Kesner R P, Rolls E T
Department of Psychology, University of Utah, Salt Lake City 84112, USA.
Hippocampus. 2001;11(3):240-50. doi: 10.1002/hipo.1040.
One way that some types of short-term or working memory may be implemented in the brain is by using autoassociation networks that recirculate information to maintain the firing of a subset of neurons in what is termed an attractor state. We describe how long-term synaptic modification is necessary to set up the appropriate stable attractors, each one of which corresponds to a memory of a particular item. Once the synapses have been modified, any of the short-term memory states may be triggered by an appropriate input which starts the neurons firing in one of the attractors, and then the firing is maintained in that attractor by the already modified synapses, with no further synaptic modification necessary. This analysis leads to the prediction that if this type of implementation is used for working memory, then long-term synaptic modification may be necessary only during an acquisition phase of a task, and once the task has been acquired, the performance of the working memory task should be unimpaired if no further synaptic modification is allowed. We show that a considerable body of research findings on the effects of agents that block synaptic modification on working memory tasks can be understood in this way. Many of the findings are consistent with the hypothesis that blocking synaptic modification in the hippocampus impairs the acquisition, but not the later performance, of hippocampal-dependent working memory tasks.
大脑实现某些类型的短期或工作记忆的一种方式是通过使用自联想网络，该网络循环信息以维持所谓吸引子状态下一部分神经元的放电。我们描述了长期突触修饰对于建立适当的稳定吸引子是必要的，每个吸引子都对应于特定项目的记忆。一旦突触被修饰，任何短期记忆状态都可以由适当的输入触发，该输入使神经元在其中一个吸引子中开始放电，然后放电通过已经修饰的突触在该吸引子中维持，无需进一步的突触修饰。该分析得出预测，如果这种类型的实现方式用于工作记忆，那么长期突触修饰可能仅在任务的获取阶段是必要的，并且一旦任务被获取，如果不允许进一步的突触修饰，工作记忆任务的表现应该不受损害。我们表明，关于阻断突触修饰的药物对工作记忆任务影响的大量研究结果可以用这种方式来理解。许多研究结果与以下假设一致，即阻断海马体中的突触修饰会损害依赖海马体的工作记忆任务的获取，但不会损害其后期表现。
