Data from: Resolving the mesoscopic missing link: biophysical modeling of EEG from cortical columns in primates

Event-related potentials (ERP) are among the most widely measured indices for studying human cognition. While their timing and magnitude provide valuable insights, their usefulness is limited by our understanding of their neural generators at the circuit level. Inverse source localization offers insights into such generators, but their solutions are not unique. To address this problem, scientists have assumed the source space generating such signals comprises a set of discrete equivalent current dipoles, representing the activity of small cortical regions. Based on this notion, theoretical studies have employed forward modeling of scalp potentials to understand how changes in circuit-level dynamics translate into macroscopic ERPs. However, experimental validation is lacking because it requires in vivo measurements of intracranial brain sources. Laminar local field potentials (LFP) offer a mechanism for estimating intracranial current sources. Yet, a theoretical link between LFPs and intracranial brain sources is missing. Here, we present a forward modeling approach for estimating mesoscopic intracranial brain sources from LFPs and predict their contribution to macroscopic ERPs. We evaluate the accuracy of this LFP-based representation of brain sources utilizing synthetic laminar neurophysiological measurements and then demonstrate the power of the approach in vivo to clarify the source of a representative cognitive ERP component. To that end, LFP was measured across the cortical layers of visual area V4 in macaque monkeys performing an attention demanding task. We show that area V4 generates dipoles through layer-specific transsynaptic currents that biophysically recapitulate the ERP component through the detailed forward modeling. The constraints imposed on EEG production by this method also revealed an important dissociation between computational and biophysical contributors. As such, this approach represents an important bridge between laminar microcircuitry, through the mesoscopic activity of cortical columns to the patterns of EEG we measure at the scalp.

事件相关电位（Event-related potentials, ERP）是当前用于研究人类认知的最广泛应用的指标之一。其时程与幅值可为认知研究提供宝贵洞见，但我们对其环路层面的神经发生器的认知，限制了该技术的应用价值。逆源定位技术可揭示此类发生器的相关信息，但该方法的解并不唯一。为解决这一难题，研究者假设产生这类信号的源空间由一组离散的等效电流偶极子，该偶极子代表小型皮层区域的神经活动。基于这一思路，已有理论研究通过头皮电位正演建模，探究环路层面的动态变化如何转化为宏观事件相关电位。然而，此类研究缺乏实验验证，因为这需要获取颅内脑源的活体测量数据。层状局部场电位（Laminar local field potentials, LFP）为颅内电流源的估算提供了可行途径，但目前仍缺少层状局部场电位与颅内脑源之间的理论关联。本研究提出一种正演建模方法，可从层状局部场电位中估算介观尺度的颅内脑源，并预测其对宏观事件相关电位的贡献。研究团队首先利用合成的层状神经生理学测量数据，评估了基于层状局部场电位的脑源表征的准确性；随后通过活体实验验证了该方法的效能，以阐明典型认知事件相关电位成分的来源。具体而言，研究人员在执行注意力任务的猕猴视觉皮层V4区的各皮层层中采集了层状局部场电位。结果表明，V4区通过层特异性跨突触电流可产生等效电流偶极子，经详细的正演建模后，该偶极子可在生物物理层面重现该认知事件相关电位成分。该方法对脑电图（electroencephalogram, EEG）生成施加的约束条件，还揭示了计算贡献与生物物理贡献之间的重要解离。综上，该方法搭建了一座重要的桥梁：从层状微环路，经由皮层柱的介观活动，最终抵达我们在头皮处测得的脑电图模式。