Prefrontal Cortex and Supplementary Motor Area Activation During Robot-Assisted Weight-Supported Over-Ground Walking in Young Neurological Patients: A Pilot fNIRS Study

Introduction: Rehabilitation therapy devices are designed for practicing intensively task-specific exercises inducing long-term neuroplastic changes underlying improved functional outcome. The Andago enables over-ground walking with bodyweight support requiring relatively high cognitive demands. In this study, we investigated whether we could identify children and adolescents with neurological gait impairments who show increased hemodynamic responses of the supplementary motor area (SMA) or prefrontal cortex (PFC) measured with functional near-infrared spectroscopy (fNIRS) when walking in Andago compared to walking on a treadmill. We further assessed the practicability and acceptability of fNIRS.Methods: Thirteen participants (two girls, 11 boys, age 8.0–15.7 years) with neurological impairments walked in the Andago and on a treadmill under comparable conditions. We measured hemodynamic responses over SMA and PFC during 10 walks (each lasting 20 s.) per condition and analyzed the data according to the latest recommendations. In addition, we listed technical issues, stopped the time needed to don fNIRS, and used a questionnaire to assess acceptability.Results: Hemodynamic responses varied largely between participants. Participants with a typical hemodynamic response (i.e., increased oxygenated hemoglobin concentration) showed large cortical activations during walking in Andago compared to treadmill walking (large effect sizes, i.e., for SMA: r = 0.91, n = 4; for PFC: r = 0.62, n = 3). Other participants showed atypical (SMA: n = 2; PFC: n = 4) or inconclusive hemodynamic responses (SMA: n = 5; PFC: n = 4). The median time for donning fNIRS was 28 min. The questionnaire indicated high acceptance of fNIRS, despite that single participants reported painful sensations.Discussion: Repetitive increased activation of cortical areas like the SMA and PFC might result in long-term neuroplastic changes underlying improved functional outcome. This cross-sectional pilot study provides first numbers on hemodynamic responses in SMA and PFC during walking in Andago in children with neurological impairments, reveals that only a small proportion of the participants shows typical hemodynamic responses, and reports that fNIRS requires considerable time for donning. This information is needed when designing future longitudinal studies to investigate whether increased brain activation of SMA and PFC during walking in Andago could serve as a biomarker to identify potential therapy responders among children and adolescents undergoing neurorehabilitation.

Word structure tunes electrophysiological and hemodynamic responses in the frontal cortex

As a morphological impoverished language, how does word structure impact Chinese lexical processing in the brain? To address this issue, the current study examined the temporal signatures and localizations in the human brain for morphological priming effect (compound/derivation constitute priming vs. non-morphological priming) and word structure modulation (derivation vs. compound) in light of EEG-fNIRS fusion. Whilst morphological priming effect was manifested in behavioral performance and left prefrontal hemodynamic responses, word structure effect was prominent drawing on behavioral, ERP, and fNIRS data. Chinese derivations elicited greater activation in the frontal cortex and engaged more distributed network than lexicalized compounds. The results were interpreted by the differing connection patterns between constitute morphemes within a given word structure from spreading activation perspective. Together, Chinese word structure effect showed a distinct pattern from the dual-route mechanism in alphabetic languages. Meanwhile, the current study for the first time identified dissociable behavioral and neurophysiological responses of Chinese derivations and coordinate compounds.

Renal Denervation in Combination With Angiotensin Receptor Blockade Prolongs Blood Pressure Trough During Hemorrhage

Majority of patients with hypertension and chronic kidney disease (CKD) undergoing renal denervation (RDN) are maintained on antihypertensive medication. However, RDN may impair compensatory responses to hypotension induced by blood loss. Therefore, continuation of antihypertensive medications in denervated patients may exacerbate hypotensive episodes. This study examined whether antihypertensive medication compromised hemodynamic responses to blood loss in normotensive (control) sheep and in sheep with hypertensive CKD at 30 months after RDN (control-RDN, CKD-RDN) or sham (control-intact, CKD-intact) procedure. CKD-RDN sheep had lower basal blood pressure (BP; ≈9 mm Hg) and higher basal renal blood flow (≈38%) than CKD-intact. Candesartan lowered BP and increased renal blood flow in all groups. 10% loss of blood volume alone caused a modest fall in BP (≈6–8 mm Hg) in all groups but did not affect the recovery of BP. 10% loss of blood volume in the presence of candesartan prolonged the time at trough BP by 9 minutes and attenuated the fall in renal blood flow in the CKD-RDN group compared with CKD-intact. Candesartan in combination with RDN prolonged trough BP and attenuated renal hemodynamic responses to blood loss. To minimize the risk of hypotension-mediated organ damage, patients with RDN maintained on antihypertensive medications may require closer monitoring when undergoing surgery or experiencing traumatic blood loss.

