Cognitive-motor dual-task interference: A systematic review of neural correlates

Cognitive-motor interference refers to dual-tasking (DT) interference (DTi) occurring when the simultaneous performance of a cognitive and a motor task leads to a percentage change in one or both tasks. Several theories exist to explain DTi in humans: the capacity-sharing, the bottleneck and the cross-talk theories. Numerous studies investigating whether a specific brain locus is associated with cognitive-motor DTi have been conducted, but not systematically reviewed. We aimed to review the evidences on brain activity associated with the cognitive-motor DT, in order to better understand the neurological basis of the CMi. Results were reported according to the technique used to assess brain activity. Twenty-three articles met the inclusion criteria. Out of them, nine studies used functional magnetic resonance imaging to show an additive, under-additive, over- additive, or a mixed activation pattern of the brain. Seven studies used near-infrared spectroscopy, and seven neurophysiological instruments. Yet a specific DT locus in the brain cannot be concluded from the overall current literature. Future studies are warranted to overcome the shortcomings identified.     

参麦活血饮对糖尿病大鼠坐骨神经和红细胞山梨醇水平及神经功能的影响

目的 探讨糖尿病（DM）大鼠坐骨神经和红细胞山梨醇含量与神经功能之间的关系。观察参麦活血饮进行短期干预的作用和可能机制。方法 采用链脲佐菌素诱发DM大鼠模型。造模1周后用中成药参麦活血饮（成分为红参，麦冬，红花）治疗。用药4周后测定神经电生理，坐骨神经和红细胞山梨醇水平。结果 DM大鼠神经传导速度减慢，坐骨神经和红细胞山梨醇水平升高；经参麦活血饮治疗后上述改变减轻。同时，红细胞和坐骨神经山梨醇水平呈正相关；感觉神经传导速度与坐骨神经和红细胞山梨醇水平呈负相关，H反射与坐骨神经和红细胞山梨醇水平呈正相关。运动神经传导速度与坐骨神经和红细胞山梨醇水平无明显相关。结论 DM时红细胞山梨醇水平可反映坐骨神经山梨醇水平，亦能反映周围神经的病变程度，中药参麦活血饮可明显缓解DM大鼠周围神经的早期病变。     

Are neurophysiologic tests reliable,ultra-early prognostic indices after cardiac arrest?

ObjectivesDetermining early and reliable prognosis in comatose subjects after cardiac arrest is a central component of post–cardiac arrest care both for developing realistic prognostic expectations for families, and for better determining which resources are mobilized or withheld for individual patients. The aim of the study was to evaluate the prognostic accuracy of EEG and SEP patterns during the very early period (within the first 6 h) after cardiac arrest.MethodsWe retrospectively analysed comatose patients after CA, either inside or outside the hospital, in which prognostic evaluation was made during the first 6 h from CA. Prognostic evaluation comprised clinical evaluation (GCS and pupillary light reflex) and neurophysiological (electroencephalography (EEG) and somatosensory evoked potentials (SEP)) studies. Prognosis was evaluated with regards to likelihood of recovery of consciousness and also likelihood of failure to regain consciousness.ResultsForty-one comatose patients after cardiac arrest were included. All patients with continuous and nearly continuous EEG recovered consciousness. Isoelectric EEG was always associated with poor outcome. Burst-suppression, suppression and discontinuous patterns were usually associated with poor outcome although some consciousness recovery was observed. Bilaterally absent SEP responses were always associated with poor outcome. Continuous and nearly continuous EEG patterns were never associated with bilaterally absent SEP.ConclusionsDuring the very early period following cardiac arrest (first 6 h), EEG and SEP maintain their high predictive value to predict respectively recovery and failure of recovery of consciousness. A very early EEG exam allows identification of patients with very high probability of a good outcome, allowing rapid use of the most appropriate therapeutic procedures.     

Electrophysiological profile of the patients with MuSK positive myasthenia gravis

Abstract

Objectives:

To determine the electrophysiological profile of our cohort of patients with muscle-specific tyrosine kinase (MuSK) positive myasthenia gravis (MG).

Methods:

Repetitive nerve stimulation test (RNS) and jitter analysis using concentric needle electrode were performed in 31 MuSK and in 28 acetylcholine receptor (AChR) positive MG patients.

Results:

Pathological RNS was verified in 16 (51·6%) MuSK and 26 (92·9%) AChR MG patients (P < 0·01). Pathological jitter analysis was registered in 28 (90·3%) MuSK and 26 (92·9%) AChR MG patients (P > 0·05). Increased jitter was present in extensor digitorum communis (EDC) in 23 (74·2%) MuSK and in 25 (89·3%) AChR MG patients (P > 0·05) as well as in orbicularis oculi (OO) muscle in 24 (85·7%) MuSK and 22 (81·5%) AChR MG patients (P > 0·05). Lower mean value of mean consecutive difference (MCD) and fewer potential pairs with increased jitter were registered in MuSK MG compared to AChR MG patients only in EDC muscle (P < 0·05). In MuSK MG patients, increased jitter was observed to be more frequent in patients with longer disease duration (P < 0·05) and also in those patients exhibiting more severe disease forms (P < 0·01) only in EDC muscle.

Discussion:

Repetitive nerve stimulation test has low sensitivity in MuSK MG patients, while jitter analysis shows high sensitivity, especially in facial muscles. The EDC muscle in MuSK MG patients usually shows increased jitter in more severe disease forms and later in the course of the disease.     

