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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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Related in: MedlinePlus

Side acceptance of tapered waveguides.A) 2D schematic representation of ray acceptance within a tapered waveguide (thick black boundaries). Note that for visualization purpose the taper angle was exaggerated in this illustration. B) Critical accepted incidence angle θ1c as a function of the taper angle θ. Rays with incidence angles ranging from θ1c to 90° will be accepted in the waveguide (parameters were fixed as follows: R = 100 µm, Rf = 5 µm, rc = 60 µm, rcf = 3 µm, n0 = 1 (air), n0 = 1.35 (tissue) n1 = 1.47 and n2 = 1.45).
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pone-0057703-g004: Side acceptance of tapered waveguides.A) 2D schematic representation of ray acceptance within a tapered waveguide (thick black boundaries). Note that for visualization purpose the taper angle was exaggerated in this illustration. B) Critical accepted incidence angle θ1c as a function of the taper angle θ. Rays with incidence angles ranging from θ1c to 90° will be accepted in the waveguide (parameters were fixed as follows: R = 100 µm, Rf = 5 µm, rc = 60 µm, rcf = 3 µm, n0 = 1 (air), n0 = 1.35 (tissue) n1 = 1.47 and n2 = 1.45).

Mentions: Tapered waveguides can collect light through their wall with an acceptance angle that varies with the taper angle θ. Wall collection is less effective per surface area than tip collection, but the surface of the tapered region is significantly larger than the tip transversal surface. Figure 4 illustrates light behavior as a ray is incident on the wall of a tapered waveguide. θ and α are the half angles of the cladding and core tapers. They are determined with the taper length L as well as the initial (R and rc) and final (Rf and rcf) dimensions of the waveguide. These parameters are defined in Figure 4. The ray encounters four interfaces with incidence angles θ1, θ2, θ3 and θ4 respectively. The refractive index of the external medium, the waveguide core and cladding are defined as n0, n1 and n2. For small incidence angle θ1 the ray will be transmitted through the tapered waveguide, but for large θ1, the ray will undergoes total internal reflection at the interface between the waveguide core and the cladding (if θ1 is big enough) or at the interface between the cladding and the external medium. In the later case, the ray will be first guided in the cladding, and after few reflections its incidence angle in the waveguide core will fulfill the total internal reflection requirement of the core. From Snell-Descartes law we can calculate the critical angle θ4c at the interface between the cladding and the external medium and evaluate the angle θ1c that will lead to that critical angle.


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)

Side acceptance of tapered waveguides.A) 2D schematic representation of ray acceptance within a tapered waveguide (thick black boundaries). Note that for visualization purpose the taper angle was exaggerated in this illustration. B) Critical accepted incidence angle θ1c as a function of the taper angle θ. Rays with incidence angles ranging from θ1c to 90° will be accepted in the waveguide (parameters were fixed as follows: R = 100 µm, Rf = 5 µm, rc = 60 µm, rcf = 3 µm, n0 = 1 (air), n0 = 1.35 (tissue) n1 = 1.47 and n2 = 1.45).
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3585187&req=5

pone-0057703-g004: Side acceptance of tapered waveguides.A) 2D schematic representation of ray acceptance within a tapered waveguide (thick black boundaries). Note that for visualization purpose the taper angle was exaggerated in this illustration. B) Critical accepted incidence angle θ1c as a function of the taper angle θ. Rays with incidence angles ranging from θ1c to 90° will be accepted in the waveguide (parameters were fixed as follows: R = 100 µm, Rf = 5 µm, rc = 60 µm, rcf = 3 µm, n0 = 1 (air), n0 = 1.35 (tissue) n1 = 1.47 and n2 = 1.45).
Mentions: Tapered waveguides can collect light through their wall with an acceptance angle that varies with the taper angle θ. Wall collection is less effective per surface area than tip collection, but the surface of the tapered region is significantly larger than the tip transversal surface. Figure 4 illustrates light behavior as a ray is incident on the wall of a tapered waveguide. θ and α are the half angles of the cladding and core tapers. They are determined with the taper length L as well as the initial (R and rc) and final (Rf and rcf) dimensions of the waveguide. These parameters are defined in Figure 4. The ray encounters four interfaces with incidence angles θ1, θ2, θ3 and θ4 respectively. The refractive index of the external medium, the waveguide core and cladding are defined as n0, n1 and n2. For small incidence angle θ1 the ray will be transmitted through the tapered waveguide, but for large θ1, the ray will undergoes total internal reflection at the interface between the waveguide core and the cladding (if θ1 is big enough) or at the interface between the cladding and the external medium. In the later case, the ray will be first guided in the cladding, and after few reflections its incidence angle in the waveguide core will fulfill the total internal reflection requirement of the core. From Snell-Descartes law we can calculate the critical angle θ4c at the interface between the cladding and the external medium and evaluate the angle θ1c that will lead to that critical angle.

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