González-Burgos Guillermo, Krimer Leonid S, Urban Nathaniel N, Barrionuevo Germán, Lewis David A
Department of Neuroscience, University of Pittsburgh, Pittsburgh, PA 15213-2593, USA.
Cereb Cortex. 2004 May;14(5):530-42. doi: 10.1093/cercor/bhh015. Epub 2004 Mar 28.
Neurons in the monkey dorsolateral prefrontal cortex (DLPFC) fire persistently during the delay period of working memory tasks. To determine how repetitive firing affects the efficacy of synaptic inputs to DLPFC layer 3 neurons, we examined the effects of repetitive presynaptic stimulation on the amplitude and temporal summation of EPSPs. Recordings were obtained in monkey DLPFC brain slices from regular spiking (RS) pyramidal cells and two types of interneurons, fast spiking (FS) and adapting non-pyramidal (ANP) cells. Repetitive stimulation of presynaptic axons in layer 3 caused EPSP depression in RS and FS neurons, but EPSP facilitation in ANP cells. A shorter EPSP duration produced weaker temporal summation in FS neurons compared to the other cell classes. Thus, due to the combined effects of dynamic changes in EPSP amplitude and differences in temporal summation, the effect of a presynaptic spike train differed according to the postsynaptic cell class. Similar results were obtained when recording unitary EPSPs evoked in connected pairs of presynaptic RS pyramidal cells and postsynaptic RS, FS or ANP neurons. In addition, similar differences in the efficacy of sustained inputs among cell classes were observed when delay-related firing was reproduced in vitro by stimulating inputs with the timing of spike trains recorded from the DLPFC of monkeys performing a delayed-response task. We suggest that the transition from baseline firing rates to higher frequency delay-related firing may lead to the differential activation of distinct cell populations, with corresponding significant effects on the patterns of activity in local prefrontal circuits.
猴子背外侧前额叶皮层（DLPFC）中的神经元在工作记忆任务的延迟期持续放电。为了确定重复放电如何影响DLPFC第3层神经元突触输入的效能，我们研究了重复的突触前刺激对兴奋性突触后电位（EPSP）幅度和时间总和的影响。在猴子DLPFC脑片中记录了常规放电（RS）锥体神经元以及两种中间神经元，即快放电（FS）和适应性非锥体（ANP）细胞的活动。对第3层突触前轴突的重复刺激导致RS和FS神经元的EPSP抑制，但在ANP细胞中则导致EPSP易化。与其他细胞类型相比，较短的EPSP持续时间在FS神经元中产生较弱的时间总和。因此，由于EPSP幅度的动态变化和时间总和差异的综合作用，突触前脉冲序列的效应因突触后细胞类型而异。在记录连接的突触前RS锥体神经元与突触后RS、FS或ANP神经元对诱发的单突触EPSP时，也获得了类似的结果。此外，当通过以执行延迟反应任务的猴子DLPFC记录的脉冲序列的时间刺激输入，在体外再现延迟相关放电时，在不同细胞类型之间观察到了持续输入效能的类似差异。我们认为，从基线放电率到更高频率的延迟相关放电的转变可能导致不同细胞群体的差异性激活，对局部前额叶回路的活动模式产生相应的显著影响。
