EEG inverse source localization methods have offered a tool to estimate plausible brain sources generating such signals and, hence, make inferences about the underlying cortical mechanisms ( Grech et al., 2008 Michel et al., 2004). As such, researchers are developing methods to extract as much information regarding the neural sources of EEG to strengthen this staple of neuroscientific approaches. While the macroscopic EEG contains information, some of it is lost relative to the microscopic activations it reflects. However, some insights into the mechanisms of these neural operations are invisible through this method. Many basic and clinical research programs rely on EEG as a window into human sensation, perception, cognition, and action. Identifying the neural sources of EEG is a substantial challenge facing the human neuroscience community. 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. The constraints imposed on EEG production by this method also revealed an important dissociation between computational and biophysical contributors. We show that area V4 generates dipoles through layer-specific transsynaptic currents that biophysically recapitulate the ERP component through the detailed forward modeling. To that end, LFP was measured across the cortical layers of visual area V4 in macaque monkeys performing an attention demanding task. 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. Here, we present a forward modeling approach for estimating mesoscopic intracranial brain sources from LFPs and predict their contribution to macroscopic ERPs. Yet, a theoretical link between LFPs and intracranial brain sources is missing. Laminar local field potentials (LFP) offer a mechanism for estimating intracranial current sources. However, experimental validation is lacking because it requires in vivo measurements of intracranial brain sources. 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. 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. Inverse source localization offers insights into such generators, but their solutions are not unique. While their timing and magnitude provide valuable insights, their usefulness is limited by our understanding of their neural generators at the circuit level. Event-related potentials (ERP) are among the most widely measured indices for studying human cognition.
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