New thin-film surface electrode array enables brain mapping with high spatial acuity in rodents

W S Konerding,U P Froriep,P Baumhoff,A Kral

doi:10.1038/s41598-018-22051-z

Abstract

In neuroscience, single-shank penetrating multi-electrode arrays are standard for sequentially sampling several cortical sites with high spatial and temporal resolution, with the disadvantage of neuronal damage. Non-penetrating surface grids used in electrocorticography (ECoG) permit simultaneous recording of multiple cortical sites, with limited spatial resolution, due to distance to neuronal tissue, large contact size and high impedances. Here we compared new thin-film parylene C ECoG grids, covering the guinea pig primary auditory cortex, with simultaneous recordings from penetrating electrode array (PEAs), inserted through openings in the grid material. ECoG grid local field potentials (LFP) showed higher response thresholds and amplitudes compared to PEAs. They enabled, however, fast and reliable tonotopic mapping of the auditory cortex (place-frequency slope: 0.7 mm/octave), with tuning widths similar to PEAs. The ECoG signal correlated best with supragranular layers, exponentially decreasing with cortical depth. The grids also enabled recording of multi-unit activity (MUA), yielding several advantages over LFP recordings, including sharper frequency tunings. ECoG first spike latency showed highest similarity to superficial PEA contacts and MUA traces maximally correlated with PEA recordings from the granular layer. These results confirm high quality of the ECoG grid recordings and the possibility to collect LFP and MUA simultaneously.

Highlights

An important goal in neuroscience is to understand the activation patterns of neuronal networks at a high spatial and temporal resolution
We found that the new ECoG grids were suitable for recording both local field potentials (LFP) at high spatial resolution and multi-unit activity (MUA) comparable to simultaneous recordings from penetrating electrode arrays (PEAs)
We showed the similarity of LFP recordings from the ECoG grid to simultaneously recorded LFP of PEAs

Summary

Introduction

An important goal in neuroscience is to understand the activation patterns of neuronal networks at a high spatial and temporal resolution. The characterization of the spatio-temporal activation patterns in the auditory cortex has commonly been assessed via recordings with penetrating multi-electrode arrays (MEAs), which have the disadvantage of damaging the brain tissue[2]. This is especially disadvantageous for chronic recordings in behaving animals[2,3]. In order to track ongoing changes in a chronic setting, for example after deprivation and following sensory restoration, spatially and temporally precise but non-invasive recording methods are favorable Both local field potentials (LFPs) and action potential related activity are important to understand the complex neuronal responses to sensory stimulation[6].

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Discussion

Conclusion