill learning task, called the 'circuit game', involves a speed/accuracy trade-off and consists of moving a pointer controlled by a computer mouse along a complex circuit as quickly and accurately as possible. Relative to the sham series, dual transcranial direct current stimulation applied bilaterally over the primary motor cortex during motor skill learning with the paretic upper limb resulted in (i) enhanced online motor skill learning; (ii) enhanced 1-week retention; and (iii) superior transfer of performance improvement to an untrained task. The 1-week retention's enhancement driven by the intervention was associated with a trend towards normalization of the brain activation pattern during performance of the learned motor skill relative to the sham series. A similar trend towards normalization relative to sham was observed during performance of a simple, untrained task without a speed/accuracy constraint, despite a lack of behavioural difference between the dual transcranial direct current stimulation and sham series. Finally, dual transcranial direct current stimulation applied during the first session enhanced continued learning with the paretic limb 1 week later, relative to the sham series. This lasting behavioural enhancement was associated with more efficient recruitment of the motor skill learning network, that is, focused activation on the motor-premotor areas in the damaged hemisphere, especially on the dorsal premotor cortex. Dual transcranial direct current stimulation applied during motor skill learning with a paretic upper limb resulted in prolonged shaping of brain activation, which supported behavioural enhancements in stroke patients

Neural substrates underlying motor skill learning in chronic hemiparetic stroke patients

Motor skill learning is critical in post-stroke motor recovery, but little is known about its underlying neural substrates. Recently, using a new visuomotor skill learning paradigm involving a speed/accuracy trade-off in healthy individuals we identified three subpopulations based on their behavioral trajectories: fitters (in whom improvement in speed or accuracy coincided with deterioration in the other parameter), shifters (in whom speed and/or accuracy improved without degradation of the other parameter), and non-learners. We aimed to identify the neural substrates underlying the first stages of motor skill learning in chronic hemiparetic stroke patients and to determine whether specific neural substrates were recruited in shifters versus fitters. During functional magnetic resonance imaging (fMRI), 23 patients learned the visuomotor skill with their paretic upper limb. In the whole-group analysis, correlation between activation and motor skill learning was restricted to the dorsal prefrontal cortex of the damaged hemisphere (DLPFCdamh: r = -0.82) and the dorsal premotor cortex (PMddamh: r = 0.70); the correlations was much lesser (-0.16 0.25) in the other regions of interest. In a subgroup analysis, significant activation was restricted to bilateral posterior parietal cortices of the fitters and did not correlate with motor skill learning. Conversely, in shifters significant activation occurred in the primary sensorimotor cortexdamh and supplementary motor areadamh and in bilateral PMd where activation changes correlated significantly with motor skill learning (r = 0.91). Finally, resting-state activity acquired before learning showed a higher functional connectivity in the salience network of shifters compared with fitters (qFDR < 0.05). These data suggest a neuroplastic compensatory reorganization of brain activity underlying the first stages of motor skill learning with the paretic upper limb in chronic hemiparetic stroke patients, with a key role of bilateral PMd