title: Simultaneous recording of ECoG and intracortical neuronal activity using a flexible multichannel electrode-mesh in visual cortex.
abstract: Electrocorticogram (ECoG) is a well-balanced methodology for stably mapping brain surface local field potentials (LFPs) over a wide cortical region with high signal fidelity and minimal invasiveness to the brain tissue. To directly compare surface ECoG signals with intracortical neuronal activity immediately underneath, we fabricated a flexible multichannel electrode array with mesh-form structure using micro-electro-mechanical systems. A Parylene-C-based "electrode-mesh" for rats contained a 6×6 gold electrode array with 1-mm interval. Specifically, the probe had 800×800 μm(2) fenestrae in interelectrode spaces, through which simultaneous penetration of microelectrode was capable. This electrode-mesh was placed acutely or chronically on the dural/pial surface of the visual cortex of Long-Evans rats for up to 2 weeks. We obtained reliable trial-wise profiles of visually evoked ECoG signals through individual eye stimulation. Visually evoked ECoG signals from the electrode-mesh exhibited as well or larger signal amplitudes as intracortical LFPs and less across-trial variability than conventional silver-ball ECoG. Ocular selectivity of ECoG responses was correlated with that of intracortical spike/LFP activities. Moreover, single-trial ECoG signals carried sufficient information for predicting the stimulated eye with a correct performance approaching 90%, and the decoding was significantly generalized across sessions over 6 hours. Electrode impedance or signal quality did not obviously deteriorate for 2 weeks following implantation. These findings open up a methodology to directly explore ECoG signals with reference to intracortical neuronal sources and would provide a key to developing minimally invasive next-generation brain-machine interfaces.
authors.affiliation: Department of Physiology, Niigata University School of Medicine, Niigata, Japan. toda@med.niigata-u.ac.jp
authors.forename: Haruo
authors.initials: H
authors.lastname: Toda
authors.forename: Takafumi
authors.initials: T
authors.lastname: Suzuki
authors.forename: Hirohito
authors.initials: H
authors.lastname: Sawahata
authors.forename: Kei
authors.initials: K
authors.lastname: Majima
authors.forename: Yukiyasu
authors.initials: Y
authors.lastname: Kamitani
authors.forename: Isao
authors.initials: I
authors.lastname: Hasegawa
mesh_terms: D000818:Animals; D023882:Dominance, Ocular / Q000502:physiology; D004562:Electrocardiography / Q000379:methods*; D004566:Electrodes; D008991:Monitoring, Physiologic / Q000295:instrumentation / Q000379:methods; D009474:Neurons / Q000502:physiology*; D010775:Photic Stimulation; D051381:Rats; D012535:Scalp / Q000502:physiology; D015398:Signal Transduction; D014793:Visual Cortex / Q000502:physiology*; D014794:Visual Fields