Modeling the link between functional Imaging and neuronal activity: Synaptic metabolic demand and spike rates
Modeling the link between functional Imaging and neuronal activity: Synaptic metabolic demand and spike rates
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DOI：
10.1006/nimg.2002.1234
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发表时间：
2002-10-01
期刊：
影响因子：
5.7
通讯作者：
Stetter, M
中科院分区：
文献类型：
--
作者：
Almeida, R;Stetter, M
功能磁共振成像（fMRI）和正电子发射断层扫描（PET）测量反映了血流动力学的变化，这被认为与神经元群的局部突触输入有关。局部神经元尖峰活动被认为构成神经元编码和通讯的基础，但并没有直接反映在 fMRI/PET 测量中。我们使用周期性耦合的兴奋性和抑制性神经元群体的平均场神经元模型来表征突触活动（反映在 PET 和 fMRI 测量中）与神经元尖峰率（大脑区域的平均值）之间的关系。我们分析了许多案例的这种关系。对于单个大脑区域并且在其抑制性神经元没有外部输入的情况下，平均尖峰率和突触活动之间的关系是线性的。然而，在以下情况下会发现线性的偏离：（i）局部突触强度变化，（ii）外部输入变化，在抑制群体存在外部输入的情况下，或（iii）两个区域的平均尖峰率振荡之间的同步变化。我们进一步表明，在抑制群体存在外部输入的情况下，成像信号的增加可以反映平均尖峰活性的下降。当兴奋性群体的输入未达到激活阈值或两个区域的振荡之间存在某些同步时，突触活动也可能与沉默的神经元群体相关。总之，在根据平均尖峰率解释神经影像学结果时应谨慎。 (C) 2002 年爱思唯尔科学（美国）。
Functional magnetic resonance imaging (fMRI) and positron emission tomography (PET) measurements reflect changes in the hemodynamics which are thought to be related to local synaptic input to neuron populations. The local neuronal spiking activity, which is believed to form the basis of neuronal coding and communication, is not directly reflected in fMRI/ PET measurements. We used a mean-field neuronal model of recurrently coupled excitatory and inhibitory neuronal populations to characterize the relationship between the synaptic activity (reflected in the PET and fMRI measurements) and the neuronal spike rates, averaged over brain areas. We analyzed this relation for a number of cases. For a single brain area and in the absence of external input to its inhibitory neurons, the relation between average spike rates and synaptic activity is linear. However, departures from linearity are found when: (i) the local synaptic strengths vary, (ii) the external inputs vary, in the presence of external input to the inhibitory population, or (iii) the synchronization between oscillations of the average spike rates of two areas changes. We further show that an increase in the imaging signal can reflect a decrease in average spiking activity, in the presence of external input to the inhibitory population. Synaptic activity can also be associated with silent neuronal populations, when input to the excitatory population does not reach the activation threshold or for certain synchronizations between oscillations of two areas. In conclusion, caution should be used when interpreting neuroimaging results in terms of mean spike rates. (C) 2002 Elsevier Science (USA).