调频声频率变化率对大鼠听皮层神经元声反应的影响

采用在体细胞外单细胞记录方法,研究调频声频率变化率及时程对调频声所诱发的听皮层神经元反应的影响.实验在34只乌拉坦麻醉的SD大鼠上进行,在皮层41区记录了113个对调频声有反应的细胞电活动.观察发现,调频声刺激的时程和频率变化率发生改变,可对诱发的听皮层神经元反应的反应型式和放电频数产生影响.这种影响表明,听皮层在复杂声上传信息的处理过程中可能存在复杂的编码机制.     

电刺激大鼠mPFC对听皮层神经元听反应的影响

实验在40只成年SD大鼠上进行,使用常规电生理学方法,观察了电刺激大鼠内侧额叶前皮质(medial prefrontal cortex, mPFC)对听皮层神经元听反应的影响.在122个神经元上观察了电刺激mPFC对听反应的影响.对其中93个神经元作了详细分析发现,有73个神经元的听反应受到易化（39个,41.9%）或抑制（34个,36.6%）.刺激mPFC对听反应的影响存在最佳刺激间隔,大多数神经元（51个,69%）在10~15 ms之间.结果提示,大鼠mPFC可对听皮层神经元的听反应调制,这种调制可能是通过多级神经元环路实现的.     

小鼠下丘神经元对不同调制范围的调频声的扫频方向选择性

在自由声场刺激条件下,固定调频(frequency-modulated,FM)声的幅度和时程,改变调制范围(modulation range,MR)和扫频方向,记录和测定了小鼠下丘神经元对FM声上、下扫频方向的选择性,探讨了MR对神经元扫频方向选择性的影响.实验共记录到102个神经元,其中45个(44.1%)神经元表现...     

家兔杏仁基底核影响V1区神经电活动的研究

在10只马拉坦麻醉和三碘季胺酚麻痹的新西兰兔上用粗金属电极记录刺激杏仁在视皮层V1区的诱发电位活动，并考察其分布情况。当刺激杏仁基底核时，在整个视皮层V1区都记录到潜伏期为1～2ms的诱发电位，振幅最大的电位分布在V1区前部。刺激杏仁基底核还使视皮层光诱发电位的主反应受到抑制，作用的潜伏期为10ms，时程为20ms。这些结果显示，杏仁基底核可能有向视皮层V1区直接的纤维联系，其功能之一可能是介导杏仁体对外膝体视觉信息上传和处理的调控。     

家鸽前脑声反应神经元的分布及其特性的研究

实验在61只家鸽上完成。动物用三碘季胺酚麻痹,记录了前脑36个神经元的电活动。实验结果表明,对短声刺激具有反应的前脑神经元分散地分布在旧纹状体、上纹状体以及新纹状体内,但是大多数听神经元集聚在相当于Karten和Hodos氏鸽脑立体定位图谱P_(1～3),L或R_(1～3)以及H_(2～6)的坐标范围之内。这些对声刺激有反应的听神经元的潜伏期为5～42msec。在正常情况下,神经元的潜伏期很少变化。前脑听神经元既可以接受对侧耳的信息,也可以接受同侧耳的信息。在旧纹状体内来自双耳信息的聚合可能引起相互抑制的结果。     

家鸽前脑声反应神经元的分布及其特性的研究

实验在61只家鸽上完成。动物用三碘季胺酚麻痹,记录了前脑36个神经元的电活动。实验结果表明,对短声刺激具有反应的前脑神经元分散地分布在旧纹状体、上纹状体以及新纹状体内,但是大多数听神经元集聚在相当于Karten和Hodos氏鸽脑立体定位图谱P_(1-3),L或R_(1-3)以及H_(2-6)的坐标范围之内。这些对声刺激有反应的听神经元的潜伏期为5～42msec。在正常情况下,神经元的潜伏期很少变化。前脑听神经元既可以接受对侧耳的信息,也可以接受同侧耳的信息。在旧纹状体内来自双耳信息的聚合可能引起相互抑制的结果。     

大鼠杏仁体基底核对视皮层17区神经元电活动的抑制

实验在５５只Ｕｒｅｔｈａｎｅ麻醉的雄性Ｓ磊鼠上进行。采用电生理的胞外记录法,观察了电刺激杏杜体对视皮层１７区单个神经元的光反应及自发放电活动的影响。当刺激杏仁体基底核时,１２３个对闪光起反应的神经元中,有５７个单位的光反应受到了抑制（占４６．３％）。这种帽性影响的潜伏期多为５－５０ｍｓ（３３个单位）,抑制的有效时程为５－２０ｍｓ。本文对这种抑制性影响的可能途径和生物学意义进行了讨论。     

