Department of Computational Biology, Royal Institute of Technology Stockholm, Sweden.
Front Comput Neurosci. 2011 May 3;5:13. doi: 10.3389/fncom.2011.00013. eCollection 2011.
This study proposes a computational model for attentional blink or "blink of the mind," a phenomenon where a human subject misses perception of a later expected visual pattern as two expected visual patterns are presented less than 500 ms apart. A neocortical patch modeled as an attractor network is stimulated with a sequence of 14 patterns 100 ms apart, two of which are expected targets. Patterns that become active attractors are considered recognized. A neocortical patch is represented as a square matrix of hypercolumns, each containing a set of minicolumns with synaptic connections within and across both minicolumns and hypercolumns. Each minicolumn consists of locally connected layer 2/3 pyramidal cells with interacting basket cells and layer 4 pyramidal cells for input stimulation. All neurons are implemented using the Hodgkin-Huxley multi-compartmental cell formalism and include calcium dynamics, and they interact via saturating and depressing AMPA/NMDA and GABA(A) synapses. Stored patterns are encoded with global connectivity of minicolumns across hypercolumns and active patterns compete as the result of lateral inhibition in the network. Stored patterns were stimulated over time intervals to create attractor interference measurable with synthetic spike traces. This setup corresponds with item presentations in human visual attentional blink studies. Stored target patterns were depolarized while distractor patterns where hyperpolarized to represent expectation of items in working memory. Simulations replicated the basic attentional blink phenomena and showed a reduced blink when targets were more salient. Studies on the inhibitory effect of benzodiazepines on attentional blink in human subjects were compared with neocortical simulations where the GABA(A) receptor conductance and decay time were increased. Simulations showed increases in the attentional blink duration, agreeing with observations in human studies. In addition, sensitivity analysis was performed on key parameters of the model, including Ca(2+)-gated K(+) channel conductance, synaptic depression, GABA(A) channel conductance and the NMDA/AMPA ratio of charge entry.
这项研究提出了一个注意瞬脱或“思维眨眼”的计算模型，这是一种现象，即当两个预期的视觉模式在不到 500 毫秒的时间间隔内呈现时，人类受试者会错过对后来预期的视觉模式的感知。一个被建模为吸引子网络的新皮层斑块以 100 毫秒的间隔被刺激 14 个模式序列，其中两个是预期的目标。被激活为吸引子的模式被认为是被识别的。一个新皮层斑块被表示为一个超柱的正方形矩阵，每个超柱包含一组具有内部和跨超柱的迷你柱的突触连接的迷你柱。每个迷你柱由具有相互作用的篮状细胞和用于输入刺激的层 4 金字塔细胞的局部连接的层 2/3 金字塔细胞组成。所有神经元都使用 Hodgkin-Huxley 多室细胞形式主义来实现，包括钙动力学，并且它们通过饱和和压抑 AMPA/NMDA 和 GABA(A) 突触相互作用。存储的模式是通过超柱之间的迷你柱的全局连接进行编码的，并且在网络中的侧抑制的作用下，活跃的模式相互竞争。随着时间的推移，存储的模式被刺激以创建可通过合成尖峰轨迹测量的吸引子干扰。这种设置对应于人类视觉注意瞬脱研究中的项目呈现。存储的目标模式被去极化，而干扰模式被超极化以表示工作记忆中的项目的预期。模拟复制了基本的注意瞬脱现象，并显示出当目标更突出时，瞬脱减少。与增加 GABA(A) 受体电导和衰减时间的新皮层模拟相比，比较了人类受试者中苯二氮䓬类药物对注意瞬脱的抑制作用的研究。模拟显示注意瞬脱持续时间增加，与人类研究中的观察结果一致。此外，对模型的关键参数进行了敏感性分析，包括 Ca(2+)-门控 K(+) 通道电导、突触抑制、GABA(A) 通道电导和 NMDA/AMPA 电荷进入的比率。
