Monthly Archives: January 2013

A multimodal microimplant for combined light/liquid delivery and multi-site electrical recording

As optogenetic neuronal control strategies develop and get widely adopted in neurobiology labs, the demand for devices allowing combined light delivery and electrophysiological recording is growing. These devices, commonly called opto-electrodes or optrodes, already exist under a wide variety of forms, from the simple home made single optical fiber + single electrode to more complex microfabricated multi-fiber/multi-electrode systems. In the past years, Zhang et al. integrated an optical fibre in a Utah Array, and NeuroNexus assembled an optical fiber on their standard silicon shaft. Other groups implemented waveguides directly into the optrode fabrication process: Cho et al. integrated a microstructured SU-8 waveguide on the shaft of a Michigan Probe and the group of Ed Boyden integrated 12 silicon oxynitride waveguides on silicon shafts (paper1, paper2). Royer et al. in the Buszaki lab managed to establish silicon based shaft arrays with integrated optical fibers.

In a recent paper published in “Lab on a Chip”, the Stieglitz and Lüthi labs introduced a novel optrode which also comprises a microfluidic channel for liquid delivery at the tip of the probe. This channel can be used for example to inject a solution containing a virus right under the waveguide tip and around the electrical … Continue reading

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A photoconvertible genetically-encoded calcium indicator

One of the primary goal of neuroscience research is to dissect the role of different cell-types in neuronal circuits. Thanks to the development of optogenetic reporters and control tools in recent years, researchers can now optically control and monitor the activity of genetically defined neuronal populations. Going deeper into the understanding of neuronal circuit requires to follow and control the activity of individual cells within these genetically-defined populations. Imaging the activity of individual neurons in vitro and in vivo can be achieved with classical microscopy techniques but labelling and following the activity of arbitrarily defined subsets of cells in a given population remains hard to implement. Optical highlighters which can be photoactivated or photoconverted are routinely used to label cell subpopulations but have only been used so far for anatomical tracing or cell migration studies. In a recent study published in JACS, Campbell and coworkers introduce a photoconvertible genetically-encoded calcium indicator, providing the possibility to easily monitor the activity of subsets of cells of a given cell type.

This dual-function Ca2+ indicator was made by combining two of the most powerful implementations of fluorescent protein (FP) technology: the “highlighters” that can be converted from non-fluorescent to fluorescent or from one … Continue reading

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