An ultra-compact integrated system for brain activity recording and stimulation validated over cortical slow oscillations in vivo and in vitro

Abstract

The understanding of brain processing requires monitoring and exogenous modulation of neuronal ensembles. To this end, it is critical to implement equipment that ideally provides highly accurate, low latency recording and stimulation capabilities, that is functional for different experimental preparations and that is highly compact and mobile. To address these requirements, we designed a small ultra-flexible multielectrode array and combined it with an ultra-compact electronic system. The device consists of a polyimide microelectrode array (8 µm thick and with electrodes measuring as low as 10 µm in diameter) connected to a miniaturized electronic board capable of amplifying, filtering and digitalizing neural signals and, in addition, of stimulating brain tissue. To evaluate the system, we recorded slow oscillations generated in the cerebral cortex network both from in vitro slices and from in vivo anesthetized animals, and we modulated the oscillatory pattern by means of electrical and visual stimulation. Finally, we established a preliminary closed-loop algorithm in vitro that exploits the low latency of the electronics (<0.5 ms), thus allowing monitoring and modulating emergent cortical activity in real time to a desired target oscillatory frequency.

A Glial‐Silicon Nanowire Electrode Junction Enabling Differentiation and Noninvasive Recording of Slow Oscillations from Primary Astrocytes

“…The spontaneous activity of astrocytes was collected by a custom recording system called NeuroDaq based on INTAN chip. Neurodaq consists of an ultra‐compact 32‐channel board, that can amplify, filter and digitized the signal and that can be placed very close to the signal source, thus further lowering the noise level 50. The signal was collected over a frequency range between 0.1 Hz and 10 kHz by using standard saline solution for electrophysiological recording and Ag/AgCl as a reference electrode.…”

Analysis Pipeline for Extracting Features of Cortical Slow Oscillations

“…The multi-electrode array (MEA) employed for acquiring the data is described in Figure 1 and covers several cortical areas ranging from sensory (V1, S1), motor (M1), and association (PtA) cortices (Pazzini et al, 2018). The unfiltered field potential (UFP) is sampled from each electrode at a frequency of 5 kHz and each acquisition session lasts at least 300 s (see Table 1), thus ensuring a fine inspection of the signal in both space and time.…”

“…Representation of the multi-electrode array (MEA) used for the data acquisition (Pazzini et al, 2018), with the numbering introduced in the SWAP. On the top left, a scheme that indicates the scale of the experiment; the reported dimensions have been adopted to define the reference frame in the pipeline.…”

Conductive Polymer Hydrogel Microfibers from Multiflow Microfluidics

“…In this process, PSS unit is partly removed from PEDOT: PSS, and the conformation of PEDOT unit changes from a random coil to an expanded‐coil structure so that the conjugated lengths of PEDOT chains increase greatly, thus the conductivity of PEDOT is increased. Based on these improvements, conductive PEDOT polymers have been fabricated into various shapes at large scale, such as blocks, films, and fibers, for various applications, including light‐emitting diodes, sensors, field‐effect transistors, supercapacitors, and so on . Although with many successes, conductive PEDOT polymers usually lack controllable tailoring and precise control of morphologies and structures at micro scales, which limit their practical value in the manipulation of flexible electronic on microstructures.…”