Effects of a single mental chronometry training session in subacute stroke patients - a randomized controlled trial

Background

Motor imagery training might be helpful in stroke rehabilitation. This study explored if a single session of motor imagery (MI) training induces performance changes in mental chronometry (MC), motor execution, or changes of motor excitability.

Methods

Subacute stroke patients (n = 33) participated in two training sessions. The order was randomized. One training consisted of a mental chronometry task, the other training was a hand identification task, each lasting 30 min. Before and after the training session, the Box and Block Test (BBT) was fully executed and also performed as a mental version which served as a measure of MC. A subgroup analysis based on the presence of sensory deficits was performed. Patients were allocated to three groups (no sensory deficits, moderate sensory deficits, severe sensory deficits). Motor excitability was measured by transcranial magnetic stimulation (TMS) pre and post training. Amplitudes of motor evoked potentials at rest and during pre-innervation as well as the duration of cortical silent period were measured in the affected and the non-affected hand.

Results

Pre-post differences of MC showed an improved MC after the MI training, whereas MC was worse after the hand identification training. Motor execution of the BBT was significantly improved after mental chronometry training but not after hand identification task training. Patients with severe sensory deficits performed significantly inferior in BBT execution and MC abilities prior to the training session compared to patients without sensory deficits or with moderate sensory deficits. However, pre-post differences of MC were similar in the 3 groups. TMS results were not different between pre and post training but showed significant differences between affected and unaffected side.

Conclusion

Even a single training session can modulate MC abilities and BBT motor execution in a task-specific way. Severe sensory deficits are associated with poorer motor performance and poorer MC ability, but do not have a negative impact on training-associated changes of mental chronometry. Studies with longer treatment periods should explore if the observed changes can further be expanded.

Trial registration

DRKS, DRKS00020355, registered March 9th, 2020, retrospectively registered

Using an upper extremity exoskeleton for semi-autonomous exercise during inpatient neurological rehabilitation- a pilot study

Background

Motor deficits are the most common symptoms after stroke. There is some evidence that intensity and amount of exercises influence the degree of improvement of functions within the first 6 months after the injury.

The purpose of this pilot study was to evaluate the feasibility and acceptance of semi-autonomous exercises with an upper extremity exoskeleton in addition to an inpatient rehabilitation program. In addition, changes of motor functions were examined.

Methods

Ten stroke patients with a severe upper extremity paresis were included. They were offered to perform a semi-autonomous training with a gravity-supported, computer-enhanced device (Armeo®Spring, Hocoma AG) six times per week for 4 weeks. Feasibility was evaluated by weekly structured interviews with patients and supervisors.

Motor functions were assessed before and after the training period using the Wolf Motor Function Test (WMFT). The Wilcoxon Signed Rank Test was used for assessing pre-post differences. The Pearson correlation co-efficient was used for correlating the number of completed sessions with the change in motor function. Acceptance of the device and the level of satisfaction with the training were determined by a questionnaire based on visual analogue scales.

Results

Neither patients nor supervisors reported side effects. However, one patient had to be excluded from analysis because of transportation difficulties from the ward to the treatment facility. Therefore, analysis was based on nine patients. On average, 13.2 (55%) sessions were realized. WMFT results showed significant improvements of proximal arm functions. The number of sessions correlated with the degree of shoulder force improvement. Patients rated the exercises to be motivating, and enjoyable and would continue using the Armeo®Spring at home if they had the opportunity.

Conclusion

Using an upper extremity exoskeleton for semi-autonomous training in an inpatient setting is feasible without side effects and is positively rated by the patients. It might further support the recovery of upper extremity function.

Trial registration

The trial was retrospectively registered. Registration number ISRCTN42633681.

Motor Imagery Impairment in Postacute Stroke Patients

Not much is known about how well stroke patients are able to perform motor imagery (MI) and which MI abilities are preserved after stroke. We therefore applied three different MI tasks (one mental chronometry task, one mental rotation task, and one EEG-based neurofeedback task) to a sample of postacute stroke patients (n = 20) and age-matched healthy controls (n = 20) for addressing the following questions: First, which of the MI tasks indicate impairment in stroke patients and are impairments restricted to the paretic side? Second, is there a relationship between MI impairment and sensory loss or paresis severity? And third, do the results of the different MI tasks converge? Significant differences between the stroke and control groups were found in all three MI tasks. However, only the mental chronometry task and EEG analysis revealed paresis side-specific effects. Moreover, sensitivity loss contributed to a performance drop in the mental rotation task. The findings indicate that although MI abilities may be impaired after stroke, most patients retain their ability for MI EEG-based neurofeedback. Interestingly, performance in the different MI measures did not strongly correlate, neither in stroke patients nor in healthy controls. We conclude that one MI measure is not sufficient to fully assess an individual's MI abilities.

