Circuit dynamics and coding strategies in rodent somatosensory cortex
Circuit dynamics and coding strategies in rodent somatosensory cortex
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DOI：
10.1152/jn.2000.83.3.1158
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发表时间：
2000-03-01
影响因子：
2.5
通讯作者：
Simons, DJ
中科院分区：
文献类型：
--
作者：
Pinto, DJ;Brumberg, JC;Simons, DJ
先前的实验研究表明，在啮齿动物体感皮层的皮质桶和丘脑桶样神经元的反应，在处理丘脑信号的桶电路的积极作用。先前对同一系统的建模研究表明，桶电路的主要功能是使桶神经元的响应幅度对丘脑输入的时间分布特别敏感。具体而言，最初同步的丘脑输入强烈参与桶中的经常性兴奋性连接，并产生一种反应，这种反应短暂地承受了抑制回路的强阻尼效应。为了测试这一实验，我们记录了40个皮质桶神经元和63个丘脑桶状神经元引起的晶须偏转速度和幅度不同的反应。这种刺激引起丘脑的反应曲线，其幅度和时间都不同。丘脑群体反应的幅度，测量为每个刺激诱发尖峰的平均数，增加偏转速度和幅度。另一方面，从人口刺激周时间直方图测量的初始同步的程度，是高度相关的晶须偏转的速度，偏转幅度对丘脑同步性的影响很小或没有。与模型的预测一致，皮质群体反应主要由触须速度决定，并且与丘脑神经元之间的初始同步程度高度相关（R-2 = 0.91），与诱发丘脑尖峰的平均数量（R-2 = 0.38）相比。单独来看，几乎所有皮质细胞的反应都与偏转速度呈正相关;这种同质性与模型提出的皮质反应对局部电路相互作用的依赖性是一致的。相比之下，单个丘脑神经元的反应差异很大。这些发现验证了建模研究的预测，更重要的是，证明了皮层处理传入信号的机制与丘脑反应中嵌入的神经代码的显着性密不可分，并且实际上决定了丘脑反应中嵌入的神经代码的显着性。
Previous experimental studies of both cortical barrel and thalamic barreloid neuron responses in rodent somatosensory cortex have indicated an active role for barrel circuitry in processing thalamic signals. Previous modeling studies of the same system have suggested that a major function of the barrel circuit is to render the response magnitude of barrel neurons particularly sensitive to the temporal distribution of thalamic input. Specifically, thalamic inputs that are initially synchronous strongly engage recurrent excitatory connections in the barrel and generate a response that briefly withstands the strong damping effects of inhibitory circuitry. To test this experimentally, we recorded responses from 40 cortical barrel neurons and 63 thalamic barreloid neurons evoked by whisker deflections varying in velocity and amplitude. This stimulus evoked thalamic response profiles that varied in terms of both their magnitude and timing. The magnitude of the thalamic population response, measured as the average number of evoked spikes per stimulus, increased with both deflection velocity and amplitude. On the other hand, the degree of initial synchrony, measured from population peristimulus time histograms, was highly correlated with the velocity of whisker deflection, deflection amplitude having little or no effect on thalamic synchrony. Consistent with the predictions of the model, the cortical population response was determined largely by whisker velocity and was highly correlated with the degree of initial synchrony among thalamic neurons (R-2 = 0.91), as compared with the average number of evoked thalamic spikes (R-2 = 0.38). Individually, the response of nearly all cortical cells displayed a positive correlation with deflection velocity; this homogeneity is consistent with the dependence of the cortical response on local circuit interactions as proposed by the model. By contrast, the response of individual thalamic neurons varied widely. These findings validate the predictions of the modeling studies and, more importantly, demonstrate that the mechanism by which the cortex processes an afferent signal is inextricably linked with, and in fact determines, the saliency of neural codes embedded in the thalamic response.