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A multimodal micro-optrode combining field and single unit recording, multispectral detection and photolabeling capabilities.

Dufour S, Lavertu G, Dufour-Beauséjour S, Juneau-Fecteau A, Calakos N, Deschênes M, Vallée R, De Koninck Y - PLoS ONE (2013)

Bottom Line: Here, we describe a, aluminum-coated, fibre optic-based glass microprobe with multiple electrical and optical detection capabilities while retaining tip dimensions that enable single cell measurements (diameter ≤10 µm).It also enables color conversion of photoswitchable fluorescent proteins, which can be used for post-hoc identification of the recorded cells.The extended range of functionalities provided by the same microprobe thus opens several avenues for multidimensional structural and functional interrogation of single cells and their surrounding deep within the intact nervous system.

View Article: PubMed Central - PubMed

Affiliation: Unité de neurosciences cellulaires et moléculaires, Institut universitaire en santé mentale de Québec, Québec, Québec, Canada.

ABSTRACT
Microelectrodes have been very instrumental and minimally invasive for in vivo functional studies from deep brain structures. However they are limited in the amount of information they provide. Here, we describe a, aluminum-coated, fibre optic-based glass microprobe with multiple electrical and optical detection capabilities while retaining tip dimensions that enable single cell measurements (diameter ≤10 µm). The probe enables optical separation from individual cells in transgenic mice expressing multiple fluorescent proteins in distinct populations of neurons within the same deep brain nucleus. It also enables color conversion of photoswitchable fluorescent proteins, which can be used for post-hoc identification of the recorded cells. While metal coating did not significantly improve the optical separation capabilities of the microprobe, the combination of metal on the outside of the probe and of a hollow core within the fiber yields a microelectrode enabling simultaneous single unit and population field potential recordings. The extended range of functionalities provided by the same microprobe thus opens several avenues for multidimensional structural and functional interrogation of single cells and their surrounding deep within the intact nervous system.

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Coated glass microprobes enable dual electrical recordings.A) Schematic representation of a multimodal microprobe tip. B) Measured resistance as a function of the uninsulated surface. C) Simultaneous recording of field potential oscillations and single unit achieved with the microprobes. Spikes were computed in a time histogram (C1). Inset: overlay of 10 successive spikes (vertical scale bar: 0.1 mV, horizontal scale bar: 1 ms) (C2) according to time of occurrence relative to field maxima (arrows in c1; n = 15) and into an interspike interval histograms (C3).
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pone-0057703-g006: Coated glass microprobes enable dual electrical recordings.A) Schematic representation of a multimodal microprobe tip. B) Measured resistance as a function of the uninsulated surface. C) Simultaneous recording of field potential oscillations and single unit achieved with the microprobes. Spikes were computed in a time histogram (C1). Inset: overlay of 10 successive spikes (vertical scale bar: 0.1 mV, horizontal scale bar: 1 ms) (C2) according to time of occurrence relative to field maxima (arrows in c1; n = 15) and into an interspike interval histograms (C3).

Mentions: Given the conductive properties of Al, coatings can also serve as field potential electrodes. The detecting surface (uninsulated tip) of these electrodes must be relevant to the size of the region of interest and their resistance must be as small as possible. To characterize probe performances, we measured electrode resistance for different detecting areas. Thin metallic layers may have very high resistances, but the thickness used here (≈ 100 nm) is large enough and has as a negligible effect on the electrode resistance. The resistance is therefore low enough for field potential recordings and can be adjusted as desired by controlling the uninsulated tip surface of the electrode and, as predicted by the Robinson model [9], is inversely proportional to that surface (Fig. 6a, R2 = 0.95, n = 74 electrodes). Microprobes with metal coating resistances ranging from 0.6 to 4 MΩ were used to record simultaneously single unit (through the hollow core) and field potentials during spontaneous activity (n = 28 cells) (Fig. 6c). In Figure 6c, field and single unit recordings show the typical slow wave activity of cortical neurons under ketamine-xylazine anesthesia [10]. Note that this frequency differs from anaesthetized rat respiratory frequency (typically 1 Hz). Figure 6c also shows a histogram where spikes were computed according to the slow field cycles (2–10 Hz) and an interspike interval histogram. Spike occurrence shows a correlation with the field state. This dual recording capability adds new functionality to this type of fibre optic microprobe, including the ability to interrogate the central nervous system both at single cell and network levels concurrently.


