Abstract
Multielectrode arrays (MEAs) allow for acquisition of multisite electrophysiological activity with submillisecond temporal resolution from neural preparations. The signal to noise ratio from such arrays has recently been improved by substrate perforations that allow negative pressure to be applied to the tissue; however, such arrays are not optically transparent, limiting their potential to be combined with optical-based technologies. We present here multi-suction electrode arrays (MSEAs) in quartz that yield a substantial increase in the detected number of units and in signal to noise ratio from mouse cortico-hippocampal slices and mouse retina explants. This enables the visualization of stronger cross correlations between the firing rates of the various sources. Additionally, the MSEA's transparency allows us to record voltage sensitive dye activity from a leech ganglion with single neuron resolution using widefield microscopy simultaneously with the electrode array recordings. The combination of enhanced electrical signals and compatibility with optical-based technologies should make the MSEA a valuable tool for investigating neuronal circuits.
Highlights
Multielectrode arrays (MEAs, Gross et al, 1977; Gross, 1979; Pine, 1980; Obien et al, 2014) have successfully been used to study a range of preparations including dissociated cortical cultures (Wagenaar et al, 2006), retinal explants (Meister et al, 1991), and hippocampal slices (Steidl et al, 2006)
We demonstrate the practical utility of these multi-suction electrode arrays (MSEAs) firstly by recording from mouse cortico-hippocampal slices, in which suction resulted in a dramatic increase in signal-to-noise ratio of recorded spikes and a concomitant increase in the number of detectable units
We tested our MSEAs with three distinct preparations: cortico-hippocampal slices from mice, explanted mouse retinae, and isolated leech ganglia to determine, first of all, whether neuronal activity could be observed successfully, and secondly, whether applying suction made a difference to the quality of the recordings
Summary
Multielectrode arrays (MEAs, Gross et al, 1977; Gross, 1979; Pine, 1980; Obien et al, 2014) have successfully been used to study a range of preparations including dissociated cortical cultures (Wagenaar et al, 2006), retinal explants (Meister et al, 1991), and hippocampal slices (Steidl et al, 2006). Obtaining strong voltage signals from most of these preparations is possible, but slices continue to pose challenges, likely because of the presence of a layer of dead cells at the surface of the slice and limited oxygenation through the slice to the living cells nearest to the array. The introduction of perforated MEAs in polyimide is an improvement in regard to tissue oxygenation and signal to noise ratio, but has limitations: Whereas glass-based MEAs are transparent (except for the electrodes and sometimes the leads) (Gross et al, 1985), presently available commercial perforated MEAs are not due to the translucent polyimide substrate (Egert et al, 2005). Polyimide was preferred as the substrate for perforated MEAs because of the relative ease of creating micrometer-sized perforations in an organic substrate vs a glass-based substrate (Egert et al, 2005). Recent material processing advances in our lab have allowed for the fabrication of thinned, optically transparent suspended membranes and though-hole arrays
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