Institute of Neuroinformatics, University & ETH Zürich, Winterthurerstrasse 190, 8057, Zürich, Switzerland,
Cogn Neurodyn. 2007 Sep;1(3):225-35. doi: 10.1007/s11571-007-9017-x. Epub 2007 Jul 14.
It was often reported and suggested that the synchronization of spikes can occur without changes in the firing rate. However, few theoretical studies have tested its mechanistic validity. In the present study, we investigate whether changes in synaptic weights can induce an independent modulation of synchrony while the firing rate remains constant. We study this question at the level of both single neurons and neuronal populations using network simulations of conductance based integrate-and-fire neurons. The network consists of a single layer that includes local excitatory and inhibitory recurrent connections, as well as long-range excitatory projections targeting both classes of neurons. Each neuron in the network receives external input consisting of uncorrelated Poisson spike trains. We find that increasing this external input leads to a linear increase of activity in the network, as well as an increase in the peak frequency of oscillation. In contrast, balanced changes of the synaptic weight of excitatory long-range projections for both classes of postsynaptic neurons modulate the degree of synchronization without altering the firing rate. These results demonstrate that, in a simple network, synchronization and firing rate can be modulated independently, and thus, may be used as independent coding dimensions.
有报道和研究表明，尽管神经元的发放频率不变，但其发放仍可能同步。然而，很少有理论研究对其机制有效性进行测试。在本研究中，我们通过基于电导的整合发放神经元的网络模拟，在单个神经元和神经元群体水平上研究了突触权重的变化是否可以在保持发放率不变的情况下，对同步性进行独立调节。该网络由一个单层组成，包括局部兴奋性和抑制性的递归连接，以及靶向两类神经元的长程兴奋性投射。网络中的每个神经元都接收由不相关泊松尖峰序列组成的外部输入。我们发现，增加这种外部输入会导致网络活动的线性增加，以及振荡的峰值频率增加。相反，兴奋性长程投射的突触权重的平衡变化调节了同步的程度，而不改变发放率。这些结果表明，在一个简单的网络中，同步和发放率可以独立调节，因此，它们可能被用作独立的编码维度。
