Transcutaneous vagus nerve stimulation does not affect verbal memory performance in healthy volunteers

Introduction: Invasive vagus nerve stimulation (VNS) improves word recognition memory in patients with epilepsy. Recent studies with transcutaneous VNS (tVNS) have also shown positive effects on various subdomains of cognitive functioning in healthy volunteers. In this randomized, controlled, crossover study, we investigated the effect of tVNS on a word recognition memory paradigm in healthy volunteers to further investigate the potential of tVNS in the treatment of cognitive disorders. Methods: We included 41 healthy participants aged between 18 and 30 years (young age group) and 24 healthy participants aged between 45 and 80 years (older age group). Each participant completed a word recognition memory paradigm during three different conditions: true tVNS, sham, and control. During true tVNS, stimulation was delivered at the cymba conchae. Sham stimulation was delivered by stimulating the earlobe. In the control condition, no stimulation was given. In each condition, participants were asked to remember highlighted words from three test paragraphs. Accuracy scores were calculated for immediate recall after each test paragraph and for delayed recognition at the end of the paradigm. We hypothesized that highlighted words from paragraphs in the true tVNS condition would be more accurately recalled and/or recognized compared to highlighted words from paragraphs in the sham or control condition. Results: In this randomized study, tVNS did not affect the accuracy scores for immediate recall or delayed recognition in both age groups. The younger group showed significantly higher accuracy scores than the older group. The accuracy scores improved over time, and the most recently learned words were better recognized. Participants rated true tVNS as significantly more painful; however, pain was not found to affect accuracy scores. Conclusion: In this study, tVNS did not affect verbal memory performance in healthy volunteers. Our results could not replicate the positive effects of invasive VNS on word recognition memory in epilepsy patients. Future research with the aim of improving cognitive function should focus on the rational identification of optimized and individualized stimulation settings primarily in patients with cognitive deficits

Anesthesie met α2-agonisten bij de lama: een literatuuroverzicht aangevuld met eigen onderzoek

Many articles on anesthesia in llamas have been published Xylazme, combined with ketamine is the most frequently used injectable anesthetic protocol and it warrants an effective and reliable anesthesia to perform short procedures The use of other (alpha(2)-agonists is far less documented in the literature A study was carried out to evaluate and compare the anesthetic and cardiorespiratory effects of intramuscular medetomidine-ketamine and dexmedetomidine-ketamine in llamas The induction of anesthesia, cardiorespiratory parameters and the recovery time were similar in both groups However, during recovery, significantly more ataxia was observed in the llamas that received medetomidine than in the llamas that received dexmedetomidin

Soft, comfortable polymer dry electrodes for high quality ECG and EEG recording

Conventional gel electrodes are widely used for biopotential measurements, despite important drawbacks such as skin irritation, long set-up time and uncomfortable removal. Recently introduced dry electrodes with rigid metal pins overcome most of these problems; however, their rigidity causes discomfort and pain. This paper presents dry electrodes offering high user comfort, since they are fabricated from EPDM rubber containing various additives for optimum conductivity, flexibility and ease of fabrication. The electrode impedance is measured on phantoms and human skin. After optimization of the polymer composition, the skin-electrode impedance is only similar to 10 times larger than that of gel electrodes. Therefore, these electrodes are directly capable of recording strong biopotential signals such as ECG while for low-amplitude signals such as EEG, the electrodes need to be coupled with an active circuit. EEG recordings using active polymer electrodes connected to a clinical EEG system show very promising results: alpha waves can be clearly observed when subjects close their eyes, and correlation and coherence analyses reveal high similarity between dry and gel electrode signals. Moreover, all subjects reported that our polymer electrodes did not cause discomfort. Hence, the polymer-based dry electrodes are promising alternatives to either rigid dry electrodes or conventional gel electrodes

Neurophysiological investigations of drug resistant epilepsy patients treated with vagus nerve stimulation to differentiate responders from non-responders

Background and purpose In patients treated with vagus nerve stimulation (VNS) for drug resistant epilepsy (DRE), up to a third of patients will eventually not respond to the therapy. As VNS therapy requires surgery for device implantation, prediction of response prior to surgery is desirable. It is hypothesized that neurophysiological investigations related to the mechanisms of action of VNS may help to differentiate VNS responders from non-responders prior to the initiation of therapy. Methods In a prospective series of DRE patients, polysomnography, heart rate variability (HRV) and cognitive event related potentials were recorded. Polysomnography and HRV were repeated after 1 year of treatment with VNS. Polysomnography, HRV and cognitive event related potentials were compared between VNS responders (>= 50% reduction in seizure frequency) and non-responders. Results Fifteen out of 30 patients became VNS responders after 1 year of VNS treatment. Prior to treatment with VNS, the amount of deep sleep (NREM 3), the HRV high frequency (HF) power and the P3b amplitude were significantly different in responders compared to non-responders (P = 0.007; P = 0.001; P = 0.03). Conclusion Three neurophysiological parameters, NREM 3, HRV HF and P3b amplitude, were found to be significantly different in DRE patients who became responders to VNS treatment prior to initiation of their treatment with VNS. These non-invasive recordings may be used as characteristics for response in future studies and help avoid unsuccessful implantations. Mechanistically these findings may be related to changes in brain regions involved in the so-called vagal afferent network

