Bacci Alberto, Huguenard John R
Department of Neurology and Neurological Sciences, Stanford University School of Medicine, Stanford, California 94305, USA.
Neuron. 2006 Jan 5;49(1):119-30. doi: 10.1016/j.neuron.2005.12.014.
In vivo studies suggest that precise firing of neurons is important for correct sensory representation. Principal neocortical neurons fire imprecisely when repeatedly activated by fixed sensory stimuli or current depolarizations. Here we show that in contrast to pyramidal neurons, firing in neocortical GABAergic fast-spiking (FS) interneurons is quite precise. FS interneurons are self-innervated by powerful GABAergic autaptic connections reliably activated after each spike, suggesting that autapses strongly regulate FS-cell spike timing. Indeed, blockade of autaptic transmission degraded temporal precision in multiple ways. Under these conditions, realistic dynamic-clamp hyperpolarizing autapses restored precision of spike timing, even in the presence of synaptic noise. Furthermore, firing precision was increased in pyramidal neurons by artificial GABAergic autaptic conductances, suggesting that tightly coupled synaptic feedback inhibition regulates spike timing in principal cells. Thus, well-timed inhibition, whether autaptic or synaptic, facilitates precise spike timing and promotes synchronized cortical network oscillations relevant to several behaviors.
体内研究表明，神经元的精确放电对于正确的感觉表征很重要。当被固定的感觉刺激或电流去极化反复激活时，主要的新皮质神经元放电不精确。在这里我们表明，与锥体神经元不同，新皮质GABA能快速放电（FS）中间神经元的放电相当精确。FS中间神经元通过强大的GABA能自突触连接自我支配，每次动作电位后可靠地激活，这表明自突触强烈调节FS细胞的动作电位时间。事实上，自突触传递的阻断以多种方式降低了时间精度。在这些条件下，逼真的动态钳制超极化自突触恢复了动作电位时间的精度，即使存在突触噪声。此外，通过人工GABA能自突触电导增加了锥体神经元的放电精度，这表明紧密耦合的突触反馈抑制调节主要细胞的动作电位时间。因此，适时的抑制，无论是自突触的还是突触的，都有助于精确的动作电位时间，并促进与多种行为相关的同步皮质网络振荡。
