稳态视觉诱发电位频率识别算法研究进展

稳态视觉诱发电位是脑-机接口系统中常用的控制信号之一。基于稳态视觉诱发电位的脑-机接口具有高信息传输率、训练时间短等优点,已成为脑-机接口研究领域的一个重要分支。本文从无监督学习算法、有监督学习算法和深度学习算法三个方面,归纳了近五年稳态视觉诱发电位频率识别算法研究的主要进展,并展望了值得关注的若干前沿问题和研究方向。     

The amplitude and phase precision of 40 Hz auditory steady-state response depend on the level of arousal

The aim of this study was to investigate, in healthy subjects, the modulation of amplitude and phase precision of the auditory steady-state response (ASSR) to 40 Hz stimulation in two resting conditions varying in the level of arousal. Previously, ASSR measures have shown to be affected by the level of arousal, but the findings are somewhat controversial. Generally, ASSR is diminished in sleep but it may be increased in drowsiness. Besides, ASSR reduction has been observed in schizophrenia. However, schizophrenic patients are known to have a disturbance of arousal level, what makes it pertinent to know the effects of fluctuations in arousal on passive response to gamma-range stimulation. In nine healthy volunteers trains of 40 Hz click stimuli were applied during two conditions: in the “high arousal” condition subjects were sitting upright silently reading a book of interest; in the “low arousal” condition subjects were sitting in a reclined position with eyes closed and the lights turned off. The 64-channel EEG data was wavelet transformed and the amplitude and phase precision of the wavelet transformed evoked potential were decomposed by the recently proposed multi-subject non-negative multi-way factorization (NMWF) (Morup et al. in J Neurosci Methods 161:361–368, 2007). The estimates of these measures were subjected to statistical analysis. The amplitude and phase precision of the ASSR were significantly larger during the low arousal state compared to the high arousal condition. The modulation of ASSR amplitude and phase precision by differences in the arousal level during recording warrants caution when investigating oscillatory brain activity and interpreting the findings of reduced ASSR in schizophrenia. It also emphasizes the necessity of standardized recording procedures and monitoring the level of arousal during ASSR testing.     

Dark rearing alters the short-term synaptic plasticity in visual cortex

The strength of all chemical synapses can be rapidly up- or down-regulated by their recent activities to reshape the postsynaptic signal through a mechanism of short-term facilitation or depression. It is also true that sensory experience is essential for maturation of cortical circuits and function. We studied the effect of sensory experience on the short-term plasticity in brain slices of rat visual cortex. Repetitive stimulation was applied in layer II/III and the response of pyramidal neuron in layer V was examined by whole-cell recording. We deprived the visual experience of rats by rearing the animals in dark environment. We found that dark rearing (DR) had no effects on paired-pulse interactions of either excitatory postsynaptic currents (EPSCs) or inhibitory postsynaptic currents (IPSCs). However, DR increased the level of IPSCs steady-state depression at stimulation frequency of 20Hz or more. This result, together with the finding that DR reduced the excitability of neural circuit in visual cortex, suggested a compensatory mechanism, which may be important in enhancing the network excitability at a time when synapses are immature.     

Continuous infusion of cefepime and neurotoxicity: a retrospective cohort study

ObjectivesNeurotoxicity related to cefepime is increasingly reported in the literature but specific data concerning continuous infusion (CI) of the drug are still lacking. Our primary objective was to evaluate the incidence of neurotoxicity related to CI of cefepime and the associated risk factors. Our secondary objectives were to analyse the plasma cefepime concentrations and to define the threshold above which neurotoxicity occurs.MethodsIn this single-centre retrospective cohort study, all adult patients who underwent at least one cefepime therapeutic drug monitoring (TDM) and were treated with CI of 4 g/day between January 2017 and June 2019 were included. Neurotoxicity was evaluated according to a strict definition and was correlated with steady-state concentration at the time of toxicity presentation.ResultsNinety-eight patients with 201 cefepime TDM studies were included, with an incidence of neurotoxicity of 14.3% (14/98). Patients with neurotoxicity had more often underlying brain disease (35.7% (5/14) vs 11.9% (10/84), p = 0.030)) and higher steady-state concentrations (mean ± standard deviation 71.8 ± 32.9 mg/L vs 49.6 ± 30.6, p = 0.036) than the others. A receiver operating characteristic curve analysis yielded a cefepime steady-state concentration of 63.2 mg/L as the best cut-off point between patients with or without neurotoxicity. A mean steady-state concentration of 46.4 mg/L was achieved if the dosages of cefepime were adapted to renal function which was under our threshold concentration but above our highest pharmacokinetic/pharmacodynamic target of 32–40 mg/L.ConclusionsOur results suggest that 4 g/day of cefepime adapted to renal function and infused over 24 h is a trade-off for the risk/benefit ratio, when used empirically.     

