Dept. of Neurosurgery, The Univ. of Iowa, Iowa City, IA 52242, USA.
J Neurophysiol. 2013 Mar;109(5):1283-95. doi: 10.1152/jn.00718.2012. Epub 2012 Dec 12.
Evidence regarding the functional subdivisions of human auditory cortex has been slow to converge on a definite model. In part, this reflects inadequacies of current understanding of how the cortex represents temporal information in acoustic signals. To address this, we investigated spatiotemporal properties of auditory responses in human posterolateral superior temporal (PLST) gyrus to acoustic click-train stimuli using intracranial recordings from neurosurgical patients. Subjects were patients undergoing chronic invasive monitoring for refractory epilepsy. The subjects listened passively to acoustic click-train stimuli of varying durations (160 or 1,000 ms) and rates (4-200 Hz), delivered diotically via insert earphones. Multicontact subdural grids placed over the perisylvian cortex recorded intracranial electrocorticographic responses from PLST and surrounding areas. Analyses focused on averaged evoked potentials (AEPs) and high gamma (70-150 Hz) event-related band power (ERBP). Responses to click trains featured prominent AEP waveforms and increases in ERBP. The magnitude of AEPs and ERBP typically increased with click rate. Superimposed on the AEPs were frequency-following responses (FFRs), most prominent at 50-Hz click rates but still detectable at stimulus rates up to 200 Hz. Loci with the largest high gamma responses on PLST were often different from those sites that exhibited the strongest FFRs. The data indicate that responses of non-core auditory cortex of PLST represent temporal stimulus features in multiple ways. These include an isomorphic representation of periodicity (as measured by the FFR), a representation based on increases in non-phase-locked activity (as measured by high gamma ERBP), and spatially distributed patterns of activity.
有关人类听觉皮层功能细分的证据一直难以形成明确的模式。部分原因是，目前人们对皮质如何在声信号中表示时间信息的理解还存在不足。为了解决这个问题，我们使用神经外科患者的颅内记录，研究了人类后外侧颞上回（PLST）对声点击列车刺激的时空听觉反应特性。研究对象为接受慢性侵入性监测以治疗难治性癫痫的患者。这些患者被动聆听不同时长（160 或 1000 毫秒）和速率（4-200Hz）的声点击列车刺激，通过插入式耳机以双耳方式传递。置于周围大脑皮层上的多接触硬膜下网格记录来自 PLST 和周围区域的颅内脑电图反应。分析集中在平均诱发电位（AEPs）和高伽马（70-150Hz）事件相关波段功率（ERBP）上。点击列车反应的特征是明显的 AEP 波形和 ERBP 的增加。AEPs 和 ERBP 的幅度通常随点击速率的增加而增加。AEPs 上叠加有频率跟随反应（FFR），在 50Hz 的点击速率下最为明显，但在高达 200Hz 的刺激速率下仍可检测到。在 PLST 上具有最大高伽马反应的部位通常与那些表现出最强 FFR 的部位不同。这些数据表明，PLST 非核心听觉皮层的反应以多种方式代表了时间刺激特征。这些包括周期性的同构表示（如 FFR 所测量）、基于非锁相活动增加的表示（如高伽马 ERBP 所测量），以及空间分布的活动模式。
