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UNIVERSITY OF BUCHAREST
FACULTY OF PHYSICS Guest
2024-11-23 18:12 |
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Conference: Bucharest University Faculty of Physics 2017 Meeting
Section: Biophysics; Medical Physics
Title:
Design, construction and testing of an 8-channel system for surface EEG recordings in small animals
Authors:
Bogdan AMUZESCU (1), George COCINĂ (1,2), Ştefan FLORICĂ (1,3), Vasile CÎRLIG (1), Alice DASCĂLU (1)
*
Affiliation:
1) Dept. Biophysics & Physiology, Faculty of Biology, University of Bucharest
2) Smart Systems Consulting SRL, Bucharest
3) Dept. Geology, Faculty of Biology & Geology, “Babeş-Bolyai” University, Cluj
E-mail
bogdan@biologie.kappa.ro
Keywords:
EEG, zero-drift operational amplifier, instrumentation amplifier, Chebyshev active filters, multielectrode array
Abstract:
Clinical electroencephalography (EEG), developed by Hans Berger during his landmark experiments in 1925-1929, is a tremendously successful and insightful method. However, in vivo brain neuroelectrophysiology experiments in small laboratory animals exploring neural networks behavior use almost exclusively arrays of electrodes implanted stereotaxically or at least penetrating the dura mater, i.e. invasive techniques. Therefore we aimed to develop a less invasive EEG system for surface recordings using 8 bipolar leads with tiny silver electrodes placed on the skull, directly connected to a headstage containing instrumentation amplifiers in a miniature surface-mounted device circuit. Each channel was built around a TLV4333 integrated circuit, a low-cost rail-to-rail CMOS quad op-amp with internal offset cancellation using a proprietary technology, featuring extremely reduced voltage offset and time and temperature drift. The headstage was connected via shielded wires to the main unit, containing for each channel an inverting amplifier stage and a 6th order Chebyshev active low-pass filter (0-35 Hz) built using a Sallen-Key voltage-controlled voltage source design. The output of the EEG system was sampled with an Axon Instruments AD/DA interface driven by the pClamp10 software. We thoroughly tested the transfer functions (gain and phase shift) of amplifiers and filters. Subsequently we performed real-life tests of the equipment on an adult male Wistar rat, and we succeeded to prove an almost one-order-of-magnitude reversible decrease in spectral power density in the alpha range (8-12 Hz) of the Fourier transform of the signal recorded in parieto-occipital leads during exposure to intense light.
References:
Amuzescu B., Cocina G., S. Florica (2016): Miniature electrode array and system for experimental surface EEG recordings, Rom. J. Biophys. 26(2):69-82
Acknowledgement:
This work was supported from grant PN2 80/2012 to Prof. Aurel Popa-Wagner.
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