2月3日《神經(jīng)科學(xué)雜志》（The Journal of Neuroscience）發(fā)表了神經(jīng)科學(xué)研究所神經(jīng)元信息處理和可塑性實(shí)驗(yàn)室關(guān)于聽皮層的調(diào)頻聲音方向選擇性形成的突觸機(jī)制的最新發(fā)現(xiàn)。博士研究生葉昌泉通過對(duì)大鼠初級(jí)聽皮層的在體膜片鉗電生理研究,，揭示初級(jí)聽皮層的調(diào)頻方向選擇性建立的多重突觸機(jī)制：包括聲音激活的興奮性突觸輸入的時(shí)間延遲在聲音頻率象限上有規(guī)律的變化,；興奮性和抑制性輸入的感受野在聲音頻段上的差異分布，即不同頻段聲音差異性地激活抑制性和興奮性輸入,。這項(xiàng)研究直接地驗(yàn)證了存在已久的感覺神經(jīng)元方向性特征建立的通用突觸機(jī)制模型,，也為了解大腦感覺處理信息的工作機(jī)制提供了實(shí)驗(yàn)基礎(chǔ),。
在自然環(huán)境中，許多聲音都具有調(diào)頻（frequency modulation）特性,，即聲音頻率在一定的頻譜范圍內(nèi)變化,。這種聲音頻率在不同方向（如低頻到高頻的升頻聲音，或高頻到低頻的降頻聲音）,、不同速率上變化的調(diào)頻特征在動(dòng)物和人類語音交流中普遍存在,，并攜帶了重要的語音信息，為動(dòng)物叫聲和人類語言的識(shí)別提供了至關(guān)重要的特征信息,。在大腦的聽覺信息傳遞通路中,，包括初級(jí)聽覺皮層在內(nèi)的一些功能核團(tuán)的神經(jīng)細(xì)胞表現(xiàn)出對(duì)聲音頻率變化（調(diào)頻）方向的強(qiáng)選擇性。這與視覺中樞中視覺神經(jīng)細(xì)胞對(duì)物體移動(dòng)方向的偏好性相類似,。人們一直在探索是什么神經(jīng)機(jī)制促使大腦感覺細(xì)胞表征這些外界信息中方向特征,，進(jìn)而來高效地編碼和處理外界感覺信息。此項(xiàng)工作是在神經(jīng)科學(xué)研究所章曉輝研究員課題組,、蒲慕明研究員實(shí)驗(yàn)室和加利福尼亞大學(xué)伯克利分校丹揚(yáng)教授的共同合作下完成,，并受到中科院“創(chuàng)新項(xiàng)目”和科技部“973”項(xiàng)目“腦結(jié)構(gòu)和功能的可塑性”的資助。（生物谷Bioon.com）
生物谷推薦原始出處：
The Journal of Neuroscience, February 3, 2010, 30(5):1861-1868; doi:10.1523/JNEUROSCI.3088-09.2010
Synaptic Mechanisms of Direction Selectivity in Primary Auditory Cortex
Chang-quan Ye,1 Mu-ming Poo,1,2 Yang Dan,2,3 and Xiao-hui Zhang1
1Institute of Neuroscience and State Key Laboratory of Neuroscience, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200031, China, 2Division of Neurobiology, Department of Molecular and Cell Biology and Helen Wills Neuroscience Institute, University of California, Berkeley, California 94720, and 3Howard Hughes Medical Institute, University of California, Berkeley, California 94720
Frequency modulation (FM) is a prominent feature in animal vocalization and human speech. Although many neurons in the auditory cortex are known to be selective for FM direction, the synaptic mechanisms underlying this selectivity are not well understood. Previous studies of both visual and auditory neurons have suggested two general mechanisms for direction selectivity: (1) differential delays of excitatory inputs across the spatial/spectral receptive field and (2) spatial/spectral offset between excitatory and inhibitory inputs. In this study, we have examined the contributions of both mechanisms to FM direction selectivity in rat primary auditory cortex. The excitatory and inhibitory synaptic inputs to each cortical neuron were measured by in vivo whole-cell recording. The spectrotemporal receptive field of each type of inputs was mapped with random tone pips and compared with direction selectivity of the neuron measured with FM stimuli. We found that both the differential delay of the excitatory input and the spectral offset between excitation and inhibition are positively correlated with direction selectivity of the neuron. Thus, both synaptic mechanisms are likely to contribute to FM direction selectivity in the auditory cortex. Finally, direction selectivity measured from the spiking output is significantly stronger than that based on the subthreshold membrane potentials, indicating that the selectivity is further sharpened by the spike generation mechanism.
