Pal Maak

• Budapest University of Technology and Economics

Neural circuits support rapid visual learning. However, due to technical roadblocks, it is not known how visual circuits represent multiple features or how behaviorally relevant representations are selected for long-term memory. Here we developed Moculus, a head-mounted virtual reality platform for mice that covers the entire visual field, and allo...

This paper analyzes design considerations to realize acousto-optic deflectors in TeO 2 single crystal to be used with ultrashort pulses, especially in multi-photon microscopy. These deflectors are primarily designed for 2D and 3D scanners, therefore it is an important aspect to optimize the combination of different deflection directions within a sc...

Simultaneously with fast 3D imaging, we generated holograms from multiple spots by introducing sine waves with non-linear frequency chirps into the acousto-optical deflectors and activated over 40cells with high resolution within 16ms in large volumes.

Related to Figure 1. z stack from 650 to 100 μm under the pia mater in the visual cortex of a Thy1-Cre mouse was taken using the 3D DRIFT AO microscope. For cre-dependent expression of the GCaMP6f Ca2+ sensor, we used an AAV vector injected into the V1 region. Raw fluorescence data were normalized for radially inhomogeneous illumination as previous...

Related to Figures 2 and 3. Twelve spiny dendritic segments of a GCaMP6-labeled layer II/III pyramidal cell located in V1 were simultaneously imaged using 3D ribbon scanning. Note the large and spatially inhomogeneous movement artifacts during recording of activity in an awake animal.

Movie S7. Multi-3D Ribbon Scanning Movie Before and After the Correction of Motion Artifacts Related to Figure 3. The first block is the same movie as Movie S5. In the second block of the movie, motion artifacts were eliminated by shifting back each frame of all regions by the local projection of the net displacement vector of the brain (see text...

Movie S8. Representative Example of Cell Selection and Image Acquisition during Chessboard Scanning in 3D Related to Figures 2, 3, and 4. Populations of V1 neurons were labeled with GCaMP6f protein expressed by non-specific promoter. First, a z stack was obtained using the 3D AO microscope. Second, ROIs, here small squares centered on neuronal som...

Movie S9. Three-Dimensional Recording Neuronal Networks in V1 with Chessboard Scanning during Visual Stimulation Related to Figure 4. The same populations of V1 neurons as in Movie S8. Activity was recorded in awake, head-restrained animals during visual stimulation. The upper left corner shows the video of raw fluorescence data arranged in chessb...

Movie S11. Snake Scanning of a Spiny Dendritic Segment in the Moving Brain of a Behaving Mouse Related to Figure 6. V1 neurons were sparsely labeled using the GCaMP6f sensor. A spiny dendritic segment was selected for volume imaging using snake scanning at 10 Hz. Motion artifacts were removed and data are shown as relative fluorescence changes (ΔF...

Related to Experimental Procedures. Signal generation and high-speed communication with the DAC chip performed by the FPGA (see also Figure S3).

Related to Experimental Procedures. This MATLAB function returns the four center frequencies in MHz, the four frequency step speeds in MHz/s, and the four frequency derivate step values in MHz/s2 for any desired point in the field of view with any desired speed vector.

Document S1. Supplemental Experimental Procedures, Figures S1–S10, and Tables S1 and S2

Movie S5. 3D Ribbon Scanning of a Spiny Dendritic Segment during Visual Stimulation Related to Figure 1. Similar example as Movie S4. A GCaMP6-labeled spiny dendritic segment from a different layer II/III neuron was imaged using 3D ribbon scanning.

Related to Experimental Procedures. This MATLAB function returns the register values transferred to the FPGA for synthesis. Center frequencies, frequency steps, and frequency derivate steps calculated for each scanning segment are the inputs, while register values FR, FSR, and FDSR are the output.

Related to Figure 1. A 140 μm GCaMP6-labeled spiny dendritic segment situated in a 60 μm range of z-scanning was imaged using 3D ribbon scanning.

Related to Figure 6. V1 neurons were sparsely labeled using the GCaMP6f sensor. Ten labeled neurons were centered in cubes. Volume imaging was performed simultaneously in the ten cubes with 10 Hz temporal resolution. Finally, motion artifacts were removed and data are shown as relative fluorescence changes (ΔF/F). Note the fine Ca2+ dynamic in the...