[Neurofeedback-based motor imagery training for rehabilitation after stroke]

Mental training, including motor observation and motor imagery, has awakened much academic interest. The presumed functional equivalence of motor imagery and motor execution has given hope that mental training could be used for motor rehabilitation after a stroke. Results obtained from randomized controlled trials have shown mixed results. Approximately half of the studies demonstrate positive effects of motor imagery training but the rest do not show an additional benefit. Possible reasons why motor imagery training has so far not become established as a robust therapeutic approach are discussed in detail. Moreover, more recent approaches, such as neurofeedback-based motor imagery or closed-loop systems are presented and the potential importance for motor learning and rehabilitation after a stroke is discussed.

Mental chronometry and mental rotation abilities in stroke patients with different degrees of sensory deficit

BACKGROUND

Motor imagery is used for treatment of motor deficits after stroke. Clinical observations suggested that motor imagery abilities might be reduced in patients with severe sensory deficits. This study investigated the influence of somatosensory deficits on temporal (mental chronometry, MC) and spatial aspects of motor imagery abilities.

METHODS

Stroke patients (n = 70; <6 months after stroke) were subdivided into 3 groups according to their somatosensory functions. Group 1 (n = 31) had no sensory deficits, group 2 (n = 27) had a mild to moderate sensory impairment and group 3 (n = 12) had severe sensory deficits. Patients and a healthy age-matched control group (n = 23) participated in a mental chronometry task (Box and Block Test, BBT) and a mental rotation task (Hand Identification Test, HIT). MC abilities were expressed as a ratio (motor execution time-motor imagery time/motor execution time).

RESULTS

MC for the affected hand was significantly impaired in group 3 in comparison to stroke patients of group 1 (p = 0.006), group 2 (p = 0.005) and healthy controls (p < 0.001). For the non-affected hand MC was similar across all groups. Stroke patients had a slower BBT motor execution than healthy controls (p < 0.001), and group 1 executed the task faster than group 3 (p = 0.002). The percentage of correct responses in the HIT was similar for all groups.

CONCLUSION

Severe sensory deficits impair mental chronometry abilities but have no impact on mental rotation abilities. Future studies should explore whether the presence of severe sensory deficits in stroke patients reduces the benefit from motor imagery therapy.

Temporary deafferentation evoked by cutaneous anesthesia: behavioral and electrophysiological findings in healthy subjects

Motor function and motor excitability can be modulated by changes of somatosensory input. Here, we performed a randomized single-blind trial to investigate behavioral and neurophysiological changes during temporary deafferentation of left upper arm and forearm in 31 right-handed healthy adults. Lidocaine cream was used to anesthetize the skin from wrist to shoulder, sparing the hand. As control condition, on a different day, a neutral cream was applied to the same skin area. The sequence (first Lidocaine, then placebo or vice versa) was randomized. Behavioral measures included the Grating Orientation Task, the Von Frey hair testing and the Nine-hole-peg-test. Transcranial magnetic stimulation was used to investigate short-interval intracortical inhibition, stimulus response curves, motor evoked potential amplitudes during pre-innervation and the cortical silent period (CSP). Recordings were obtained from left first dorsal interosseous muscle and from left flexor carpi radialis muscle. During deafferentation, the threshold of touch measured at the forearm was significantly worse. Other behavioral treatment-related changes were not found. The CSP showed a significant interaction between treatment and time in first dorsal interosseous muscle. CSP duration was longer during Lidocaine application and shorter during placebo exposure. We conclude that, in healthy subjects, temporary cutaneous deafferentation of upper and lower arm may have minor effects on motor inhibition, but not on sensory or motor function for the adjacent non-anesthetized hand.