EEG source connectivity to localize the seizure onset zone in patients with drug resistant epilepsy

Visual inspection of the EEG to determine the seizure onset zone (SOZ) in the context of the presurgical evaluation in epilepsy is time-consuming and often challenging or impossible. We offer an approach that uses EEG source imaging (ESI) in combination with functional connectivity analysis (FC) to localize the SOZ from ictal EEG. Ictal low-density-scalp EEG from 111 seizures in 27 patients who were rendered-seizure free after surgery was analyzed. For every seizure, ESI (LORETA) was applied on an artifact-free epoch selected around the seizure onset. Additionally, FC was applied on the reconstructed sources. We estimated the SOZ in two ways: (i)the source with highest power after ESI and (ii)the source with the most outgoing connections after ESI and FC. For both approaches, the distance between the estimated SOZ and the resected zone (RZ) of the patient were calculated. Using ESI alone, the SOZ was estimated inside the RZ in 31% of the seizures and within 10mm from the border of the RZ in 42%. For 18.5% of the patients, all seizures were estimated within 10mm of the RZ. Using ESI and FC, 72% of the seizures were estimated inside the RZ, and 94% within 10mm. For 85% of the patients, all seizures were estimated within 10mm of the RZ. FC provided a significant added value to ESI alone (p<0.001). ESI combined with subsequent FC is able to localize the SOZ in a non-invasive way with high accuracy. Therefore it could be a valuable tool in the presurgical evaluation of epilepsy

Heart rate, electrodermal responses and frontal alpha asymmetry to accepted and non-accepted solutions and drinks

Consumers' physiological responses, such as heart rate, electrodermal responses and frontal alpha activity can enhance the understanding of the consumers' food experience. This study looked at physiological responses of the autonomic nervous system (heart rate, electrodermal responses) as a measure for level of arousal, and to responses of the central nervous system (frontal alpha asymmetry, FAA) as a measure for approach/withdrawal motivational tendency, to accepted (liked) and non-accepted (disliked) solutions and drinks. Participants (n = 32, age range: 18-34 years) were presented with a universally accepted (sucrose) and non-accepted (caffeine) solution, a personally selected accepted and non-accepted drink, and plain water. Heart rate, heart rate variability, electrodermal activity and electro-encephalography for FAA at F7 and F8 (10/20 system, 25 channels, 256 Hz) were registered during tasting. Statistical analysis consisted of linear mixed model analyses. We found a significantly higher heart rate during tasting of the personally selected non-accepted drink and a significantly lower latency of the electrodermal response during tasting of the universally non-accepted solution and personally selected non-accepted drink. No significant results were observed for FAA. This is one of the first studies that examined physiological responses including frontal alpha asymmetry during actual tasting. This study provides an exploratory method to obtain implicit measurement of acceptance and food product-elicited emotion through physiological responses and supports the importance of the inclusion of implicit measures, next to explicit measures, in sensory evaluation of food products

Recent advances in devices for vagus nerve stimulation

Introduction: Vagus nerve stimulation (VNS) has become a valuable treatment option for refractory epilepsy and depression. To improve clinical efficacy and minimize side effects, novel device technology for VNS is under development and investigation.Areas covered: For epilepsy, the AspireSR (R), and SenTiva VNS therapy systems are the two most recently developed VNS devices. These novel devices have implemented a closed-loop approach and contain a cardiac based seizure detection algorithm. The mechanism of action of VNS remains to be further elucidated, but as preclinical research reveals VNS induced effects on brain plasticity, the autonomic nervous system and the inflammatory response, the indications of VNS are expanding. VNS devices are currently being investigated for stroke rehabilitation, treatment of chronic heart failure and rheumatoid arthritis. Recently devices to noninvasively affect vagus nerve functioning have been developed, with the aim of achieving similar effects without the drawbacks of a surgical procedure and continuous stimulation. Expert commentary: Several animal and human trials have shown promising results with minimal adverse events. However, further research needs to be conducted to validate the use of these devices and decide on optimal stimulation parameters