A multimodal micro-optrode combining field and single unit recording, multispectral detection and photolabeling capabilities.

Dufour S, Lavertu G, Dufour-Beauséjour S, Juneau-Fecteau A, Calakos N, Deschênes M, Vallée R, De Koninck Y - PLoS ONE (2013)

Coated glass microprobes enable dual electrical recordings.A) Schematic representation of a multimodal microprobe tip. B) Measured resistance as a function of the uninsulated surface. C) Simultaneous recording of field potential oscillations and single unit achieved with the microprobes. Spikes were computed in a time histogram (C1). Inset: overlay of 10 successive spikes (vertical scale bar: 0.1 mV, horizontal scale bar: 1 ms) (C2) according to time of occurrence relative to field maxima (arrows in c1; n = 15) and into an interspike interval histograms (C3).
© Copyright Policy
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC3585187&req=5

pone-0057703-g006: Coated glass microprobes enable dual electrical recordings.A) Schematic representation of a multimodal microprobe tip. B) Measured resistance as a function of the uninsulated surface. C) Simultaneous recording of field potential oscillations and single unit achieved with the microprobes. Spikes were computed in a time histogram (C1). Inset: overlay of 10 successive spikes (vertical scale bar: 0.1 mV, horizontal scale bar: 1 ms) (C2) according to time of occurrence relative to field maxima (arrows in c1; n = 15) and into an interspike interval histograms (C3).
Mentions: Given the conductive properties of Al, coatings can also serve as field potential electrodes. The detecting surface (uninsulated tip) of these electrodes must be relevant to the size of the region of interest and their resistance must be as small as possible. To characterize probe performances, we measured electrode resistance for different detecting areas. Thin metallic layers may have very high resistances, but the thickness used here (≈ 100 nm) is large enough and has as a negligible effect on the electrode resistance. The resistance is therefore low enough for field potential recordings and can be adjusted as desired by controlling the uninsulated tip surface of the electrode and, as predicted by the Robinson model [9], is inversely proportional to that surface (Fig. 6a, R2 = 0.95, n = 74 electrodes). Microprobes with metal coating resistances ranging from 0.6 to 4 MΩ were used to record simultaneously single unit (through the hollow core) and field potentials during spontaneous activity (n = 28 cells) (Fig. 6c). In Figure 6c, field and single unit recordings show the typical slow wave activity of cortical neurons under ketamine-xylazine anesthesia [10]. Note that this frequency differs from anaesthetized rat respiratory frequency (typically 1 Hz). Figure 6c also shows a histogram where spikes were computed according to the slow field cycles (2–10 Hz) and an interspike interval histogram. Spike occurrence shows a correlation with the field state. This dual recording capability adds new functionality to this type of fibre optic microprobe, including the ability to interrogate the central nervous system both at single cell and network levels concurrently.

Bottom Line: Here, we describe a, aluminum-coated, fibre optic-based glass microprobe with multiple electrical and optical detection capabilities while retaining tip dimensions that enable single cell measurements (diameter ≤10 µm).It also enables color conversion of photoswitchable fluorescent proteins, which can be used for post-hoc identification of the recorded cells.The extended range of functionalities provided by the same microprobe thus opens several avenues for multidimensional structural and functional interrogation of single cells and their surrounding deep within the intact nervous system.

View Article: PubMed Central - PubMed

Affiliation: Unité de neurosciences cellulaires et moléculaires, Institut universitaire en santé mentale de Québec, Québec, Québec, Canada.

ABSTRACT
Microelectrodes have been very instrumental and minimally invasive for in vivo functional studies from deep brain structures. However they are limited in the amount of information they provide. Here, we describe a, aluminum-coated, fibre optic-based glass microprobe with multiple electrical and optical detection capabilities while retaining tip dimensions that enable single cell measurements (diameter ≤10 µm). The probe enables optical separation from individual cells in transgenic mice expressing multiple fluorescent proteins in distinct populations of neurons within the same deep brain nucleus. It also enables color conversion of photoswitchable fluorescent proteins, which can be used for post-hoc identification of the recorded cells. While metal coating did not significantly improve the optical separation capabilities of the microprobe, the combination of metal on the outside of the probe and of a hollow core within the fiber yields a microelectrode enabling simultaneous single unit and population field potential recordings. The extended range of functionalities provided by the same microprobe thus opens several avenues for multidimensional structural and functional interrogation of single cells and their surrounding deep within the intact nervous system.

Show MeSH
Related in: MedlinePlus