Canadian Centre for Behavioural Neuroscience, Department of Neuroscience, The University of Lethbridge, Lethbridge, Alberta, Canada.
Prog Brain Res. 2011;193:163-77. doi: 10.1016/B978-0-444-53839-0.00011-9.
The formation of memory and extraction of knowledge from it is the basis of intelligence. It is believed that, during slow-wave sleep, the brain reorganizes its connectivity matrix so as to store new information optimally. As the probability of direct synaptic connection between arbitrarily chosen neurons in the cortex is extremely low (on the order of 10(- 6)), a combination of modular and hierarchical organization appears to be necessary to enable rapid association of arbitrary items. During waking, an "index" of the neural pattern in lower order cortical modules may be created and stored in the highest order association cortex, the hippocampus, and broadcast back to the relevant cortical modules, where it is stored with the local data. In this manner, the pattern can be spontaneously reactivated and reinstated in all modules to enable the establishment of crossmodular connections, and replay of such patterns of neural activity or "phase sequences" has been observed in hippocampus and neocortex. In prefrontal cortex, the playback of "phase sequences" is associated with periods of intense upstate/downstate transitions and can be accelerated five- to eightfold relative to the waking state. The playback speed declines over time as does the strength of the replay, which is consistent with a simple decay of an asymmetric component of the synaptic weight matrix induced during the experience itself. Since the hippocampal events associated with memory reactivation (sharp-wave ripple events) tend to be correlated with up transitions in the neocortex, hippocampus may coordinate reactivation in neocortex, at least under some conditions.
记忆的形成和从中提取知识是智力的基础。据信，在慢波睡眠期间，大脑会重新组织其连接矩阵，以便最佳地存储新信息。由于皮质中任意选择的神经元之间直接突触连接的概率极低（约为 10(- 6)），因此似乎需要模块化和分层组织的组合才能实现任意项目的快速关联。在清醒状态下，可能会在较低阶皮质模块中创建神经模式的“索引”，并将其存储在最高阶的联合皮质（海马体）中，并将其广播回相关的皮质模块，在那里与本地数据一起存储。通过这种方式，可以在所有模块中自发地重新激活和恢复模式，从而建立跨模块连接，并且已经在海马体和新皮质中观察到这种神经活动模式或“相位序列”的重放。在前额叶皮质中，“相位序列”的重放与高强度的上下状态转换有关，并且可以相对于清醒状态加速五到八倍。随着时间的推移，重放速度会下降，重放的强度也会下降，这与在经历本身期间诱导的突触权重矩阵的不对称分量的简单衰减一致。由于与记忆再激活相关的海马体事件（尖波涟漪事件）往往与新皮质中的上转换相关，因此海马体至少在某些条件下可以协调新皮质中的再激活。
