Effects of neuromodulation in a cortical network model of object working memory dominated by recurrent inhibition
Effects of neuromodulation in a cortical network model of object working memory dominated by recurrent inhibition
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DOI：
10.1023/a:1011204814320
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发表时间：
2001-07-01
影响因子：
1.2
通讯作者：
Wang, XJ
中科院分区：
文献类型：
--
作者：
Brunel, N;Wang, XJ
实验证据表明，工作记忆中项目的维持是通过大脑皮层选择性神经组件的持续活动实现的。来理解。对于这种现象背后的机制，有必要研究外部输入或神经调节是如何影响持续活动的。我们使用客体工作记忆的递归网络模型来解决这些问题。复发以抑制为主，尽管持续活动是通过兴奋性神经元的小亚群反复兴奋而产生的。我们的主要发现如下。(1)由于强烈的反馈抑制，持续性活动随网络外部驱动力的增加而呈倒U型变化。(2)瞬时外加激励可以使网络从选择的持续状态切换到自发状态。(3)在延迟期间，只要刺激强度不大，样本刺激在工作记忆中的维持不受干扰刺激(干扰物)的影响。另一方面，如果刺激强度足够大，干扰物会扰乱与样本相关的持续活动，网络只能保持对最后显示的刺激的记忆。(4)GABAA和NMDA电导的协同调节导致自发活动减少，持续活动增加；信噪比的增加增加了网络对干扰物的抵抗。(5)发现了两种产生持续活动对调制的倒U型依赖关系的机制。因此，本研究指出了在工作记忆状态下提高信噪比的几种机制。这些机制可以通过来自中脑的多巴胺能投射在前额叶皮质实现。
Experimental evidence suggests that the maintenance of an item in working memory is achieved through persistent activity in selective neural assemblies of the cortex. To understand the. mechanisms underlying this phenomenon, it is essential to investigate how persistent activity is affected by external inputs or neuromodulation. We have addressed these questions using a recurrent network model of object working memory. Recurrence is dominated by inhibition, although persistent activity is generated through recurrent excitation in small subsets of excitatory neurons.Our main findings are as follows. (1) Because of the strong feedback inhibition, persistent activity shows an inverted U shape as a function of increased external drive to the network. (2) A transient external excitation can switch off a network from a selective persistent state to its spontaneous state. (3) The maintenance of the sample stimulus in working memory is not affected by intervening stimuli (distractors) during the delay period, provided the stimulation intensity is not large. On the other hand, if stimulation intensity is large enough, distractors disrupt sample-related persistent activity, and the network is able to maintain a memory only of the last shown stimulus. (4) A concerted modulation of GABAA and NMDA conductances leads to a decrease of spontaneous activity but an increase of persistent activity; the enhanced signal-to-noise ratio is shown to increase the resistance of the network to distractors. (5) Two mechanisms are identified that produce an inverted U shaped dependence of persistent activity on modulation. The present study therefore points to several mechanisms that enhance the signal-to-noise ratio in working memory states. These mechanisms could be implemented in the prefrontal cortex by dopaminergic projections from the midbrain.