Mechanism for top-down control of working memory capacity
Mechanism for top-down control of working memory capacity
复制标题
DOI：
10.1073/pnas.0901894106
复制
发表时间：
2009-04-21
影响因子：
11.1
通讯作者：
Compte, Albert
中科院分区：
文献类型：
--
作者：
Edin, Fredrik;Klingberg, Torkel;Compte, Albert
工作记忆容量，即我们可以暂时存储在工作记忆中的最大项目数量，可以很好地预测我们的一般认知能力。背外侧前额叶皮层和后顶叶皮层的神经活动与视觉空间工作记忆任务期间的记忆保留有关。顶叶皮层被认为是储存记忆的。然而，背外侧前额叶皮层（一个自上而下的控制区域）在纯粹的信息保留过程中的作用存在争议，并且调节能力的机制尚不清楚。在这里，我们提出背外侧前额叶皮层在工作记忆中的主要作用是提高顶叶记忆能力。此外，我们在生物物理皮层微电路模型中通过计算制定了增强机制，并推导出一个简单、明确的数学公式，将记忆容量与前额叶和顶叶模型参数相关联。对于生理上真实的参数值，顶叶皮质的侧向抑制将记忆能力限制为最多 2-7 个项目。然而，在高负荷下，兴奋性前额叶输入可以抵消抑制，从而提高顶叶能力。功能磁共振成像研究证实了模型的预测。我们的结果表明，尽管记忆存储在顶叶皮层中，但个体间记忆容量的差异部分取决于前额叶自上而下控制的强度。该模型提供了一个用于理解工作记忆自上而下控制的机制框架，并指定了前额叶和顶叶皮层对工作记忆容量的两种不同贡献。
Working memory capacity, the maximum number of items that we can transiently store in working memory, is a good predictor of our general cognitive abilities. Neural activity in both dorsolateral prefrontal cortex and posterior parietal cortex has been associated with memory retention during visuospatial working memory tasks. The parietal cortex is thought to store the memories. However, the role of the dorsolateral prefrontal cortex, a top-down control area, during pure information retention is debated, and the mechanisms regulating capacity are unknown. Here, we propose that a major role of the dorsolateral prefrontal cortex in working memory is to boost parietal memory capacity. Furthermore, we formulate the boosting mechanism computationally in a biophysical cortical microcircuit model and derive a simple, explicit mathematical formula relating memory capacity to prefrontal and parietal model parameters. For physiologically realistic parameter values, lateral inhibition in the parietal cortex limits mnemonic capacity to a maximum of 2-7 items. However, at high loads inhibition can be counteracted by excitatory prefrontal input, thus boosting parietal capacity. Predictions from the model were confirmed in an fMRI study. Our results show that although memories are stored in the parietal cortex, interindividual differences in memory capacity are partly determined by the strength of prefrontal top-down control. The model provides a mechanistic framework for understanding top-down control of working memory and specifies two different contributions of prefrontal and parietal cortex to working memory capacity.