The generation of theta rhythm in hippocampal formation maintained in vitro

The most spectacular example of oscillations and synchrony which appear in the brain is the rhythmic slow activity (theta) of the limbic cortex. Theta rhythm is the best synchronized electroencephalographic activity that can be recorded from the mammalian brain. Hippocampal formation is considered to be the main structure involved in the generation of this activity. Although detailed studies of the physiology and pharmacology of theta‐band oscillations have been carried out since the early 1950s, the first demonstration of atropine‐sensitive theta rhythm, recorded in completely deafferented hippocampal slices of a rat, was performed in the second half of the 1980s. Since the discovery of cholinergically induced in vitro theta rhythm recorded from hippocampal formation slices, the central mechanisms underlying theta generation have been successfully studied in in vitro conditions. Most of these experiments were focused on the basic question regarding the similarities between the cholinergically induced theta activity and theta rhythm examined in vivo. The results of numerous in vitro experiments strongly suggest that cholinergically induced theta rhythm recorded in hippocampal slices is a useful analogue of theta observed in intact animals, and could be helpful in searching for the mechanisms of oscillations and synchrony in the central nervous system neuronal networks. The objective of the present review is to discuss the main results of experiments concerning theta oscillations recorded in in vitro conditions. It is our intent to provide, on the basis of these results, the characteristics of essential mechanisms underlying the generation of atropine‐sensitive in vitro theta.     

Phase coding by grid cells in unconstrained environments: two‐dimensional phase precession

Action potential timing is thought to play a critical role in neural representation. For example, theta phase precession is a robust phenomenon exhibited by spatial cells of the rat entorhinal–hippocampal circuit. In phase precession, the time a neuron fires relative to the phase of theta rhythm (6–10 Hz) oscillations in the local field potential reduces uncertainty about the position of the animal. This relationship between neural firing and behavior has made precession an important constraint for hypothetical mechanisms of temporal coding. However, challenges exist in identifying what regulates the spike timing of these cells. We have developed novel analytical techniques for mapping between behavior and neural firing that provide sufficient sensitivity to examine features of grid cell phase coding in open environments. Here, we show robust, omnidirectional phase precession by entorhinal grid cells in openfield enclosures. We present evidence that full phase precession persists regardless of how close the animal comes to the center of a firing field. Many conjunctive grid cells, previously thought to be phase locked, also exhibited phase coding. However, we were unable to detect directional‐ or field‐specific phase coding predicted by some variants of models. Finally, we present data that suggest bursting of layer II grid cells contributes to the bimodality of phase precession. We discuss implications of these observations for models of temporal coding and propose the utility of these techniques in other domains where behavior is aligned to neural spiking.     

高频振荡通气在成年人急性呼吸窘迫综合征的临床应用

背景 高频振荡通气(high-frequency oscillatory ventilation,HFOV)作为一种新的通气模式,具有高频率、小潮气量、高平均气道压的特点,近年来被成功应用于成年人急性呼吸窘迫综合征(acute respiratory distress syndrome,ARDS)的治疗.研究表明,HFOV在改善氧合、减少呼吸机相关性肺损伤(ventilator associated lung injury,VILI)方面较常规机械通气(conventional mechanical ventilation,CMV)具有优势.但其对ARDS病死率的影响尚不明确. 目的 通过归纳HFOV在成年人ARDS中的临床应用揭示HFOV的优势和缺陷. 内容 HFOV能够高效改善氧合、减少VILI,但不能减少ARDS的病死率.HFOV技术的最适患者的筛选、最佳使用时机、最佳参数的设定以及与其他治疗手段联用等问题有待进一步探索. 趋向 HFOV应用于ARDS的治疗需要更加深入的研究和探索.     

