Cognitive Brain Dynamics Lab, National Brain Research Centre, Gurgaon, Haryana 122052, India.
Brain Imaging and Modeling Section, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Bethesda MD 20892.
eNeuro. 2018 Jul 3;5(3). doi: 10.1523/ENEURO.0420-17.2018. eCollection 2018 May-Jun.
Animals and humans rapidly detect specific features of sounds, but the time courses of the underlying neural response for different stimulus categories is largely unknown. Furthermore, the intricate functional organization of auditory information processing pathways is poorly understood. Here, we computed neuronal response latencies from simultaneously recorded spike trains and local field potentials (LFPs) along the first two stages of cortical sound processing, primary auditory cortex (A1) and lateral belt (LB), of awake, behaving macaques. Two types of response latencies were measured for spike trains as well as LFPs: (1) onset latency, time-locked to onset of external auditory stimuli; and (2) selection latency, time taken from stimulus onset to a selective response to a specific stimulus category. Trial-by-trial LFP onset latencies predominantly reflecting synaptic input arrival typically preceded spike onset latencies, assumed to be representative of neuronal output indicating that both areas may receive input environmental signals and relay the information to the next stage. In A1, simple sounds, such as pure tones (PTs), yielded shorter spike onset latencies compared to complex sounds, such as monkey vocalizations ("Coos"). This trend was reversed in LB, indicating a hierarchical functional organization of auditory cortex in the macaque. LFP selection latencies in A1 were always shorter than those in LB for both PT and Coo reflecting the serial arrival of stimulus-specific information in these areas. Thus, chronometry on spike-LFP signals revealed some of the effective neural circuitry underlying complex sound discrimination.
动物和人类能够迅速察觉声音的特定特征，但对于不同刺激类别的潜在神经反应的时间进程在很大程度上还不清楚。此外，听觉信息处理途径的复杂功能组织也知之甚少。在这里，我们在清醒、行为的猕猴的皮质声音处理的前两个阶段（初级听觉皮层（A1）和外侧带（LB））同时记录的尖峰和局部场电位（LFPs）中计算了神经元反应潜伏期。对于尖峰和 LFPs，我们测量了两种类型的反应潜伏期：（1）起始潜伏期，与外部听觉刺激的起始时间锁定；（2）选择潜伏期，从刺激起始到对特定刺激类别的选择性反应所需的时间。LFPs 起始潜伏期主要反映突触输入的到达，通常先于尖峰起始潜伏期，这被认为是神经元输出的代表，表明这两个区域都可能接收环境信号输入，并将信息传递到下一个阶段。在 A1 中，简单的声音，如纯音（PTs），与复杂的声音，如猴子的叫声（“Coos”）相比，产生的尖峰起始潜伏期更短。这种趋势在 LB 中相反，表明猕猴听觉皮层的功能组织具有分层结构。对于 PT 和 Coo，A1 中的 LFP 选择潜伏期始终短于 LB，这反映了这些区域中刺激特异性信息的串行到达。因此，尖峰-LFP 信号的计时揭示了复杂声音辨别背后的一些有效神经回路。
