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Stimulus-dependent Spiking Relationships with the Eeg. University of Pittsburgh Eye and Ear Institute Abbreviated Title: Spike-eeg Relationships

31 The development and refinement of non-invasive techniques for imaging neural activity 32 is of paramount importance for human neuroscience. Currently, the most accessible and popular 33 technique is electroencephalography (EEG). However, nearly all of what we know about the 34 neural events that underlie EEG signals is based on inference, due to a dearth of studies that 35 simultaneously paired EEG recordings with direct recordings of single neurons. From the 36 perspective of electrophysiologists there is growing interest in understanding how spiking 37 activity coordinates with large-scale cortical networks. Evidence from recordings at both scales 38 highlights that sensory neurons operate in very distinct states during spontaneous and visually 39 evoked activity, which appear to form extremes in a continuum of coordination in neural 40 networks. We hypothesized that individual neurons have idiosyncratic relationships to large41 scale network activity indexed by EEG signals, owing to the neurons’ distinct computational 42 roles within the local circuitry. We tested this by recording neuronal populations in visual area 43 V4 of rhesus macaques while we simultaneously recorded EEG. We found substantial 44 heterogeneity in the timing and strength of spike-EEG relationships, and that these relationships 45 became more diverse during visual stimulation compared to the spontaneous state. The visual 46 stimulus apparently shifts V4 neurons from a state in which they are relatively uniformly 47 embedded in large-scale network activity to a state in which their distinct roles within the local 48 population are more prominent, and suggests that the specific way in which individual neurons 49 relate to EEG signals may hold clues regarding their computational roles. 50