Modulation of ipsilateral motor evoked potentials during bimanual coordination tasks

IntroductionIpsilateral motor evoked potentials (iMEPs) are difficult to obtain in distal upper limb muscles of healthy participants but give a direct insight into the role of ipsilateral motor control.MethodsWe tested a new high-intensity double pulse transcranial magnetic stimulation (TMS) protocol to elicit iMEPs in wrist extensor and flexor muscles during four different bimanual movements (cooperative—asymmetric, cooperative—symmetric, non-cooperative—asymmetric and non-cooperative—symmetric) in 16 participants.ResultsNine participants showed an iMEP in the wrist extensor in at least 20% of the trials in each of the conditions and were classified as iMEP+ participants. iMEP persistence was greater for cooperative (50.5 ± 28.8%) compared to non-cooperative (31.6 ± 22.1%) tasks but did not differ between asymmetric and symmetric tasks. Area and amplitude of iMEPs were also increased during cooperative (area = 5.41 ± 3.4 mV × ms; amplitude = 1.60 ± 1.09 mV) compared to non-cooperative (area = 3.89 ± 2.0 mV × ms; amplitude = 1.12 ± 0.56 mV) tasks and unaffected by task-symmetry.DiscussionThe upregulation of iMEPs during common-goal cooperative tasks shows a functional relevance of ipsilateral motor control in bimanual movements. The paired-pulse TMS protocol is a reliable method to elicit iMEPs in healthy participants and can give new information about neural control of upper limb movements. With this work we contribute to the research field in two main aspects. First, we describe a reliable method to elicit ipsilateral motor evoked potentials in healthy participants which will be useful in further advancing research in the area of upper limb movements. Second, we add new insight into the motor control of bimanual movements. We were able to show an upregulation of bilateral control represented by increased ipsilateral motor evoked potentials in cooperative, object-oriented movements compared to separate bimanual tasks. This result might also have an impact on neurorehabilitation after stroke

Proactive modulation of long-interval intracortical inhibition during response inhibition

Daily activities often require sudden cancellation of preplanned movement, termed response inhibition. When only a subcomponent of a whole response must be suppressed (required here on Partial trials), the ensuing component is markedly delayed. The neural mechanisms underlying partial response inhibition remain unclear. We hypothesized that Partial trials would be associated with nonselective corticomotor suppression and that GABA(B) receptor-mediated inhibition within primary motor cortex might be responsible for the nonselective corticomotor suppression contributing to Partial trial response delays. Sixteen right-handed participants performed a bimanual anticipatory response inhibition task while single- and paired-pulse transcranial magnetic stimulation was delivered to elicit motor evoked potentials in the left first dorsal interosseous muscle. Lift times, amplitude of motor evoked potentials, and long-interval intracortical inhibition were examined across the different trial types (Go, Stop-Left, Stop-Right, Stop-Both). Go trials produced a tight distribution of lift times around the target, whereas those during Partial trials (Stop-Left and Stop-Right) were substantially delayed. The modulation of motor evoked potential amplitude during Stop-Right trials reflected anticipation, suppression, and subsequent reinitiation of movement. Importantly, suppression was present across all Stop trial types, indicative of a “default” nonselective inhibitory process. Compared with blocks containing only Go trials, inhibition increased when Stop trials were introduced but did not differ between trial types. The amount of inhibition was positively correlated with lift times during Stop-Right trials. Tonic levels of inhibition appear to be proactively modulated by task context and influence the speed at which unimanual responses occur after a nonselective “brake” is applied

Lymphoproliferation und Antigenspezifität von Lymphozyten frisch manifestierter Typ I Diabetiker gegen die Proteine Bovines Serum Albumin und Beta-Casein sowie Insulin