Search for a dark matter annihilation signal from the galactic center halo with H.E.S.S

A search for a very-high-energy (VHE; ≥100  GeV) γ-ray signal from self-annihilating particle dark matter (DM) is performed towards a region of projected distance r∼45-150  pc from the Galactic center. The background-subtracted γ-ray spectrum measured with the High Energy Stereoscopic System (H.E.S.S.) γ-ray instrument in the energy range between 300 GeV and 30 TeV shows no hint of a residual γ-ray flux. Assuming conventional Navarro-Frenk-White and Einasto density profiles, limits are derived on the velocity-weighted annihilation cross section (σv) as a function of the DM particle mass. These are among the best reported so far for this energy range and in particular differ only little between the chosen density profile parametrizations. In particular, for the DM particle mass of ∼1  TeV, values for (σv) above 3×10(-25)  cm(3) s(-1) are excluded for the Einasto density profile.

Energy spectrum of cosmic-ray electrons at TeV energies

The very large collection area of ground-based gamma-ray telescopes gives them a substantial advantage over balloon or satellite based instruments in the detection of very-high-energy (>600 GeV) cosmic-ray electrons. Here we present the electron spectrum derived from data taken with the High Energy Stereoscopic System (H.E.S.S.) of imaging atmospheric Cherenkov telescopes. In this measurement, the first of this type, we are able to extend the measurement of the electron spectrum beyond the range accessible to direct measurements. We find evidence for a substantial steepening in the energy spectrum above 600 GeV compared to lower energies.

Limits on an energy dependence of the speed of light from a flare of the active galaxy PKS 2155-304

In the past few decades, several models have predicted an energy dependence of the speed of light in the context of quantum gravity. For cosmological sources such as active galaxies, this minuscule effect can add up to measurable photon-energy dependent time lags. In this Letter a search for such time lags during the High Energy Stereoscopic System observations of the exceptional very high energy flare of the active galaxy PKS 2155-304 on 28 July 2006 is presented. Since no significant time lag is found, lower limits on the energy scale of speed of light modifications are derived.

HESS observations of the galactic center region and their possible dark matter interpretation

The detection of gamma rays from the source HESS J1745-290 in the Galactic Center (GC) region with the High Energy Spectroscopic System (HESS) array of Cherenkov telescopes in 2004 is presented. After subtraction of the diffuse gamma-ray emission from the GC ridge, the source is compatible with a point source with spatial extent less than 1.2;{'}(stat) (95% C.L.). The measured energy spectrum above 160 GeV is compatible with a power law with photon index of 2.25+/-0.04(stat)+/-0.10(syst) and no significant flux variation is detected. It is finally found that the bulk of the very high energy emission must have non-dark-matter origin.

Syntheses and properties of zinc and calcium complexes of valinate and isovalinate: metal alpha-amino acidates as possible constituents of the early Earth's chemical inventory

We have studied the ligand behavior of racemic isovalinate (iva) and valinate (val) towards zinc(II) and calcium(II). The following solid metal amino acidates were obtained from aqueous solutions: Zn3Cl2(iva)4 (1), Zn3Cl2(val)4 (2). Zn(val)2 (3), Zn(iva)2 x 2H2O (4), Zn(iva)2 x 3.25H2O (5), Zn(iva)2 (6), Ca(iva)2x xH2O (7), and Ca(val)2 x H2O (8). Except for complex 3, these were hitherto unknown compounds. The conditions under which they formed, together with current ideas of the conditions on early Earth, support the assumption that alpha-amino acidate complexes of zinc and calcium might have belonged to early Earth's prebiotic chemical inventory. The zinc isovalinates 1, 4, and 5 were characterized by X-ray crystal structure analyses. Complex 1 forms a layer structure containing four- and five-coordinate metal atoms, whereas the zinc atoms in 4 and 5 are five-coordinate. Compound 5 possesses an unprecedented nonpolymeric structure built from cyclic [Zn6(iva)12] complexes, which are separated by water molecules. The thermolyses of solids 1. 3, and 8 at 320 degrees C in an N2 atmosphere yielded numerous organic products, including the cyclic dipeptide of valine from 3 and 8. Condensation, C-C bond breaking and bond formation, aromatization, decarboxylation, and deamination reactions occurred during the thermolyses. Such reactions of metal-bound a-amino acidates that are abiotically formed could already have contributed to an organic-geochemical diversity before life appeared on Earth.