Activation of specific neural circuits in different layers of the primate dorsolateral prefrontal cortex (DLPFC) is essential for working memory, a core cognitive function. Recurrent excitation between pyramidal neurons in middle and deep layers of the DLPFC contributes to the laminar-specific activity associated with different working memory subprocesses. Excitation between cortical pyramidal neurons is mediated by glutamatergic synapses on dendritic spines, but whether the relative abundance of spines receiving cortical inputs differs between middle and deep cortical layers in human DLPFC is unknown. Additionally, GABAergic inputs to spines sculpt pyramidal neuron activity. Whether dendritic spines that receive a glutamatergic input from a cortical pyramidal neuron are targeted by GABAergic interneurons in the human DLPFC is unknown. Using triple-label fluorescence confocal microscopy, we found that 1) the density of spines receiving an input from a cortical pyramidal neuron is greater in the middle than in the deep laminar zone, 2) dendritic spines dually innervated by a cortical pyramidal neuron and an interneuron are present in the human DLPFC, and 3) the density of spines dually innervated by a cortical pyramidal neuron and an interneuron is also greater in the middle than in the deep laminar zone. Ultrastructural analyses support the presence of spines that receive a cortical pyramidal neuron synapse and an interneuron synapse in human and monkey DLPFC. These data support the notion that the DLPFC middle laminar zone is particularly endowed with a microcircuit structure that supports the gating, integrating and fine-tuning of synaptic information in recurrent excitatory microcircuits.

灵长类动物背外侧前额叶皮层 (DLPFC) 不同层中特定神经回路的激活对于工作记忆这一核心认知功能至关重要。 DLPFC 中层和深层锥体神经元之间的反复兴奋有助于与不同工作记忆子过程相关的层状特异性活动。皮层锥体神经元之间的兴奋是由树突棘上的谷氨酸突触介导的，但人类 DLPFC 中皮层中层和深层皮层中接受皮层输入的树突棘的相对丰度是否不同尚不清楚。此外，脊柱的 GABA 能输入塑造锥体神经元的活动。从皮质锥体神经元接收谷氨酸输入的树突棘是否是人类 DLPFC 中 GABA 能中间神经元的目标尚不清楚。使用三标记荧光共聚焦显微镜，我们发现：1）从皮质锥体神经元接收输入的树突棘密度在中部比在深层层流区更大，2）由皮质锥体神经元和树突棘双重支配的树突棘。中间神经元存在于人类 DLPFC 中，并且 3）由皮质锥体神经元和中间神经元双重支配的棘的密度在中部也比在深层流区更大。超微结构分析支持人类和猴子 DLPFC 中存在接收皮质锥体神经元突触和中间神经元突触的棘。这些数据支持这样的观点，即 DLPFC 中层状区特别具有微电路结构，支持周期性兴奋性微电路中突触信息的门控、集成和微调。