运用小波变换实现听觉诱发电位的单次提取

论述了运用小波变换进行听觉诱发电位单次提取的原理,方法和实验分析。结果表明,对单次试验信号,经小波变换及相关分析后,可从带自发脑电干扰的信号中提取诱发电位信号。小波变换分析与传统的叠加平均方法相比,可减少试验次数,缩短检测周期。     

A single gene error of noradrenergic axon growth synchronizes central neurones

One strategy for deciphering inherited neurological disease is to examine the expression of individual genes controlling the assembly and physiology of specific cell groups within the developing mammalian central nervous system (CNS). This neurogenetic approach, using defined single-locus mutations arising on coisogeneic mouse strains, has recently been used to analyse a major class of neuronal membrane diseases involving abnormal excitability, the epilepsies, and to identify examples of hereditary variation in signalling properties at central synapses. An interesting mutation, the Tottering (tg) gene, causes a delayed onset, recessive neurological disorder in the mouse featuring a stereotyped triad of ataxia, intermittent myoclonus and cortical spike-wave discharges accompanied by behavioural absence seizures which resemble petit mal epilepsy. Axon branches of the locus coeruleus, a noradrenergic brain-stem nucleus, hyperinnervate specific target regions of the tg brain. The number of parent coerulean perikarya is unaffected, indicating a true proliferation of the terminal axonal arbor. With the exception of this unusually precise error of axonal growth, no other cytopathology has been identified in the tg brain. Here I present evidence that selective lesions of the central noradrenergic axons early in development limit the expression of the disease.     

Serotonin and cyclic AMP close single K+ channels in Aplysia sensory neurones

We have identified a serotonin-sensitive K+ channel with novel properties. The channel is active at the testing potential; its gating is moderately affected by membrane potential and is not dependent on the activity of intracellular calcium ions. Application of serotonin to the cell body or intracellular injection of cyclic AMP causes prolonged and complete closure of the channel, thereby reducing the effective number of active channels in the membrane. The closure of the channel can account for the increases in the duration of the action potential, Ca2+ influx, and transmitter release which underlie behavioural sensitization, a simple form of learning.     

Ultra-fine frequency tuning revealed in single neurons of human auditory cortex

Just-noticeable differences of physical parameters are often limited by the resolution of the peripheral sensory apparatus. Thus, two-point discrimination in vision is limited by the size of individual photoreceptors. Frequency selectivity is a basic property of neurons in the mammalian auditory pathway. However, just-noticeable differences of frequency are substantially smaller than the bandwidth of the peripheral sensors. Here we report that frequency tuning in single neurons recorded from human auditory cortex in response to random-chord stimuli is far narrower than that typically described in any other mammalian species (besides bats), and substantially exceeds that attributed to the human auditory periphery. Interestingly, simple spectral filter models failed to predict the neuronal responses to natural stimuli, including speech and music. Thus, natural sounds engage additional processing mechanisms beyond the exquisite frequency tuning probed by the random-chord stimuli.     

Neuronal populations and single cells representing learned auditory objects

The neural representations associated with learned auditory behaviours, such as recognizing individuals based on their vocalizations, are not well described. Higher vertebrates learn to recognize complex conspecific vocalizations that comprise sequences of easily identified, naturally occurring auditory objects, which should facilitate the analysis of higher auditory pathways. Here we describe the first example of neurons selective for learned conspecific vocalizations in adult animals--in starlings that have been trained operantly to recognize conspecific songs. The neuronal population is found in a non-primary forebrain auditory region, exhibits increased responses to the set of learned songs compared with novel songs, and shows differential responses to categories of learned songs based on recognition training contingencies. Within the population, many cells respond highly selectively to a subset of specific motifs (acoustic objects) present only in the learned songs. Such neuronal selectivity may contribute to song-recognition behaviour, which in starlings is sensitive to motif identity. In this system, both top-down and bottom-up processes may modify the tuning properties of neurons during recognition learning, giving rise to plastic representations of behaviourally meaningful auditory objects.     

A Cl- conductance activated by hyperpolarization in Aplysia neurones

Although many voltage-gated cation channels have been described and extensively studied in biological membranes, there are very few examples of voltage-gated anion channels. Chloride conductances activated by depolarization have been observed in skate electroplaque and in frog and chick skeletal muscle. A Cl- conductance activated by hyperpolarization has been suggested both for frog muscle treated with acid (pH 5) solutions, and for crayfish muscle where it could account for the fact that the pronounced inward-going rectification of the I-V curve disappears if the fibres have been soaked in a Cl(-)-free solution. More recently, voltage-dependent anion channels extracted from biological membranes have been incorporated into artificial membranes. I now report that in Aplysia neurones, and in particular those in which the internal Cl- concentration has been increased, a Cl- conductance can be observed which is slowly activated by hyperpolarization and shows a vary steep voltage dependence. This time- and voltage-dependent Cl- conductance probably exists also in many other cells. Its presence might explain why it is difficult when using KCl-filled microelectrodes to maintain prolonged hyperpolarizations. This Cl- conductance constitutes a new type of inward-going rectification distinct both from the classical "anomalous rectification' which involves selective K+ channels and from the current termed if in heart muscle that is presently attributed to a cationic conductance.     

Monitoring the secretion from single cells with temporal and spatial resolution

The secretion from cells plays a significant role in life activites and in the fields of neurobiology, cell biology, clinic, pathology, pharmacology etc. Thus to investigate the secretion at the single cell level with the developing methods is a frontier cross-discipline research activity. The contents, methods and new progress of this research have been reviewed by electrochemical monitoring combined with patch-clamp techniques, fluorescent detection and immunoassay, and the prospects on the frontier of the research area have been discussed.     

一种有效的单频GPS相位模糊度解算方法

针对快速定位中GPS单频相位模糊度较难归整的问题,采用理论分析和实验验证的方法,推导了实时动态下相位平滑伪距的递推公式,给出了一些提高观测方程线性化初始值精度的思路。在分析了短时间段双差方程结构特性的基础上,提出采用迭代选权拟合法提高相位模糊度实数解精度的新方法。算例表明,该方法提高了模糊度实数解的精度和可靠性,缩小了模糊度的搜索空间,促进了模糊度解算效率和成功率,从而能促进单频GPS接收机在高精度快速定位中的应用。     

VRS系统流动端单历元整周模糊度搜索

为了实现VRS系统虚拟参考站和流动端单历元模糊度快速搜索,采用宽巷相位和C码伪距观测值组成联合双差观测方程,用改进LAMBDA方法搜索宽巷载波双差模糊度,并提出双频相位观测值组合模型逐星固定L1和L2双差模糊度,研究结果表明:该方法具有很高成功率和效率,单历元定位精度优于3 cm,该研究实现流动端单历元实时高精度动态定位。