径向基神经网络预测氯氮平血药浓度

目的:评价用径向基(RBF)神经网络所建立的预测氯氮平稳态血药浓度模型的预测性能。方法:将数据分为训练集、校验集和测试集来建立获取输入、输出变量两者间关系的RBF网络模型,其中以患者的性别、年龄、体重、剂量、血压、多项生理生化指标等37项参数为输入变量,氯氮平稳态血药浓度为输出变量。用训练集和校验集的网络计算输出值与目标输出值之间的均方差(MSE)和相关系数(R)来综合评价网络模型的学习效果,用测试集的网络计算输出值与目标输出值之间的MSE和R来评价网络模型的预测性能。结果:当扩展系数(SP)值为3.0时,训练集的MSE为1.33×10-5、R值为0.99985,校验集的MSE为0.002833、R值为0.97186,测试集的MSE为0.005439、R值为0.93676,网络模型的预测效果和泛化能力较好。结论:RBF网络用于预测氯氮平稳态血药浓度的研究是可行和有效的。     

Presence of strong harmonics during visual entrainment: a magnetoencephalography study

Visual neurons are known to synchronize their firing with stimuli that flicker at a constant rate (e.g. 12Hz). These so-called visual steady-state responses (VSSR) are a well-studied phenomenon, yet the underlying mechanisms are widely disagreed upon. Furthermore, there is limited evidence that visual neurons may simultaneously synchronize at harmonics of the stimulation frequency. We utilized magnetoencephalography (MEG) to examine synchronization at harmonics of the visual stimulation frequency (18Hz). MEG data were analyzed for event-related-synchronization (ERS) at the fundamental frequency, 36, 54, and 72Hz. We found strong ERS in all bands. Only 31% of participants showed maximum entrainment at the fundamental; others showed stronger entrainment at either 36 or 54Hz. The cortical foci of these responses indicated that the harmonics involved cortices that were partially distinct from the fundamental. These findings suggest that spatially-overlapping subpopulations of neurons are simultaneously entrained at different harmonics of the stimulus frequency.     

径向基神经网络预测利培酮的稳态血药浓度

目的:评价用径向基(RBF)神经网络所建立的预测利培酮稳态血药浓度模型的预测性能。方法:将数据分为训练集、校验集和测试集来建立获取输出变量与输入变量两者间关系的RBF网络模型,其中以患者的性别、年龄、体重、剂量、血压、多项生理生化指标等37项参数为输入变量,利培酮稳态血药浓度为输出变量。用训练集和校验集的网络计算输出值与目标输出值之间的均方差(MSE)和相关系数(R)来综合评价网络模型的学习效果,用测试集的网络计算输出值与目标输出值之间的MSE和R来评价网络模型的预测性能。结果:当扩展系数值为1.5时,训练集的MSE为6.93×10-6,R值为0.99988;校验集的MSE为8.24×10-3,R值为0.86669;测试集的MSE为8.58×10-3,R值为0.80899;网络模型的预测效果和泛化能力较好。结论:RBF网络用于预测利培酮稳态血药浓度的研究是可行的。     

左氧氟沙星对慢性阻塞性肺疾病急性加重患者的多索茶碱血药浓度的影响研究

目的:考察左氧氟沙星(LVFX)对多索茶碱(Dox)稳态谷血药浓度的影响,研究2种药物合用在慢性阻塞性肺疾病急性加重(AECOPD)患者临床应用中的安全性。方法:通过高效液相色谱(HPLC)法测定Dox单用及其与LVFX合用时的稳态谷血药浓度,对结果进行卡方检验。结果:通过HPLC法测定Dox单用及其与LVFX合用时的稳态血药浓度均在2～10μg·mL-1内,卡方检验统计量为1.250,概率P=0.741,按α=0.05水准,可认为2组数据无差别,即LVFX和Dox合用对Dox稳态谷血药浓度无影响。结论:临床上两药合用时,虽然LVFX对Dox的分布动力学有所影响,但不影响人体内Dox稳态谷血药浓度,合用时Dox不需要调整给药剂量。     

Pattern of cortical activation during processing of aversive stimuli in traumatized survivors of war and torture

Posttraumatic stress disorder (PTSD) has been associated with an altered processing of threat-related stimuli. In particular, an attentional bias towards threat cues has been consistently found in behavioral studies. However, it is unclear whether increased attention towards threat cues translates into preferential processing as neurophysiological studies have yielded inconsistent findings. The aim of the present study was to investigate the neocortical activity related to the processing of aversive stimuli in patients with PTSD. 36 survivors of war and torture with PTSD, 21 Trauma Controls and 20 Unexposed Subjects participated in a visual evoked magnetic field study using flickering pictures of varying affective valence as stimulus material. Minimum norm source localization was carried out to estimate the distribution of sources of the evoked neuromagnetic activity in the brain. Statistical permutation analyses revealed reduced steady-state visual evoked field amplitudes over occipital areas in response to aversive pictures for PTSD patients and for Trauma Controls in comparison to unexposed subjects. Furthermore, PTSD patients showed a hyperactivation of the superior parietal cortex selectively in response to aversive stimuli, which was related to dissociative symptoms as well as to torture severity. The results indicate a different pattern of cortical activation driven by aversive stimuli depending on the experience of multiple traumatic events and PTSD. Whereas, a decreased visual processing of aversive stimuli seems to be associated with trauma exposure in general, the superior parietal activity might represent a specific process linked to the diagnosis of PTSD.