Institute of Neuroscience, Department of Psychology, University of Oregon, Eugene, OR 97403, USA.
Neuron. 2010 Feb 11;65(3):412-21. doi: 10.1016/j.neuron.2010.01.020.
Neurons in visual, somatosensory, and auditory cortex can respond to the termination as well as the onset of a sensory stimulus. In auditory cortex, these off responses may underlie the ability of the auditory system to use sound offsets as cues for perceptual grouping. Off responses have been widely proposed to arise from postinhibitory rebound, but this hypothesis has never been directly tested. We used in vivo whole-cell recordings to measure the synaptic inhibition evoked by sound onset. We find that inhibition is invariably transient, indicating that off responses are not caused by postinhibitory rebound in auditory cortical neurons. Instead, on and off responses appear to be driven by distinct sets of synapses, because they have distinct frequency tuning and different excitatory-inhibitory balance. Furthermore, an on-on sequence causes complete forward suppression, whereas an off-on sequence causes no suppression at all. We conclude that on and off responses are driven by largely nonoverlapping sets of synaptic inputs.
视觉、体感和听觉皮层中的神经元可以对感觉刺激的终止和开始做出反应。在听觉皮层中，这些负向反应可能是听觉系统利用声音结束作为感知分组线索的基础。负向反应广泛被认为是由抑制后反弹引起的，但这一假设从未被直接验证过。我们使用体内全细胞记录来测量声音起始引起的突触抑制。我们发现抑制总是短暂的，这表明负向反应不是由听觉皮层神经元的抑制后反弹引起的。相反，正向和负向反应似乎是由不同的突触驱动的，因为它们具有不同的频率调谐和不同的兴奋性-抑制性平衡。此外，一个正-正序列会导致完全的前向抑制，而一个负-正序列则根本不会抑制。我们得出结论，正向和负向反应是由很大程度上不重叠的突触输入驱动的。
