9 research outputs found
Bidirectional optogenetic control of inhibitory neurons in freely-moving mice
Objective: Optogenetic manipulations of excitable cells enable activating or
silencing specific types of neurons. By expressing two types of exogenous
proteins, a single neuron can be depolarized using light of one wavelength and
hyperpolarized with another. However, routing two distinct wavelengths into the
same brain locality typically requires bulky optics that cannot be implanted on
the head of a freely-moving animal.
Methods: We developed a lens-free approach for constructing dual-color
head-mounted, fiber-based optical units: any two wavelengths can be combined.
Results: Here, each unit was comprised of one 450 nm and one 638 nm laser
diode, yielding light power of 0.4 mW and 8 mW at the end of a 50 micrometer
multimode fiber. To create a multi-color/multi-site optoelectronic device, a
four-shank silicon probe mounted on a microdrive was equipped with two
dual-color and two single-color units, for a total weight under 3 g. Devices
were implanted in mice expressing the blue-light sensitive cation channel ChR2
and the red-light sensitive chloride pump Jaws in parvalbumin-immunoreactive
(PV) inhibitory neurons. The combination of dual-color units with recording
electrodes was free from electromagnetic interference, and device heating was
under 7{\deg}C even after prolonged operation.
Conclusion: Using these devices, the same cortical PV cell could be activated
and silenced. This was achieved for multiple cells both in neocortex and
hippocampus of freely-moving mice.
Significance: This technology can be used for controlling spatially
intermingled neurons that have distinct genetic profiles, and for controlling
spike timing of cortical neurons during cognitive tasks.Comment: 11 pages, 9 figure
Recommended from our members
New Phases and Dissociation-Recombination of Hydrogen Deuteride to 3.4Â Mbar
We present infrared absorption studies of solid hydrogen deuteride to pressures as high as 340 GPa (100 GPa ¼ 1 Mbar) in a diamond anvil cell and temperatures in the range 5–295 K. Above 198 GPa the HD sample transforms to a mixture of HD, H2, and D2, interpreted as a process of dissociation and recombination. Three new phase lines are observed, two of which differ remarkably from those of the high pressure homonuclear species, but none are metallic. The time-dependent spectral changes are analyzed to determine the molecular concentrations as a function of time; the nucleon exchange achieves steady state concentrations in ∼20 h at ∼200 GPa.Physic
Covalency is Frustrating: La2Sn2O7 and the Nature of Bonding in Pyrochlores under High Pressure-Temperature Conditions.
Natural specimens of the pyrochlore (A2B2O7) compounds have been found to retain foreign actinide impurities within their parent framework, undergoing metamictization to a fully amorphous state. The response to radionuclide decay identifies pyrochlore systems with having high radiation tolerance and tailored use in radioactive waste applications and radionuclide sequestration. High pressure is a powerful pathway to high density states and amorphization with parallels to radiation-induced processes. Here, La2Sn2O7 is evaluated under extreme conditions via the combination of laser heating in a diamond anvil cell with X-ray diffraction and Raman spectroscopy. The measurements are supported by ab initio random structure searching and molecular dynamics calculations. A new ground state at 70 GPa is revealed, and high temperature annealing is fundamental to access its crystalline ground state and fully determine the structure. This crystalline phase ( P21/ c) retains its structural integrity during decompression and is fully recoverable to ambient conditions. The final state of the system is shown to be highly pathway dependent due to the covalent nature of the Sn-O bonding. The Tc pyrochlore, La2Tc2O7, is analyzed for similarities in the bonding to determine the likelihood of an analogous pathway dependency to a final state.Royal Societ
Covalency is Frustrating: La<sub>2</sub>Sn<sub>2</sub>O<sub>7</sub> and the Nature of Bonding in Pyrochlores under High Pressure–Temperature Conditions
Natural specimens
of the pyrochlore (A<sub>2</sub>B<sub>2</sub>O<sub>7</sub>) compounds
have been found to retain foreign actinide impurities within their
parent framework, undergoing metamictization to a fully amorphous
state. The response to radionuclide decay identifies pyrochlore systems
with having high radiation tolerance and tailored use in radioactive
waste applications and radionuclide sequestration. High pressure is
a powerful pathway to high density states and amorphization with parallels
to radiation-induced processes. Here, La<sub>2</sub>Sn<sub>2</sub>O<sub>7</sub> is evaluated under extreme conditions via the combination
of laser heating in a diamond anvil cell with X-ray diffraction and
Raman spectroscopy. The measurements are supported by ab initio random
structure searching and molecular dynamics calculations. A new ground
state at 70 GPa is revealed, and high temperature annealing is fundamental
to access its crystalline ground state and fully determine the structure.
This crystalline phase (<i>P</i>2<sub>1</sub>/<i>c</i>) retains its structural integrity during decompression and is fully
recoverable to ambient conditions. The final state of the system is
shown to be highly pathway dependent due to the covalent nature of
the Sn–O bonding. The Tc pyrochlore, La<sub>2</sub>Tc<sub>2</sub>O<sub>7</sub>, is analyzed for similarities in the bonding to determine
the likelihood of an analogous pathway dependency to a final state