Department of Psychology, University of Pittsburgh, Pittsburgh, Pennsylvania 15213.
Movement Disorder and Neuromodulation Unit, Department of Neurology, Campus Mitte, Charité, Universitätsmedizin Berlin, Berlin, Germany 10117.
J Neurosci. 2019 Apr 3;39(14):2698-2708. doi: 10.1523/JNEUROSCI.2842-18.2019. Epub 2019 Jan 30.
The sensorimotor cortex is somatotopically organized to represent the vocal tract articulators such as lips, tongue, larynx, and jaw. How speech and articulatory features are encoded at the subcortical level, however, remains largely unknown. We analyzed LFP recordings from the subthalamic nucleus (STN) and simultaneous electrocorticography recordings from the sensorimotor cortex of 11 human subjects (1 female) with Parkinson's disease during implantation of deep-brain stimulation (DBS) electrodes while they read aloud three-phoneme words. The initial phonemes involved either articulation primarily with the tongue (coronal consonants) or the lips (labial consonants). We observed significant increases in high-gamma (60-150 Hz) power in both the STN and the sensorimotor cortex that began before speech onset and persisted for the duration of speech articulation. As expected from previous reports, in the sensorimotor cortex, the primary articulators involved in the production of the initial consonants were topographically represented by high-gamma activity. We found that STN high-gamma activity also demonstrated specificity for the primary articulator, although no clear topography was observed. In general, subthalamic high-gamma activity varied along the ventral-dorsal trajectory of the electrodes, with greater high-gamma power recorded in the dorsal locations of the STN. Interestingly, the majority of significant articulator-discriminative activity in the STN occurred before that in sensorimotor cortex. These results demonstrate that articulator-specific speech information is contained within high-gamma activity of the STN, but with different spatial and temporal organization compared with similar information encoded in the sensorimotor cortex. Clinical and electrophysiological evidence suggest that the subthalamic nucleus (STN) is involved in speech; however, this important basal ganglia node is ignored in current models of speech production. We previously showed that STN neurons differentially encode early and late aspects of speech production, but no previous studies have examined subthalamic functional organization for speech articulators. Using simultaneous LFP recordings from the sensorimotor cortex and the STN in patients with Parkinson's disease undergoing deep-brain stimulation surgery, we discovered that STN high-gamma activity tracks speech production at the level of vocal tract articulators before the onset of vocalization and often before related cortical encoding.
躯体感觉运动皮层按照代表声道发音器官(如唇、舌、喉和颌)的方式进行躯体定位。然而,言语和发音特征在皮质下水平是如何编码的,在很大程度上仍然未知。我们分析了 11 名帕金森病患者(1 名女性)在植入深部脑刺激(DBS)电极时,丘脑底核(STN)的局部场电位(LFP)记录和传感器运动皮层的同时皮层电图记录,这些患者在大声朗读三音词时。最初的音素要么主要与舌(冠状辅音)或唇(唇辅音)发音有关。我们观察到 STN 和传感器运动皮层中的高伽马(60-150 Hz)功率显著增加,这种增加始于言语开始之前,并持续到言语发音的整个过程。与之前的报告一致,在传感器运动皮层中,参与初始辅音产生的主要发音器官被高伽马活动以拓扑方式表示。我们发现,尽管没有观察到明确的拓扑结构,但 STN 的高伽马活动也表现出对主要发音器官的特异性。一般来说,STN 的高伽马活动沿着电极的腹侧-背侧轨迹变化,在 STN 的背侧位置记录到更高的高伽马功率。有趣的是,STN 中大多数与发音器相关的显著区分活动发生在传感器运动皮层之前。这些结果表明,发音器特异性言语信息包含在 STN 的高伽马活动中,但与传感器运动皮层中编码的类似信息相比,具有不同的空间和时间组织。临床和电生理证据表明,丘脑底核(STN)参与言语;然而,当前的言语产生模型忽略了这个重要的基底节节点。我们之前曾表明,STN 神经元对言语产生的早期和晚期方面进行了不同的编码,但以前没有研究检查过 STN 对言语发音器的功能组织。使用帕金森病患者在接受深部脑刺激手术时来自传感器运动皮层和 STN 的同步 LFP 记录,我们发现 STN 高伽马活动在发声前跟踪声道发音器的言语产生水平,并且通常在相关皮质编码之前。