Department of Biomedical Engineering, Duke University, Durham, NC, United States of America. These authors contributed equally to this work.
J Neural Eng. 2020 Jul 10;17(4):046008. doi: 10.1088/1741-2552/ab9986.
A fundamental goal of the auditory system is to parse the auditory environment into distinct perceptual representations. Auditory perception is mediated by the ventral auditory pathway, which includes the ventrolateral prefrontal cortex (vlPFC). Because large-scale recordings of auditory signals are quite rare, the spatiotemporal resolution of the neuronal code that underlies vlPFC's contribution to auditory perception has not been fully elucidated. Therefore, we developed a modular, chronic, high-resolution, multi-electrode array system with long-term viability in order to identify the information that could be decoded from μECoG vlPFC signals.
We molded three separate μECoG arrays into one and implanted this system in a non-human primate. A custom 3D-printed titanium chamber was mounted on the left hemisphere. The molded 294-contact μECoG array was implanted subdurally over the vlPFC. μECoG activity was recorded while the monkey participated in a 'hearing-in-noise' task in which they reported hearing a 'target' vocalization from a background 'chorus' of vocalizations. We titrated task difficulty by varying the sound level of the target vocalization, relative to the chorus (target-to-chorus ratio, TCr).
We decoded the TCr and the monkey's behavioral choices from the μECoG signal. We analyzed decoding accuracy as a function of number of electrodes, spatial resolution, and time from implantation. Over a one-year period, we found significant decoding with individual electrodes that increased significantly as we decoded simultaneously more electrodes. Further, we found that the decoding for behavioral choice was better than the decoding of TCr. Finally, because the decoding accuracy of individual electrodes varied on a day-by-day basis, electrode arrays with high channel counts ensure robust decoding in the long term.
Our results demonstrate the utility of high-resolution and high-channel-count, chronic µECoG recording. We developed a surface electrode array that can be scaled to cover larger cortical areas without increasing the chamber footprint.
听觉系统的一个基本目标是将听觉环境分解为不同的感知表示。听觉感知是由腹侧听觉通路介导的，其中包括腹外侧前额叶皮层（vlPFC）。由于对听觉信号的大规模记录相当罕见，因此尚未完全阐明支持 vlPFC 对听觉感知贡献的神经元编码的时空分辨率。因此，我们开发了一种模块化、慢性、高分辨率、多电极阵列系统，具有长期生存能力，以便识别可以从 μECoG vlPFC 信号中解码的信息。
我们将三个独立的 μECoG 阵列模制成一个，并将该系统植入一只非人类灵长类动物体内。一个定制的 3D 打印钛室安装在左半球上。植入硬膜下的模制 294 个触点 μECoG 阵列位于 vlPFC 上方。当猴子参与“听噪声”任务并报告听到背景“合唱”中的“目标”发声时，记录 μECoG 活动。我们通过改变目标发声相对于合唱的声音水平（目标-合唱比，TCr）来调整任务难度。
我们从 μECoG 信号中解码 TCr 和猴子的行为选择。我们分析了解码精度作为电极数量、空间分辨率和植入时间的函数。在一年的时间里，我们发现单个电极的解码效果显著，随着我们同时解码更多电极，解码效果显著增加。此外，我们发现行为选择的解码效果优于 TCr 的解码效果。最后，由于单个电极的解码精度每天都在变化，因此具有高通道计数的电极阵列可以确保长期稳健的解码。
我们的结果证明了高分辨率和高通道数、慢性 μECoG 记录的实用性。我们开发了一种表面电极阵列，可以扩展到更大的皮层区域，而不会增加腔室足迹。