Effects of Dexmedetomidine on Intraoperative Hemodynamic Responses in Patients Undergoing Laparoscopic Cholecystectomy: A Randomised Double Blind Trial

Background: Dexmedetomidine is selective alpha 2 agonist with sedative sympatholytic, analgesic properties and is used as an anaesthetic adjuvant. We have evaluated the effect of dexmedetomidine on various hemodynamic responses to incidences such as laryngoscopy, endotracheal intubation, exubation and pneumoperitoneum in patients who were undergoing surgeries like laparoscopic cholecystectomy. We have used loading dose of 0.5mcg/kg of inj. Dexmedetomidine given over 10 minutes followed by infusion of a dose of 0.3mcg/kg/hour for the control of hemodynamic response to laparoscopy. Methods: Patient of either sex aged between 18-50 yrs, belongs to ASA I and II (AMERICAN SOCIETY OF ANAESTHESIOLOGY) posted for laparoscopic cholecystectomy were included. Institutional ethical committee clearance was obtained prior to study. After enrolment and valid written consent was taken. 60 patients were enrolled written valid informed consent was taken. Patients were divided into two groups 30 each with computerized randomization. Base line parameters were noted. Observer and patient was blinded for the content of syringe. Group A received injection dexmedetomidine and group B received bolus and infusion of normal saline at same rate. Routine general anaesthesia was instituted. Parameters were noted after induction, after intubation, after co2 insufflation, after 20 min, after 40 min, after co2 deflation, after extubation, after 1 and 2 hrs post-extubation. Results: Group A showed significantly less rise in HR and MAP than Group B. Requirement of intraoperative propofol was more in Group B. There was no significant difference for time taken to awakening in both groups. Conclusion: We found Injection Dexmedetomidine in given doses gave good hemodynamic control with minimal undesired effects during laparoscopy.

Hierarchical Bayesian Modeling of the Relationship between Task Related Hemodynamic Responses and Neuronal Excitability: a Simultaneous fNIRS/TMS Study

Background: Investigating the relationship between task-related cortical hemodynamic activity and brain excitability is challenging because it requires simultaneous measurement of brain hemodynamic activity while applying non-invasive brain stimulation. There is also considerable inter-/intra-subject variability which both brain excitability and task-related hemodynamic responses are associated with. Here we proposed hierarchical Bayesian modeling to taking into account variability in the data at the individual and group levels, aiming to provide accurate and reliable statistical inferences on this research question. Methods: We performed a study on 16 healthy subjects with simultaneous Paired Associative Stimulation (Inhibitory PAS10, Excitatory PAS25, Sham) and functional Near-Infrared Spectroscopy (fNIRS) targeting the primary motor cortex (M1). PAS was applied to modulate the cortical function and induce plasticity. Before and after each intervention cortical excitability was measured by motor evoked potentials (MEPs), and the motor task-related hemodynamic response was measured using fNIRS. We constructed three models to encode 1) PAS effects on the M1 excitability; 2) PAS effects on the whole-time course of fNIRS hemodynamic responses to finger tapping tasks, and 3) the correlation between PAS effects on M1 excitability and PAS effects on task-related hemodynamic responses. Results: Significant increase of the cortical excitability was found after PAS25, whereas a small reduction of the cortical excitability was shown after PAS10 and no changes after sham. We found PAS effects on finger tapping evoked HbO/HbR within M1, around the peak of the hemodynamic time courses. Both HbO and HbR absolute amplitudes increased after PAS25 and decreased after PAS10. Cortical excitability changes and task-related HbO/HbR changes showed a high probability of being positively correlated, 0.77 and 0.79, respectively. The corresponding Pearson correlations were 0.58 (p<.0001, HbO with MEP) and 0.56 (p<.001, HbR with MEP), respectively. Conclusion: Benefiting from this original Bayesian data analysis, our results showed that PAS modulates task-related cortical hemodynamic responses in addition to M1 excitability. The fact that PAS effects on hemodynamic response were exhibited mainly around the peak of the hemodynamic time course may indicate that the intervention only increases metabolic demanding rather than modulating hemodynamic response function per se. Moreover, the positive correlation between PAS modulations of excitability and hemodynamic brings insights to understand the fundamental properties of cortical function and cortical excitability.