Halgren Eric, Kaestner Erik, Marinkovic Ksenija, Cash Sydney S, Wang Chunmao, Schomer Donald L, Madsen Joseph R, Ulbert Istvan
Departments of Radiology and Neurosciences, University of California at San Diego, La Jolla, CA 92069, USA.
Interdepartmental Neurosciences Program, University of California at San Diego, La Jolla, CA 92069, USA.
Neuropsychologia. 2015 Sep;76:108-24. doi: 10.1016/j.neuropsychologia.2015.03.021. Epub 2015 Mar 20.
Theta may play a central role during language understanding and other extended cognitive processing, providing an envelope for widespread integration of participating cortical areas. We used linear microelectrode arrays in epileptics to define the circuits generating theta in inferotemporal, perirhinal, entorhinal, prefrontal and anterior cingulate cortices. In all locations, theta was generated by excitatory current sinks in middle layers which receive predominantly feedforward inputs, alternating with sinks in superficial layers which receive mainly feedback/associative inputs. Baseline and event-related theta were generated by indistinguishable laminar profiles of transmembrane currents and unit-firing. Word presentation could reset theta phase, permitting theta to contribute to late event-related potentials, even when theta power decreases relative to baseline. Limited recordings during sentence reading are consistent with rhythmic theta activity entrained by a given word modulating the neural background for the following word. These findings show that theta occurs spontaneously, and can be momentarily suppressed, reset and synchronized by words. Theta represents an alternation between feedforward/divergent and associative/convergent processing modes that may temporally organize sustained processing and optimize the timing of memory formation. We suggest that words are initially encoded via a ventral feedforward stream which is lexicosemantic in the anteroventral temporal lobe; its arrival may trigger a widespread theta rhythm which integrates the word within a larger context.
θ波可能在语言理解及其他扩展认知加工过程中发挥核心作用，为参与其中的皮质区域的广泛整合提供一个框架。我们在癫痫患者中使用线性微电极阵列来确定在颞下回、嗅周皮质、内嗅皮质、前额叶皮质和前扣带回皮质中产生θ波的神经回路。在所有部位，θ波由中层的兴奋性电流汇产生，中层主要接收前馈输入，与主要接收反馈/联合输入的表层电流汇交替出现。基线θ波和事件相关θ波由跨膜电流和单位放电的难以区分的层状分布产生。单词呈现可重置θ波相位，即使θ波功率相对于基线下降，也能使θ波对晚期事件相关电位产生影响。句子阅读期间的有限记录与由给定单词夹带的节律性θ波活动一致，该活动调节后续单词的神经背景。这些发现表明，θ波是自发出现的，并且可以被单词瞬间抑制、重置和同步。θ波代表前馈/发散和联合/收敛加工模式之间的交替，这可能在时间上组织持续加工并优化记忆形成的时机。我们认为，单词最初通过腹侧前馈流进行编码，该流在颞叶前腹侧是词汇语义性的；其到达可能会触发广泛的θ波节律，将单词整合到更大的语境中。
