The role of alpha oscillations in a premotor-cerebellar loop in modulation of motor learning: insights from transcranial alternating current stimulation

AbstractAlpha oscillations (8-13 Hz) have been shown to play an important role in dynamic neural processes underlying learning and memory. The goal of this study was to scrutinize the role of α oscillations in communication within a network implicated in motor sequence learning. To this end, we conducted two experiments using the serial reaction time task. In the first experiment, we explored changes in α power and cross-channel α coherence. We found a gradual decrease in learning-related α power over left premotor cortex (PMC), somatosensory cortex (S1) and tempo-parietal junction (TPJ). Alpha coherence between left PMC/S1 and right cerebellar crus I was reduced for sequence learning, possibly reflecting a functional decoupling in a motor-cerebellar loop during the motor learning process. In the second experiment in a different cohort, we applied 10Hz transcranial alternating current stimulation (tACS), a method shown to entrain local oscillatory activity, to left M1 (lM1) and right cerebellum (rCB) during sequence learning. We observed learning deficits during rCB tACS compared to sham, but not during lM1 tACS. In addition, learning-related α power following rCB tACS was increased in left PMC, possibly reflecting a decrease in neural activity. Importantly, learning-specific coherence between left PMC and right cerebellar lobule VIIb was enhanced following rCB tACS. These findings suggest that interactions within a premotor-cerebellar loop, which are underlying motor sequence learning, are mediated by α oscillations. We show that they can be modulated through external entrainment of cerebellar oscillations, which then modulates motor cortical α and interferes with sequence learning.</jats:p

No Harmful Effect of Endovascular Treatment before Decompressive Surgery&mdash;Implications for Handling Patients with Space-Occupying Brain Infarction

This study explored short- and mid-term functional outcomes in patients undergoing decompressive hemicraniectomy (DHC) due to space-occupying cerebral infarction and asked whether there is a potentially harmful effect of a priorly performed endovascular treatment (EVT). Medical records were screened for patients requiring DHC due to space-occupying cerebral infarction between January 2016 and July 2021. Functional outcomes at hospital discharge and at 3 months were assessed by the modified Rankin Scale (mRS). Out of 65 patients with DHC, 39 underwent EVT before DHC. Both groups, i.e., EVT + DHC and DHC alone, had similar volumes (280 &plusmn; 90 mL vs. 269 &plusmn; 73 mL, t-test, p = 0.633) and proportions of edema and infarction (22.1 &plusmn; 6.5% vs. 22.1 &plusmn; 6.1%, t-test, p = 0.989) before the surgical intervention. Patients undergoing EVT + DHC tended to have a better functional outcome at hospital discharge compared to DHC alone (mRS 4.8 &plusmn; 0.8 vs. 5.2 &plusmn; 0.7, Mann&ndash;Whitney-U, p = 0.061), while the functional outcome after 3 months was similar (mRS 4.6 &plusmn; 1.1 vs. 4.8 &plusmn; 0.9, Mann&ndash;Whitney-U, p = 0.352). In patients initially presenting with a relevant infarct demarcation (Alberta Stroke Program Early CT Score &le; 5), the outcome was similar at hospital discharge and after 3 months between patients with EVT + DHC and DHC alone. This study provided no evidence for a harmful effect of EVT before DHC in patients with space-occupying brain infarction

Frequency and treatment of venous thromboembolic events in patients with space-occupying brain infarction and decompressive craniectomy

Introduction Venous thromboembolic events (VTEs) like deep vein thrombosis or pulmonary embolism are frequent complications in (neuro) critical ill patients. Anticoagulation for VTE after space-occupying brain infarction is a therapeutic dilemma. The aim of this retrospective study was to investigate the frequency of clinically apparent VTE in patients with acute ischaemic stroke (AIS) due to large vessel occlusion (LVO), its treatment, and the rate of complications.Methods Patients with first AIS due to LVO were assigned to one of the following groups: space-occupying brain infarction with (1) or without (2) decompressive craniectomy (DC), AIS comprising more than 2/3 (3) or less than 2/3 (4) of the middle cerebral artery territory. Clinically obtained parameters included risk factors for VTE, type of thromboprophylaxis, treatment of VTE and treatment-associated complications.Results 15 of 173 (8.7%) patients had a VTE, which was diagnosed 10.9 ± 7.2 days after admission. Patients with a space-occupying brain infarction and DC had significantly more VTE (n=11/63; 17.5%) than patients with a space-occupying brain infarction without DC (0/26; p =0.023) or patients without DC (4/110; 3.6%; p = 0.004). Younger age, DC and cumulative duration of central venous catheter were identified as risk factors for VTE. Only three patients had major bleeding events while being anticoagulated (one asymptomatic cerebral and two extracranial bleedings).Discussion Patients with space-occupying brain infarction and DC hold a high risk for VTE. Despite extensive infarct size and DC, therapeutic anticoagulation required for VTE appeared to be safe regarding intracranial bleeding complications