Implanted medical devices or other strong sources of interference are not barriers to magnetoencephalographic recordings in epilepsy patients

ObjectiveLocalization accuracy in magnetoencephalography (MEG) recordings is highly dependent on signal to noise ratio, which is difficult to control.MethodsWe have post-processed our data in order to reduce noise to a level permitting adequate source localization with equivalent current dipole methods. In 30 consecutive epilepsy patients, MEG was recorded using a whole-head MEG system consisting of 204 planar gradiometer and 102 magnetometers, with simultaneous EEG. Data were reviewed to identify interictal spikes. The initial analysis was done after employing a spatiotemporal signal space separation (tSSS) method. A total of 18 dipole clusters in 15 patients were reanalyzed without tSSS, to compare the number, goodness of fit, and locations of acceptable dipoles before and after processing.ResultsIn 8 of 18 clusters, although acceptable dipole clusters were captured before processing, there was a clear improvement of all parameters with tSSS. In another 5 clusters, all from patients with vagus nerve stimulators, there were few or no acceptable dipoles before processing, but sufficient dipole clusters were obtained with tSSS.ConclusionIn contrast to volunteer research subjects, clinical patients cannot be expected to cooperate as fully, and their MEG data are likely to include more interference. This study demonstrates that processing the MEG data with a method to eliminate artifact arising from outside the brain significantly improves the data.SignificanceIn some cases, this improvement can mean the difference between satisfactory dipole fits vs no possible localization.     

稀释性贫血对大脑影响的研究进展

背景 传统观念认为血液稀释不会对脑代谢和脑功能造成明显损害.但最近一些研究表明围术期使用血液稀释技术造成的急性贫血可能对大脑产生不利影响. 目的 探讨急性贫血导致的脑损伤及相关机制,为合理应用血液稀释技术提供理论依据. 内容 主要阐述急性贫血与术后认知功能障碍、创伤后继发性脑损伤及蛛网膜下腔出血预后之间的关系.另一方面,阐述一氧化氮合酶(nitric oxide synthase,NOS)、缺氧诱导因子(hypoxia inducible factor,HIF)-1α、HIF-反应分子及炎症因子等在急性贫血致脑损伤中的作用. 趋向 围术期血液稀释导致的急性贫血可能影响脑功能,采取优化措施将使这种技术在临床上得到更合理的应用.     

Progressive sensory nerve dysfunction in amyotrophic lateral sclerosis: a prospective clinical and neurophysiological study

Sensory nerve function was determined in 19 patients with amyotrophie lateral sclerosis (ALS), using a battery of clinical and neurophysiological tests. This assessment was repeated on 12 patients after intervals of 6–18 months. Twelve controls were also studied. In the ALS group, only 2 patients had noticed mild sensory symptoms and none had sensory signs. Between successive studies the vibration thresholds increased, but not to a significant degree. ALS patients showed a significant fall in amplitude of the sensory nerve action potentials in the median, radial, and sural nerves (P < 0.04); sensory nerve conduction velocity did not alter. The median nerve somatosensory evoked potential N19 latency showed a highly significant increase (P < 0.008). Significant subclinical deterioration in sensory nerve function occurs in ALS, and parallels the progressive motor decline. Neuronal degeneration in ALS is not restricted to motor neurons.     

Development of New Pharmacological Agents for Epilepsy: Lessons from the Kindling Model

Summary: The greatest value of the kindling model for new therapy of epilepsy almost certainly lies in elucidating the molecular basis of its development and persistence. Such an understanding may provide a foundation for therapies aimed at prevention or perhaps even cure of some forms of human epilepsy.     

Differences of In Vitro Electrophysiology of Hippocampal Neurons from Epileptic Patients with Mesiotemporal Sclerosis Versus Structural Lesions

In vitro electrophysiologic studies of animal hippocampal slice models of epilepsy have generated hypotheses regarding cellular pathophysiologies associated with epileptogenesis. We tested some of these hypotheses using in vitro intracellular recordings of hippocampal neurons from patients with intractable temporal lobe epilepsy. We compared the electrophysiology of hippocampal neurons from 14 patients with mesiotemporal sclerosis with hippocampal neurons from 7 epileptic patients with structural lesions near the hippocampal biopsy. Both spontaneous and stimulus-evoked synaptic function and action potential firing patterns were observed. Presumed pyramidal neurons from sclerotic hippocampus were significantly less likely to display stimulus-evoked inhibitory postsynaptic potentials (IPSPs) and were more likely to fire spontaneously in bursts of action potentials than were hippocampal neurons from patients with structural lesions. No significant differences were detected in spontaneous postsynaptic potentials, spontaneous rhythmic synaptic events, spontaneous or anode break action potentials, stimulus-evoked excitatory postsynaptic potentials, or stimulus-evoked action potential bursts. Cellular membrane parameters were similar in the two groups, including resting membrane potential, action potential amplitude, action potential half-width, action potential threshold, input resistance, time constant, input/output relationship, and afterhyperpolarization amplitude.     

Contribution of two movement detecting mechanisms to central and peripheral vision

Two mechanisms, one for the detection of fast, and the other for slow movement of a sinusoidal grating are identified, and investigated under central, parafoveal, and peripheral viewing conditions. The fast movement data is considered in terms of the Reichardt model, in which signals from two adjacent inputs are cross-correlated leading to halving of the spatial resolving power for movement detection, compared with that for pattern detection. The mechanism underlying slow movement detection is regarded as being closely related to pattern detection, probably at the single unit level. The characteristics of this mechanism are discussed in the light of recent electrophysiological experiments describing clusters of simple cells in the visual cortex with “directional preference” properties.