Related to Experimental Procedures. z stack from 0 to 820 μm under the pia mater in the visual cortex of a Thy1-Cre mouse was taken using 2D galvo scanning. Detectors were fixed to the objective arm (traveling detector system) to minimize the detection pathway and maximize detection of backscattered fluorescent light. For cre-dependent expression o...

Movie S1. Validation of 3D DRIFT AO Scanning by Bleaching a Polyhedron Shape in a Homogeneous Fluorescent Sample Related to Figure 1. Resolution and point stability of the 3D DRIFT AO scanning method was validated by “burning” a polyhedron shape in a homogeneous fluorescent sample using photo bleaching. Each edge of the polyhedron was scanned by a...

Movie S3. Method of Selection of 3D Ribbons for Fast Scanning of Spiny Dendritic Segments Related to Figure 1. The video demonstrates how guiding points are selected, how the 3D trajectory is fitted according to the guiding points, and, finally, how the plan of the ribbon is generated for 3D ribbon scanning. See also the “Selection of the 3D traje...

Movie S10. Multi-Layer, Multi-Frame Imaging of Neuropil Activity with Over 100 Hz Temporal Resolution Related to Figure 5. V1 neurons were sparsely labeled using the GCaMP6f sensor and measured simultaneously in four different z planes (z1 = −380 μm, z2 = −350 μm, z3 = −295 μm, z4 = −130 μm) with 101 Hz temporal resolution during visual stimulatio...

Understanding 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-poin...

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.

Introduction: Two-photon microscopy is the ideal tool to study how signals are processed in the functional brain tissue. However, early raster scanning strategies were inadequate to record fast 3D events like action potentials. Aim: The aim of the authors was to record various neuronal activity patterns with high signal-to-noise ratio in an optical...

Our aim is to establish a novel combined acousto-optical method for in vivo imaging of the human retina with the two-photon microscope. In this paper we present modeling results based on eye model samples constructed with parameters measured on patients. We used effectively the potential of the electronic compensation offered by the acousto-optic l...

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 activ...

The acousto-optical crystals are frequently used, indispensable elements of high technology and modern science, and yet their precise numerical description has not been available. In this paper an accurate, rapid and quite general model of the AO interaction in a Bragg-cell is presented. The suitability of the simulation is intended to be verified...

In this paper a novel method of computing the optical rotation of a parallel plated crystal is presented. The calculation is based on Fourier optics and solves generally the vectorial Maxwell's equations for both the refraction and propagation. It does not require the paraxial approximation, instead, the incident beam may have complex shape, not on...

A novel modeling technique is introduced for modeling light propagation in slightly inhomogeneous, anisotropic and optically active materials. With the aid of the model the phenomenon of acousto-optic interaction can be efficiently and accurately simulated in a completely general approach. The applied inhomogeneity caused by the sound waves can be...

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...

We report here new acousto-optic designs dedicated for applications in the edge of today's research: generation and spatially scanning of highly stable femtosecond laser pulse trains possibly with variable repetition rate, to provide optimal circumstances for a variety of applications: pump-probe experiments, laser spectroscopy, laser microscopy. T...

In the present paper we analyze the electric and acoustic losses in acousto-optic devices, especially in their ultrasonic transducers and the related thermal effects. We include electric and acoustic losses into the classical electric equivalent model of the transducer, to explain the characteristics of the measured electric and thermal behavior. M...

We present a comprehensive study of the acoustic-to-optic phase transfer during anisotropic Bragg diffraction. Our results refine the operating theory of widely used acousto-optic implementations such as pulse shapers, delay lines, and phase modulators.

There is a high demand for a computational model that calculates effectively the phase and amplitude distribution of the beams emerging from an acousto-optic cell. We present a model based on a new algorithm that is capable to solve the vectorial optical wave equation on consecutive planes in an optically anisotropic medium with an arbitrary refrac...

