The dynamics of information flow within the auditory cortical hierarchy associated with speech processing and the emergence of hemispheric specialization remain incompletely understood. To study these questions with high spatiotemporal resolution, intracranial recordings in 29 human neurosurgical patients of both sexes were obtained while subjects performed a semantic classification task. Neural activity was recorded from posteromedial portion of Heschl's gyrus (HGPM) and anterolateral portion of Heschl's gyrus (HGAL), planum temporale (PT), planum polare, insula, and superior temporal gyrus (STG). Responses to monosyllabic words exhibited early gamma power increases and a later suppression of alpha power, envisioned to represent feedforward activity and decreased feedback signaling, respectively. Gamma activation and alpha suppression had distinct magnitude and latency profiles. HGPM and PT had the strongest gamma responses with shortest onset latencies, indicating that they are the earliest auditory cortical processing stages. The origin of attenuated top-down influences in auditory cortex, as indexed by alpha suppression, was in STG and HGAL. Gamma responses and alpha suppression were typically larger to nontarget words than tones. Alpha suppression was uniformly greater to target versus nontarget stimuli. Hemispheric bias for words versus tones and for target versus nontarget words, when present, was left lateralized. Better task performance was associated with increased gamma activity in the left PT and greater alpha suppression in HGPM and HGAL bilaterally. The prominence of alpha suppression during semantic classification and its accessibility for noninvasive electrophysiologic studies suggests that this measure is a promising index of auditory cortical speech processing.

SIGNIFICANCE STATEMENT Understanding the dynamics of cortical speech processing requires the use of active tasks. This is the first comprehensive intracranial electroencephalography study to examine cortical activity within the superior temporal plane, lateral superior temporal gyrus, and the insula during a semantic classification task. Distinct gamma activation and alpha suppression profiles clarify the functional organization of feedforward and feedback processing within the auditory cortical hierarchy. Asymmetries in cortical speech processing emerge at early processing stages. Relationships between cortical activity and task performance are interpreted in the context of current models of speech processing. Results lay the groundwork for iEEG studies using connectivity measures of the bidirectional information flow within the auditory processing hierarchy.

与语音处理相关的听觉皮层层次结构内的信息流动态以及半球专业化的出现仍然不完全清楚。为了以高时空分辨率研究这些问题，我们在受试者执行语义分类任务时获得了 29 名男女神经外科患者的颅内记录。记录赫施尔回后内侧部分 (HGPM) 和赫施尔回前外侧部分 (HGAL)、颞平面 (PT)、极平面、岛叶和颞上回 (STG) 的神经活动。对单音节单词的反应表现出早期伽马功率的增加和后期阿尔法功率的抑制，预计分别代表前馈活动和反馈信号减少。伽马激活和阿尔法抑制具有不同的幅度和潜伏期曲线。 HGPM 和 PT 具有最强的伽马响应和最短的起始潜伏期，表明它们是最早的听觉皮层处理阶段。以 α 抑制为指标，听觉皮层自上而下影响减弱的根源在于 STG 和 HGAL。非目标词的伽马响应和阿尔法抑制通常比音调更大。目标刺激与非目标刺激的阿尔法抑制一致更大。如果存在的话，单词与语气以及目标词与非目标词的半球偏差是左偏的。更好的任务表现与左侧 PT 的 γ 活性增加以及双侧 HGPM 和 HGAL 的 α 抑制更大有关。 α 抑制在语义分类过程中的重要性及其在无创电生理学研究中的可及性表明，这种测量是听觉皮层语音处理的一个有前途的指标。

意义陈述了解皮层语音处理的动态需要使用主动任务。这是第一个全面的颅内脑电图研究，用于在语义分类任务期间检查颞上平面、颞上回外侧和岛叶内的皮质活动。不同的伽马激活和阿尔法抑制曲线阐明了听觉皮层层次结构中前馈和反馈处理的功能组织。皮层语音处理的不对称性出现在早期处理阶段。皮层活动和任务表现之间的关系是在当前语音处理模型的背景下解释的。结果为使用听觉处理层次结构内双向信息流的连通性测量的 iEEG 研究奠定了基础。