小儿腹腔结核高频超声表现

目的观察儿童腹腔结核高频超声表现。方法回顾性分析26例28天～16岁腹腔结核患儿高频超声声像图表现。结果高频超声声像图显示广泛性肠管壁增厚20例,广泛性壁层腹膜不均匀性增厚24例,15例腹腔、腹膜后淋巴结肿大,10例腹腔内见多个透声差的囊性包块,2例肝脾大、2例单肾体积增大,8例大量腹腔积液、4例中量、14例少量;胰腺均未见特殊改变。结论儿童腹腔结核以增殖和干酪病变为主,其高频超声表现有一定特异性,有助于早期诊断。     

无创呼吸机辅助治疗急性左心衰竭临床观察

目的对无创呼吸机辅助治疗急性左心衰竭临床效果进行分析。方法选取我院收治的急性左心衰竭患者162例,随机分为两组患者,单纯组患者80例,常规进行临床药物的静脉滴注和各项生命体征的监测;联合组患者82例,在常规治疗和监测基础上进行无创呼吸机辅助治疗,对比两组患者的临床治疗效果。结果联合组患者呼吸困难完全缓解时间、血氧饱和度监测值、低血氧发生比例、临床疗效显著优越于单纯组患者（P〈0．05）。两组患者均未发生因急救措施和用药导致严重不良后果发生。结论对于急性左心衰竭患者在常规治疗基础上,应用无创呼吸机进行辅助治疗,可明显提高临床治疗效果、缩短呼吸困难缓解时间、明显改善患者的血氧饱和度、减低低血氧的发生比例,提高成功救治几率,对于急性左心衰竭患者的治疗和康复具有重要的临床意义。     

无创呼吸机辅助通气治疗急性左心衰竭60例的临床分析

目的 探讨无创呼吸机辅助通气治疗急性左心衰竭的临床效果.方法 将本院收治急性左心衰竭患者60例随机分为治疗组和对照组,每组各30例.对照组采用常规药物治疗,治疗组在常规药物治疗的基础上给予无创呼吸机辅助通气治疗.观察并记录两组治疗前后平均动脉压（MAP）、呼吸频率（RR）、心率（HR）、动脉血气指标（PaO2）的变化.结果 治疗后,两组的MAP、RR、HR较治疗前明显降低,PaO2明显升高（P＜0.05）,治疗后,治疗组效果优于对照组（P＜0.05）;治疗组的总有效率为90.00％,高于对照组的70.00％（P＜0.05）.结论 无创呼吸机辅助通气治疗急性左心衰竭临床效果确切,可明显改善临床症状,缩短病程,值得临床应用和推广.     

高频喷射通气对老年无痛苦纤维支气管镜检 血气结果的影响*

目的观察高频喷射通气对老年无痛苦纤维支气管镜检患者血气结果的影响。方法 102例患者随机均分为两组,观察组喷射频率60次/min,对照组喷射频率25次/min。分别在麻醉前及喷射通气10 min时采股动脉血行血气分析,记录呛咳、呼吸抑制、体动反应和二氧化碳CO2蓄积例数。结果麻醉前及喷射通气10 min后动脉血氧分压(PaO2)、动脉血二氧化碳分压(PaCO2)和动脉血氧饱和度(SaO2)组间比较,差异均无统计学意义(P0.05)。每组喷射通气10 min后,PaO2、PaCO2和SaO2均明显升高,与麻醉前比较,差异有统计学意义(P 0.05)。观察组有4例、对照组有7例发生CO2蓄积,但PaCO265 mmHg,组间比较,差异无统计学意义(P0.05)。结论高频喷射通气可以为老年患者纤维支气管镜检查麻醉提供可靠的氧供,但不一定能阻止呼吸抑制等因素引起的CO2蓄积,应引起足够的临床重视。     

高频超声与CT诊断鼻骨骨折的应用价值比较

目的 比较高频超声与CT诊断鼻骨骨折的临床价值。方法 回顾性分析经手术确诊的186例鼻骨骨折患者的术前高频超声和CT检查资料,比较两种检查方法对鼻骨骨折的总体检出率及不同类型骨折检出阳性率。结果 高频超声和CT对鼻骨骨折的总体检出率分别为（91.4%、94.6%）,差异无统计学意义。高频超声对单纯线性骨折的检出阳性率（55.4%）高于CT（48.9%）,差异有统计学意义（P＜0.05）;对粉碎性骨折的检出阳性率高频超声（29.6%）与CT相近（27.9%）,差异无统计学意义;对复合性骨折检出阳性率高频超声（6.5%）低于CT（17.7%）,差异有统计学意义（P＜0.05）。结论 高频超声安全、价廉、便捷,可作为鼻骨骨折影像学检查的一项重要补充,值得临床推广应用。