Biology subjects

Kampff, A. R.

Publications and source records attributed to Kampff, A. R..

4 recordsLinked to original sources

bioRxiv2020

Transparent and flexible ECoG electrode arrays based on silver nanowire networks for neural recordings

This work explored hybrid films of silver nanowires (AgNWs) with indium-zinc oxide (IZO) for developing high-performance and low-cost electrocorticography (ECoG) electrodes. The transparent hybrid films achieved a sheet resistance of 6 {Omega}/sq enabling electrodes with 500 m diameter to reach an impedance of 20 k{Omega} at 1 kHz and a charge storage capacity of 3.2 mC/cm2, an improvement in properties over IZO electrodes, whose performance is on par with the classical tin doped indium oxide (ITO). Characterization of light-induced artifacts was performed showing that light intensities <14 mW/mm2 elicit minimal electrical potential variation, which falls within the magnitude of baseline noise. The validation of electrodes in vivo was achieved by recording electrical neural activity from the surface of rat cortex under anaesthesia. Moreover, the presence of the hybrid films did not cause distortion of light during fluorescence microscopy. This study highlighted the capabilities of the hybrid structure of AgNWs with IZO, that can be fabricated with industrially-established processes at low cost, to be used for transparent ECoG electrodes, offering a new way to record neural electrical activity on a large and fast scale with direct visualization of neurons.

neuroscience↗

bioRxiv2020

The lonely fish is not a loner fish: whole-brain mapping reveals abnormal activity in socially isolated zebrafish

The zebrafish is used to assess the impact of social isolation on behaviour and brain function. As in humans and other social species, early social deprivation reduces social preference in juvenile zebrafish. Whole-brain functional maps of anti-social isolated fish were distinct from anti-social fish found in the normal population. These isolation-induced activity changes revealed profound disruption of neural activity in brain areas linked to social behaviour, such as the preoptic area and hypothalamus. Several of these affected regions are modulated by serotonin, and we found that social preference in isolated fish could be rescued by acutely reducing serotonin levels.

neuroscience↗

bioRxiv2018

Why not record from every channel with a CMOS scanning probe?

It is an uninformative truism to state that the brain operates at multiple spatial and temporal scales, each with each own set of emergent phenomena. More worthy of attention is the point that our current understanding of it cannot clearly indicate which of these phenomenological scales are the significant contributors to the brains function and primary output (i.e. behaviour). Apart from the sheer complexity of the problem, a major contributing factor to this state of affairs is the lack of instrumentation that can simultaneously address these multiple scales without causing function altering damages to the underlying tissue. One important facet of this problem is that standard neural recording devices normally require one output connection per electrode. This limits the number of electrodes that can fit along the thin shafts of implantable probes generating a limiting balance between density and spread. Sharing a single output connection between multiple electrodes relaxes this constraint and permits designs of ultra-high density probes. Here we report the design and in-vivo validation of such a device, a complementary metal-oxide-semiconductor (CMOS) scanning probe with 1344 electrodes; the outcome of the European research project NeuroSeeker. We show that this design targets both local and global spatial scales by allowing the simultaneous recording of more than 1000 neurons spanning 7 functional regions with a single shaft. The neurons show similar recording longevity and signal to noise ratio to passive probes of comparable size and no adverse effects in awake or anesthetized animals. Addressing the data management of this device we also present novel visualization and monitoring methods. Using the probe with freely moving animals we show how accessing a number of cortical and subcortical brain regions offers a novel perspective on how the brain operates around salient behavioural events. Finally, we compare this probe with lower density, non CMOS designs (which have to adhere to the one electrode per output line rule). We show that an increase in density results in capturing neural firing patterns, undetectable by lower density devices, which correlate to self-similar structures inherent in complex naturalistic behaviour. To help design electrode configurations for future, even higher density, CMOS probes, recordings from many different brain regions were obtained with an ultra-dense passive probe.

neuroscience↗

bioRxiv2018

Does impedance matter when recording spikes with polytrodes?

Extracellular microelectrodes have been widely used to measure brain activity, yet there are still basic questions about the requirements for a good extracellular microelectrode. One common source of confusion is how an electrodes impedance affects the amplitude of extracellular spikes and background noise.\n\nHere we discuss how an electrodes impedance affects data quality in extracellular recordings, which is crucial for both the detection of spikes and their assignment to the correct neurons. This study employs commercial polytrodes containing 32 electrodes (177 m2) arranged in a dense array. This allowed us to directly compare, side-by-side, the same extracellular signals measured by modified low impedance (~100 kOhm) microelectrodes with unmodified high impedance (~1 MOhm) microelectrodes. We begin with an evaluation of existing protocols to lower the impedance of the electrodes. The poly(3,4-ethylenedioxythiophene)-polystyrene sulfonate (PEDOT-PSS) electrodeposition protocol is a simple, stable, and reliable method for decreasing the impedance of a microelectrode up to tenfold. We next record in vivo using polytrodes that are modified in a chess board pattern, such that the signal of one neuron is detected by multiple coated and non-coated electrodes. The performance of the coated and non-coated electrodes is then compared on measures of background noise and amplitude of the detected action potentials.\n\nIf the proper recording system is used, then the impedance of a microelectrode within the range of standard polytrodes (~ 0.1 to 2 MOhm) does not significantly affect data quality and spike sorting. This study should encourage neuroscientists to stop worrying about one more unknown.

neuroscience↗