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The research described above on persistent firing of certain neurons in the delay period of working memory tasks shows that the brain has a mechanism of keeping representations active without external input. Keeping representations active, however, is not enough if the task demands maintaining more than one chunk of information. In addition, the components and features of each chunk must be bound together to prevent them from being mixed up. For example, if a red triangle and a green square must be remembered at the same time, one must make sure that "red" is bound to "triangle" and "green" is bound to "square". One way of establishing such bindings is by having the neurons that represent features of the same chunk fire in synchrony, and those that represent features belonging to different chunks fire out of sync. In the example, neurons representing redness would fire in synchrony with neurons representing the triangular shape, but out of sync with those representing the square shape. So far, there is no direct evidence that working memory uses this binding mechanism, and other mechanisms have been proposed as well. It has been speculated that synchronous firing of neurons involved in working memory oscillate with frequencies in the theta band (4 to 8 Hz). Indeed, the power of theta frequency in the EEG increases with working memory load, and oscillations in the theta band measured over different parts of the skull become more coordinated when the person tries to remember the binding between two components of information.

The research described above on persistent firing of certain neurons in the delay period of working memory tasks shows that the brain has a mechanism of keeping representations active without external input. Keeping representations active, however, is not enough if the task demands maintaining more than one chunk of information. In addition, the components and features of each chunk must be bound together to prevent them from being mixed up. For example, if a red triangle and a green square must be remembered at the same time, one must make sure that "red" is bound to "triangle" and "green" is bound to "square". One way of establishing such bindings is by having the neurons that represent features of the same chunk fire in synchrony, and those that represent features belonging to different chunks fire out of sync. In the example, neurons representing redness would fire in synchrony with neurons representing the triangular shape, but out of sync with those representing the square shape. So far, there is no direct evidence that working memory uses this binding mechanism, and other mechanisms have been proposed as well. It has been speculated that synchronous firing of neurons involved in working memory oscillate with frequencies in the theta band (4 to 8 Hz). Indeed, the power of theta frequency in the EEG increases with working memory load, and oscillations in the theta band measured over different parts of the skull become more coordinated when the person tries to remember the binding between two components of information.

上述关于工作记忆任务延迟期间某些神经元持续放电的研究表明，大脑有一种在没有外部输入的情况下保持表征活跃的机制。然而，如果任务需要维护多个信息块，仅仅保持表示活动是不够的。此外，必须将每个块的组件和特性绑定在一起，以防止它们混在一起。例如，如果必须同时记住一个红色三角形和一个绿色正方形，就必须确保“红色”与“三角形”绑定，而“绿色”与“正方形”绑定。建立这种结合的一种方法是让神经元以同步的方式表现同一块发出的特征，而那些表现不同块发出的特征的神经元则同步发出。在这个例子中，代表红色的神经元会与代表三角形的神经元同步激发，但与代表正方形的神经元不同步。到目前为止，还没有直接的证据表明工作记忆使用这种结合机制，其他机制也被提出。据推测，与工作记忆有关的神经元的同步放电在 θ 波段(4ー8赫兹)振荡。事实上，脑电图中 θ 频率的力量随着工作记忆负荷的增加而增加，当人们试图记住信息的两个组成部分之间的联系时，在头骨不同部位测量到的 θ 波段的振荡变得更加协调。

上述关于工作记忆任务延迟期间某些神经元持续放电的研究表明，大脑有一种机制能在没有外部输入的情况下保持表征活跃。但不足以应对需要维护多个信息块的任务。此外每个组块的组件和特性必须绑定在一起，以防止和其它混淆。例如，如果必须同时记住一个红色三角形和一个绿色正方形，就必须确保“红色”与“三角形”绑定，而“绿色”与“正方形”绑定。建立这种结合的一种方法是让表现同一组块特征的神经元以同步激活，而那些表现不同组块特征的神经元则不同步激活。在这个例子中，代表红色的神经元会与代表三角形的神经元同步激活，但与代表正方形的神经元不同步。目前还没有直接的证据表明工作记忆使用这种结合机制，学界也提出了一些其他机制。工作记忆相关神经元的同步激活据推测是在θ波段(4ー8赫兹)振荡。脑电图θ频率的能量确实随工作记忆负荷的增加而增加，当被试试图记住信息的两个组成部分之间的联系时，在头骨不同部位测量到 θ 波段的振荡变得更加协调。

 

 

=== 脑内定位 Localization in the brain ===

=== 脑内定位 Localization in the brain ===