经颅磁声电刺激下皮层钙信号及突触传递特性的仿真与实验分析

为了探究经颅磁声电刺激(transcranial magneto-acoustic-electrical stimulation, TMAES)不同磁场强度和超声功率强度对工作记忆信息编码相关的皮层神经元钙信号及突触传递特性的影响,首先通过搭建基于磁声电效应改进的皮层锥体神经元模型,引入钙依赖神经递质释放的计算方法以计算TMAES引起的兴奋性突触后电位(excitatory postsynaptic potential, EPSP),以EPSP作为评价指标来评估不同TMAES磁场强度和超声功率强度下突触传递的短时程可塑性.随后使用光纤光度检测技术实时记录TMAES下小鼠前额叶皮层神经集群的钙信号,以揭示TMAES下钙依赖神经信息传递机制.仿真结果表明：TMAES不同磁场强度和超声功率强度对突触后响应的大小具有双向调节作用,其中,突触传递产生的短时程增强和抑制是由于TMAES下胞内钙浓度的变化引起的囊泡释放和囊泡耗竭.实验结论表明：TMAES对前额叶皮层神经元集群钙信号幅度和频率均有明显的调节作用,TMAES可以通过调节神经钙浓度进而影响突触间的信息传递.     

家兔杏仁基底核V1区神经电活动的研究

在１０只乌拉坦麻醉和三碘季胺酚麻痹的新西兰兔上用粗金属电极记录刺激杏仁在视皮层Ｖ１区的诱发电位活动，并考察其分布情况。当刺激杏仁基底核时，在整个视皮层Ｖ１区都记录到潜伏期为１￣２ｍｓ的诱发电位，振幅最大的电位分布在Ｖ１区前部。刺激杏仁基底核还使视皮层光诱发电位的主反应受到抑制，作用的潜伏期为１０ｍｓ，时程为２０ｍｓ。这此结果显示，杏仁基底核可能有向视皮层Ｖ１区直接的纤维联系，其功能之一可能是介导杏     

GABA能回路在听皮层神经元频率调谐中的作用

为了解神经抑制在听中枢神经元频率调谐过程中的作用,本研究采用多管玻璃微电极胞外记录单单位反应的方法观察了去r-氨基丁酸能抑制后大棕蝠(Eptesicusfuscus)听皮层神经元频率调谐特性的变化,结果显示:(1)97.9%的神经元频率调谐曲线扩宽,Qn值下降(p<0.0001);(2)绝大部分神经元的最小阈值下降(p<0.0001);(3)兴奋性调谐曲线面积增加(p<0.0001).该结果提供了GABA能回路参与蝙蝠听皮层神经元频率调谐的直接证据.     

Binaurality and azimuth tuning of neurons in the auditory cortex of the big brown bat

By using a combined closed and free-field stimulation system, binaurality and azimuth tuning of the neurons in the auditory cortex of the big brown bat, Eptesicus fuscus, were studied. A variety of azimuth-tuning functions were demonstrated for the binaural neurons. The large majority of EE (contralateral and ipsilateral excitatory) neurons exhibited azimuth selectivity with the best azimuths (BA) at contralateral 30(- 40(, some at ipsilateral 20(-40( and preferred azimuth ranges (PAR, response amplitude ≥75% of maximum) between 8( and 40(. Sound source azimuths strongly modulate spike counts with a mean modulation depth of 83.8% for EE neurons. EI (contralateral excitatory and ipsilateral inhibitory) neurons have simple azimuth tuning with BA located at contralateral 20(-40( and a broad PAR ranged from 30( to 55(. The present results suggest that azimuth-tuning characteristics of binaural neurons in the auditory cortex of the bat are of significance for acoustic behaviour.     

Topography of acoustic response characteristics in the auditory cortex of the Kunming mouse

Topography of acoustic response characteristics in the auditory cortex (AC) of the Kunming (KM) mouse has been examined by using microelectrode recording techniques. Based on best-frequency (BF) maps, both the primary auditory field (AI) and the anterior auditory field (AAF) are tonotopically organized with a counter running frequency gradient. Within an isofrequency stripe, the width of the frequency-threshold curves of single neurons increases, and minimum threshold (MT) decreases towards more ventral locations. BFs in AI and AAF range from 4 to 38 kHz. Auditory neurons with BFs above 40 kHz are located at the rostrodorsal part of the AC. The findings suggest that the KM mouse is a good model suitable for auditory research.     

