Large-scale, high-resolution electrophysiological imaging of field potentials in brain slices with microelectronic multielectrode arrays

Multielectrode arrays (MEAs) are extensively used for electrophysiological studies on brain slices, but the spatial resolution and field of recording of conventional arrays are limited by the low number of electrodes available. Here, we present a large-scale array recording simultaneously from 4096 electrodes used to study propagating spontaneous and evoked network activity in acute murine cortico-hippocampal brain slices at unprecedented spatial and temporal resolution. We demonstrate that multiple chemically induced epileptiform episodes in the mouse cortex and hippocampus can be classified according to their spatio-temporal dynamics. Additionally, the large-scale and high-density features of our recording system enable the topological localization and quantification of the effects of antiepileptic drugs in local neuronal microcircuits, based on the distinct field potential propagation patterns. This novel high-resolution approach paves the way to detailed electrophysiological studies in brain circuits spanning spatial scales from single neurons up to the entire slice network.

Tracking burst patterns in hippocampal cultures with high-density CMOS-MEAs

In this work, we investigate the spontaneous bursting behaviour expressed by in vitro hippocampal networks by using a high-resolution CMOS-based microelectrode array (MEA), featuring 4096 electrodes, inter-electrode spacing of 21 µm and temporal resolution of 130 µs. In particular, we report an original development of an adapted analysis method enabling us to investigate spatial and temporal patterns of activity and the interplay between successive network bursts (NBs). We first defined and detected NBs, and then, we analysed the spatial and temporal behaviour of these events with an algorithm based on the centre of activity trajectory. We further refined the analysis by using a technique derived from statistical mechanics, capable of distinguishing the two main phases of NBs, i.e. (i) a propagating and (ii) a reverberating phase, and by classifying the trajectory patterns. Finally, this methodology was applied to signal representations based on spike detection, i.e. the instantaneous firing rate, and directly based on voltage-coded raw data, i.e. activity movies. Results highlight the potentialities of this approach to investigate fundamental issues on spontaneous neuronal dynamics and suggest the hypothesis that neurons operate in a sort of 'team' to the perpetuation of the transmission of the same information.

Reliability of kinematic parameters during unilateral upper limb reaching tasks using a portable motion tracking system

The reliability of a portable computer based system (Motor Task Manager; MTM) used for the assessment of motor dysfunction needs to be assessed before being used clinically. Nine healthy males, aged 24-55 years (mean = 31.4, SD +/- 9.84) performed three unilateral MTM-prescribed reaching task paradigms. Tasks were completed three times in random order during three separate testing sessions. Speed characteristics showed excellent (Intra-class correlation coefficient; ICC 0.78-0.92) and inter-session (ICC 0.86-0.92) reliability for all three tasks. Temporal parameters had fair to good reliability in the first session (ICC 0.42-0.78) which improved in sessions 2 and 3 (ICC 0.64-0.96). Inter-session reliability for temporal characteristics was better for movement time (ICC 0.57-0.84) than onset time (ICC 0.14-0.53). Spatial characteristics demonstrated poor intra- (ICC -0.09-0.63) and inter-sessions (ICC 0.15-0.61) reliability. Speed characteristics were the most robust results for the healthy population studied and recommended for measuring performance, particularly if only one test session is possible.

High-resolution MEA platform for in-vitro electrogenic cell networks imaging

A platform based on an active-pixel-sensor electrode array (APS-MEA) for high-resolution imaging of in-vitro electrogenic cell cultures is presented, characterized and validated under culture conditions. The system enables full frame acquisition at 8 kHz from 4096 microelectrodes integrated with separations of 21 microm and zoomed area acquisition with temporal resolutions down to 8 micros. This bi-modal acquisition feature opens new perspectives in particular for neuronal activity analysis and for the correlation of micro-scale and macro-scale behaviors. The low-noise performances of the integrated amplifier (11 microVRMS) combined with a hardware implementation reflecting image-/video-concepts enable high-resolution acquisitions with real-time processing capabilities adapted to the handling of the large amount of acquired data.