The optical phase of a beam diffracted in an acousto-optic interaction may be directly controlled with the acoustic phase, but limitations occur in the case of commonly used AO devices, based on strong anisotropic AO interaction. In our study we present measurement and theoretical calculation of the phase shift of a laser beam diffracted in an AO d...

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 m m × 0.6 m m × 0.2 m m volume of the sample. The points of measurement are chosen according to a conventional scanning two-photon image, and the...

Numerical simulation of diffraction on thick holographic gratings in shift-multiplexed optical data storage application is presented. The grating is generated by the interference of a spherical reference wave and a plane signal wave corresponding to a single pixel of the input data page. To describe diffraction on this weak-index-modulated grating,...

The effect of heat in acousto-optic devices is a persistent problem with respect to the electric, acoustic and optical behavior of the device. The temperature differences across the acousto-optic crystal driven at acoustic power levels up to 1W, common for operation of these devices, can reach values of 90–100°C that cause significant refractive in...

We propose a two-photon microscope scheme capable of real time, 3D investigation of the neural activity in a 0.6 x 0.6 x 0.2 mm3 volume with sub-micrometer spatial resolution.

We propose a nonlinear microscope scheme being capable of simultaneous, 3D investigation of the electric activity pattern of neural networks or signal summation rules of individual neurons in a 0.6×0.6×0.2 mm³ volume with sub-micrometer spatial resolution.

In the present paper, we discuss the effect of an easily implemented type of transducer electrode segmentation on the electrical and optical performance of bulk acousto-optic filters. Segmentation consisting in transducer upper electrode shaping allows realization of filters with very large interaction length with transducer electric impedances not...

Optically realized continuously variable true-time delay of microwave pulses is demonstrated in a heterodyne system involving an acousto-optic deflector and a specially designed electro-optic modulator. The system realizes the time delay by frequency dependent phase shifting of the spectral components of the signal (FDPC technique). A new feature o...

Optical heterodyne acousto-optic delay line applying frequency dependent phase shift provided by liquid crystal spatial light modulator is presented. We experimentally demonstrate continuously variable true time delay of 1 μs long microwave pulses between ±300 ns.

We present an optical heterodyne acousto-optic delay line performing true-time delay of microwave pulses based on the direct practical realization of the time shifting possibility embedded in the Fourier transformation of the differentially phase shifted spectrum. New feature of the system is the demonstration of continuously variable time delay by...

A true-time optical delay line for short radiofrequency (RF) pulses using path length dispersion is proposed. It is an optical implementation of the linear phase-shift theorem of the Fourier transformation. Acoustooptic signal processing is used for conversion into the optical frequency domain and for spatial Fourier decomposition of the pulse. The...

A flash-lamp-pumped Er:Cr:YSGG laser at 2.79-µm wavelength has been acousto-optically Q switched. The Q-switched pulse energy and duration depend on pump pulse level and relative Q-switching time. Limits of single-pulse operation with the given acousto-optic diffraction efficiency have been determined. Resonator length, position of the Q switch, an...

A two-dimensional acousto-optic deflector has been combined with a large angular acceptance, laser diode-pumped Nd:YAG optical amplifier in order to obtain a scanning system with high angular resolution and with high and uniform optical transmission. Experiments have been carried out in order to optimize the set-up for intensity distribution and op...

A true time optical delay line for short pulses by means of acousto-optic signal processing is presented. A theoretical description of the heterodyning delay line based on spatial Fourier decomposition and differential optical phase shift of the pulse frequency components is given. 2 μs time delay of 0.5 μs long pulses with maximum optical phase sh...

The purpose of this work is to find a reliable approach for one- and two-dimensional acousto-optic deflector design. The design method is based on an improved theoretical model of anisotropic acousto-optic interaction. The new feature of this model is the application of new approximations together with the inclusion of effects that were previously...

A novel approach for one and two dimensional acoustooptic deflector design is presented. Two dimensional deflectors are optimally built of two adjacent Bragg cells in acoustically rotated configuration. The depleting effect of second order diffraction is compensated by a small change of the optical incidence angle. High bandwidth devices working be...

Correspondence should be addressed to B. Rózsa, rozsa.balazs@koki.mta.hu Keywords: two-photon, 3D, in vivo, random-access scanning 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 a...

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 e...