Ziel dier Arbeit war der Nachweis T-Lymphozyten, die spezifisch auf in der Nahrung vorkommende bzw. körpereigene Antigene reagieren, sowie die Bildung antigenspezifischer T-Zelllinien.Es wurde dabei untersucht, ob Unterschiede in Lyphoproliferation und Antigenspezifität zwischen frisch manifestierten Typ I Diabetikern sowie gesunden Kontrollpersonen nachweisbar sind.Nach der Isolation von Lymphozyten aus dem peripher venösen Blut der Probanden erfolgte die Kultivierung der Zellen mit den verschiedenen Antigenen sowie Tetanol als Kontrolle. Es folgten 5-7 Stimulationen mit Interleukin-2, im Anschluß daran der Test auf antigenspezifische Proliferation. Dabei wurden die Zellen der generierten Linien erneut mit ihren jeweiligen Antigenen kultiviert, nach 56 h radioaktiv markiert und nach 72 h geerntet. Die intrazelluläre Radioaktivität wurde gemessen, und galt als ein Maß für die Proliferationsaktivität der Zellen. Weiterhin wurde ein Proliferationsindex gebildet als Maß für die antigenspezifische Proliferation.Beim Vergleich zwischen den Gruppen ergaben sich keine signifikannten Unterschiede. Typ I Diabetiker wiesen tendeziell die höhere Lymphoproliferatin auf.The aim of this study was T-lymphocytes, specific for cow´s milk antigens and insulin, and the generation of antigen specific T-cellines.Furhtermore was tried to give evidence for differences in lymphoproliferation and antigen specificity between newly diagnosed patients with type I diabetes and healthy controls.After isolation of lymphocytes from peripheral blood, they were cocultered with the investigated antigens BSA, Casein and insulin, tetanol was used as control; followed by 5-7 stimulations with interleukin-2.After this generation of T-cellines the test for antigen specific proliferation was assesed.The generated t-cells were cultured again with the specific antigen, marked with a radioactive amino acid, and harvested after 72 h. The incorporated radioactivity was the expression for lymphoproliferation. To determine antigen specific proliferation the proliferation index was developed.The results of the tested groups were compared. No significant differebces were found. Type I diabetic patinets seem to express higher activity of T-lymphocytes

PREP2 Algorithm Predictions Are Correct at 2 Years Poststroke for Most Patients

Background. The PREP2 algorithm combines clinical and neurophysiological measures to predict upper-limb (UL) motor outcomes 3 months poststroke, using 4 prediction categories based on Action Research Arm Test (ARAT) scores. The algorithm was accurate at 3 months for 75% of participants in a previous validation study. Objective. This study aimed to evaluate whether PREP2 predictions made at baseline are correct 2 years poststroke. We also assessed whether patients’ UL performance remained stable, improved, or worsened between 3 months and 2 years after stroke. Methods. This is a follow-up study of 192 participants recruited and assessed in the original PREP2 validation study. Participants who completed assessments 3 months poststroke (n = 157) were invited to complete follow-up assessments at 2 years poststroke for the present study. UL outcomes were assessed with the ARAT, upper extremity Fugl-Meyer Scale, and Motor Activity Log. Results. A total of 86 participants completed 2-year follow-up assessments in this study. PREP2 predictions made at baseline were correct for 69/86 (80%) participants 2 years poststroke, and PREP2 UL outcome category was stable between 3 months and 2 years poststroke for 71/86 (83%). There was no difference in age, stroke severity, or comorbidities among patients whose category remained stable, improved, or deteriorated. Conclusions. PREP2 algorithm predictions made within days of stroke are correct at both 3 months and 2 years poststroke for most patients. Further investigation may be useful to identify which patients are likely to improve, remain stable, or deteriorate between 3 months and 2 years

Arguments for the biological and predictive relevance of the proportional recovery rule

The proportional recovery rule (PRR) posits that most stroke survivors can expect to reduce a fixed proportion of their motor impairment. As a statistical model, the PRR explicitly relates change scores to baseline values - an approach that arises in many scientific domains but has the potential to introduce artifacts and flawed conclusions. We describe approaches that can assess associations between baseline and changes from baseline while avoiding artifacts due either to mathematical coupling or to regression to the mean. We also describe methods that can compare different biological models of recovery. Across several real datasets in stroke recovery, we find evidence for non-artifactual associations between baseline and change, and support for the PRR compared to alternative models. We also introduce a statistical perspective that can be used to assess future models. We conclude that the PRR remains a biologically relevant model of stroke recovery