Halgren Eric, Wang Chunmao, Schomer Donald L, Knake Susanne, Marinkovic Ksenija, Wu Julian, Ulbert Istvan
Multimodal Imaging Laboratory, Department of Radiology, University of California at San Diego, La Jolla, CA 92093-0841, USA.
Neuroimage. 2006 May 1;30(4):1401-13. doi: 10.1016/j.neuroimage.2005.10.053. Epub 2006 Feb 17.
The anteroventral temporal lobe integrates visual, lexical, semantic and mnestic aspects of word processing, through its reciprocal connections with the ventral visual stream, language areas, and the hippocampal formation. We used linear microelectrode arrays to probe population synaptic currents and neuronal firing in different cortical layers of the anteroventral temporal lobe, during semantic judgments with implicit priming and overt word recognition. Since different extrinsic and associative inputs preferentially target different cortical layers, this method can help reveal the sequence and nature of local processing stages at a higher resolution than was previously possible. The initial response in inferotemporal and perirhinal cortices is a brief current sink beginning at approximately 120 ms and peaking at approximately 170 ms. Localization of this initial sink to middle layers suggests that it represents feedforward input from lower visual areas, and simultaneously increased firing implies that it represents excitatory synaptic currents. Until approximately 800 ms, the main focus of transmembrane current sinks alternates between middle and superficial layers, with the superficial focus becoming increasingly dominant after approximately 550 ms. Since superficial layers are the target of local and feedback associative inputs, this suggests an alternation in predominant synaptic input between feedforward and feedback modes. Word repetition does not affect the initial perirhinal and inferotemporal middle layer sink but does decrease later activity. Entorhinal activity begins later (approximately 200 ms), with greater apparent excitatory post-synaptic currents and multiunit activity in neocortically projecting than hippocampal-projecting layers. In contrast to perirhinal and entorhinal responses, entorhinal responses are larger to repeated words during memory retrieval. These results identify a sequence of physiological activation, beginning with a sharp activation from lower level visual areas carrying specific information to middle layers. This is followed by feedback and associative interactions involving upper cortical layers, which are abbreviated to repeated words. Following bottom-up and associative stages, top-down recollective processes may be driven by entorhinal cortex. Word processing involves a systematic sequence of fast feedforward information transfer from visual areas to anteroventral temporal cortex followed by prolonged interactions of this feedforward information with local associations and feedback mnestic information from the medial temporal lobe.
前腹侧颞叶通过与腹侧视觉通路、语言区域和海马结构的相互连接，整合了单词处理的视觉、词汇、语义和记忆方面。我们使用线性微电极阵列，在进行语义判断（伴有内隐启动和公开单词识别）期间，探测前腹侧颞叶不同皮质层的群体突触电流和神经元放电。由于不同的外在和联想输入优先靶向不同的皮质层，这种方法能够以比以往更高的分辨率，帮助揭示局部处理阶段的顺序和性质。颞下皮质和嗅周皮质的初始反应是一个短暂的电流下沉，始于约120毫秒，在约170毫秒达到峰值。这个初始下沉定位于中层，表明它代表来自较低视觉区域的前馈输入，同时放电增加意味着它代表兴奋性突触电流。直到约800毫秒，跨膜电流下沉的主要焦点在中层和浅层之间交替，在约550毫秒后浅层焦点变得越来越占主导。由于浅层是局部和反馈联想输入的靶点，这表明在前馈和反馈模式之间，主要突触输入存在交替。单词重复不影响初始的嗅周和颞下中层下沉，但会降低后期活动。内嗅活动开始较晚（约200毫秒），在新皮质投射层中，明显的兴奋性突触后电流和多单位活动比海马投射层更大。与嗅周和内嗅反应相反，在记忆检索期间，内嗅对重复单词的反应更大。这些结果确定了一系列生理激活过程，始于携带特定信息的较低水平视觉区域向中层的急剧激活。随后是涉及上层皮质层的反馈和联想相互作用，这些相互作用在重复单词时会缩短。在自下而上和联想阶段之后，自上而下的回忆过程可能由内嗅皮质驱动。单词处理涉及从视觉区域到前腹侧颞叶的快速前馈信息传递的系统序列，随后是该前馈信息与来自内侧颞叶的局部联想和反馈记忆信息的长时间相互作用。