脑对双耳听觉信息整合的神经机制

综述近60 a来有关脑对双耳听觉信息整合的神经机制的研究进展.首先介绍了脑处理双耳信息的神经解剖学基础，双耳神经元的分类及其生理特性，以及双耳神经元在听觉系统的拓扑学分布研究；然后对脑处理双耳听觉信息研究的热点领域进行了重点探讨，综述了上橄榄复合体、下丘和听皮层双耳神经元对双耳时间差和双耳强度差的编码方式，以及脑通过对这些参数的编码来分析声源方位的神经生理学研究进展；最后对该领域未来研究方向作展望.     

Sustained firing in auditory cortex evoked by preferred stimuli

It has been well documented that neurons in the auditory cortex of anaesthetized animals generally display transient responses to acoustic stimulation, and typically respond to a brief stimulus with one or fewer action potentials. The number of action potentials evoked by each stimulus usually does not increase with increasing stimulus duration. Such observations have long puzzled researchers across disciplines and raised serious questions regarding the role of the auditory cortex in encoding ongoing acoustic signals. Contrary to these long-held views, here we show that single neurons in both primary (area A1) and lateral belt areas of the auditory cortex of awake marmoset monkeys (Callithrix jacchus) are capable of firing in a sustained manner over a prolonged period of time, especially when they are driven by their preferred stimuli. In contrast, responses become more transient or phasic when auditory cortex neurons respond to non-preferred stimuli. These findings suggest that when the auditory cortex is stimulated by a sound, a particular population of neurons fire maximally throughout the duration of the sound. Responses of other, less optimally driven neurons fade away quickly after stimulus onset. This results in a selective representation of the sound across both neuronal population and time.     

Induction of visual orientation modules in auditory cortex

Modules of neurons sharing a common property are a basic organizational feature of mammalian sensory cortex. Primary visual cortex (V1) is characterized by orientation modules--groups of cells that share a preferred stimulus orientation--which are organized into a highly ordered orientation map. Here we show that in ferrets in which retinal projections are routed into the auditory pathway, visually responsive neurons in 'rewired' primary auditory cortex are also organized into orientation modules. The orientation tuning of neurons within these modules is comparable to the tuning of cells in V1 but the orientation map is less orderly. Horizontal connections in rewired cortex are more patchy and periodic than connections in normal auditory cortex, but less so than connections in V1. These data show that afferent activity has a profound influence on diverse components of cortical circuitry, including thalamocortical and local intracortical connections, which are involved in the generation of orientation tuning, and long-range horizontal connections, which are important in creating an orientation map.     

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.     

A disinhibitory microcircuit for associative fear learning in the auditory cortex

Learning causes a change in how information is processed by neuronal circuits. Whereas synaptic plasticity, an important cellular mechanism, has been studied in great detail, we know much less about how learning is implemented at the level of neuronal circuits and, in particular, how interactions between distinct types of neurons within local networks contribute to the process of learning. Here we show that acquisition of associative fear memories depends on the recruitment of a disinhibitory microcircuit in the mouse auditory cortex. Fear-conditioning-associated disinhibition in auditory cortex is driven by foot-shock-mediated cholinergic activation of layer 1 interneurons, in turn generating inhibition of layer 2/3 parvalbumin-positive interneurons. Importantly, pharmacological or optogenetic block of pyramidal neuron disinhibition abolishes fear learning. Together, these data demonstrate that stimulus convergence in the auditory cortex is necessary for associative fear learning to complex tones, define the circuit elements mediating this convergence and suggest that layer-1-mediated disinhibition is an important mechanism underlying learning and information processing in neocortical circuits.     

Material differences of auditory source retrieval: Evidence from event-related potential studies

Two event-related potential experiments were conducted to investigate the temporal and the spatial distributions of the old/new effects for the item recognition task and the auditory source retrieval task using picture and Chinese character as stimuli respectively. Stimuli were presented on the center of the screen with their names read out either by female or by male voice simultaneously during the study phase and then two testa were performed separately. One test task was to differentiate the old items from the new ones, and the other task was to judge the items read out by a certain voice during the study phase as targets and other ones as non-targets. The results showed that the old/new effect of the auditory source retrieval task was more sustained over time than that of the item recognition task in both experiments, and the spatial distribution of the former effect was wider than that of the latter one. Both experiments recorded reliable old/new effect over the prefrontal cortex during the source retrieval task. However, there existed some differences of the old/new effect for the auditory source retrieval task between picture and Chinese character, and LORETA source analysis indicated that the differences might be rooted in the temporal lobe. These findings demonstrate that the relevancy of the old/new effects between the item recognition task and the auditory source retrieval task supports the dual-process model; the spatial and the temporal distributions of the old/new effect elicited by the auditory source retrieval task are regulated by both the feature of the experimental material and the perceptual attribute of the voice.