12 research outputs found
Termikus effektusok vizsgálata akusztooptikai eszközökben = Investigation of thermal effects in acusto-optical devices
Kutatási projektünk során különböző típusú és rendeltetésű akusztooptikai eszközökben kialakuló termikus jelenségeket vizsgáltuk. Kidolgoztuk az akusztooptikai effektus termikus modelljét, amelyben az akusztikus nyaláb elnyelődése, valamint az ultrahangkeltő elektromos és akusztikus veszteségei következtében felszabaduló hőmennyiség-eloszlást, az ennek megfelelő hőmérséklet-eloszlást szimuláltuk. A modellt akusztooptikai hatásfok-mérésekkel, valamint működő cellán végzett termovíziós mérésekkel fejlesztettük és ellenőriztük. A számolt és mért hőmérséklet-eloszlás segítségével kiszámoltuk az akusztooptikai kristályok optikai és akusztooptikai paramétereinek termikus változását, és ezeket integráltuk a fény hangoszlopon bekövetkező diffrakcióját és terjedését leíró modellünkbe. Megállapítottuk, hogy az üzemi hőmérsékleten kialakuló termikus lencse jelentősen befolyásolhatja a fénynyaláb terjedési irányát és intenzitás-eloszlását. Eljárásokat dolgoztunk ki az ultrahangkeltő veszteségeink csökkentésére a technológia javításával. Optimalizáltuk az akusztooptikai eszközök dobozolását hőtechnikai szempontból, és a nagyobb akusztikus teljesítményen működő eszközöket kiegészítettük egy kétkörös aktív hőelvezető és hűtőelemmel. A bevezetett módszerekkel sikerült az eszközök hőmérsékletnövekedését nagyobb elektromos teljesítmény esetén is korlátozni, valamint a hőmérséklet-eloszlás frekvenciafüggését és gradiensét a kristályban csökkenteni. | We examined theoretically and practically thermal effects in different type acousto-optic devices designed for different purposes. We elaborated a numerical model of the thermal processes appearing in these devices. In this model we calculate the heat distribution arising from the absorption of acoustic waves and electric transducer losses and calculate the corresponding temperature distribution across the device. The development of the model has been supported by continuous measurement of the acousto-optic interaction efficiency and temperature distribution on the acousto-optic crystal surfaces. Starting from the measured and calculated temperature distribution in the crystal we simulated the thermal changes of its photoelastic and optical parameters. We included the results in our model, which simulates the propagation of the optical beams through the acousto-optic crystal, and found that the thermal lens effect considerably influences their propagation direction and transversal intensity distribution. Based on the thermal imaging measurements we improved our acousto-optic transducer technology to reduce its losses. We optimized the housing of the devices to effectively remove the heat from the crystal walls and elaborated an active cooling system capable to control device temperature during operation. These improvements helped to limit and stabilize temperature increase and temperature gradients even at higher input electric power levels
Fast three-dimensional two-photon scanning methods for studying neuronal physiology on cellular and network level = Háromdimenziós, gyors, kétfoton-pásztázó eljárások sejt- és hálózatszintű idegsejtvizsgálatokhoz
Absztrakt. Az Orvosi Hetilap 2015. december 27-én megjelent 52. számának fenti közleményében [Orv. Hetil., 2015, 156(52), 2120–2126, DOI: 10.1556/650.2015.30329] Mezey Dávid nevét nem pontosan adták meg. A levelező szerző kérte a név helyesbítését.
Abstract. Erratum to the article published on December 27th 2015 in Issue 52 of Orvosi Hetilap [Orv. Hetil., 2015, 156(52), 2120–2126, DOI: 10.1556/650.2015.30329]. The name of Dávid Mezey was not correctly typed. The corresponding author asked for the following correction to be published
Random access three-dimensional two-photon microscopy
We propose a two-photon microscope scheme capable of real-time, three-dimensional investigation of the
electric activity pattern of neural networks or signal summation rules of individual neurons in a
0.6 mm 0.6 mm 0.2 mm volume of the sample. The points of measurement are chosen according to
a conventional scanning two-photon image, and they are addressed by separately adjustable optical
fibers. This allows scanning at kilohertz repetition rates of as many as 100 data points. Submicrometer
spatial resolution is maintained during the measurement similarly to conventional two-photon
microscop
Fast 3D Imaging of Spine, Dendritic, and Neuronal Assemblies in Behaving Animals
SummaryUnderstanding neural computation requires methods such as 3D acousto-optical (AO) scanning that can simultaneously read out neural activity on both the somatic and dendritic scales. AO point scanning can increase measurement speed and signal-to-noise ratio (SNR) by several orders of magnitude, but high optical resolution requires long point-to-point switching time, which limits imaging capability. Here we present a novel technology, 3D DRIFT AO scanning, which can extend each scanning point to small 3D lines, surfaces, or volume elements for flexible and fast imaging of complex structures simultaneously in multiple locations. Our method was demonstrated by fast 3D recording of over 150 dendritic spines with 3D lines, over 100 somata with squares and cubes, or multiple spiny dendritic segments with surface and volume elements, including in behaving animals. Finally, a 4-fold improvement in total excitation efficiency resulted in about 500 × 500 × 650 μm scanning volume with genetically encoded calcium indicators (GECIs)
Dendritic Spikes Induce Ripples in Parvalbumin Interneurons during Hippocampal Sharp Waves
Sharp-wave ripples are transient oscillatory events in
the hippocampus that are associated with the reactivation
of neuronal ensembles within specific
circuits during memory formation. Fast-spiking, parvalbumin-expressing
interneurons (FS-PV INs) are
thought to provide fast integration in these oscillatory
circuits by suppressing regenerative activity in
their dendrites. Here, using fast 3D two-photon
imaging and a caged glutamate, we challenge this
classical view by demonstrating that FS-PV IN dendrites
can generate propagating Ca2+ spikes during
sharp-wave ripples. The spikes originate from dendritic
hot spots and are mediated dominantly by
L-type Ca2+ channels. Notably, Ca2+ spikes were
associated with intrinsically generated membrane
potential oscillations. These oscillations required
the activation of voltage-gated Na+ channels, had
the same frequency as the field potential oscillations
associated with sharp-wave ripples, and controlled
the phase of action potentials. Furthermore, our results
demonstrate that the smallest functional unit
that can generate ripple-frequency oscillations is a
segment of a dendrite
Fast two-photon in vivo imaging with three-dimensional random-access scanning in large tissue volumes
The understanding of brain computations requires methods
that read out neural activity on different spatial and temporal
scales. Following signal propagation and integration across
a neuron and recording the concerted activity of hundreds of
neurons pose distinct challenges, and the design of imaging
systems has been mostly focused on tackling one of the two
operations. We developed a high-resolution, acousto-optic
two-photon microscope with continuous three-dimensional
(3D) trajectory and random-access scanning modes that
reaches near-cubic-millimeter scan range and can be adapted
to imaging different spatial scales. We performed 3D calcium imaging of action potential backpropagation and dendritic spike forward propagation at sub-millisecond temporal
resolution in mouse brain slices. We also performed volumetric
random-access scanning calcium imaging of spontaneous and
visual stimulation–evoked activity in hundreds of neurons
of the mouse visual cortex in vivo. These experiments
demonstrate the subcellular and network-scale imaging
capabilities of our system