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Review Article

Exp Neurobiol 2013; 22(3): 158-166

Published online September 30, 2013

© The Korean Society for Brain and Neural Sciences

In-vivo Optical Measurement of Neural Activity in the Brain

Shin Ae Kim1 and Sang Beom Jun2,3*

1School of Chemical & Biomolecular Engineering, Georgia Institute of Technology, Atlanta, GA30332, United States, Departments of 2Electronics Engineering, 3Brain and Cognitive Sciences, Ewha Womans University, Seoul 120-750, Korea

Correspondence to: *To whom correspondence should be addressed.
TEL: 82-2-3277-3892, FAX: 82-2-3277-3494


The optical neural recording techniques are promising tools in recent years. Compared to the traditional electrophysiological recording, the optical means offer several advantages including no inclusion of electrical noise, simultaneous imaging of a large number of neurons, or selective recording from genetically-targeted neurons. Overall the optical neural recording technique comprises the intrinsic and the extrinsic optical recordings. The methods for intrinsic neural recording employ the change of optical properties in brains such as blood flow/oxygenation, cellular volume change, or refractive index change without addition of external indicators. Those properties can be detected using various optical techniques including laser Doppler flowmetry (LDF), near-infrared (NIR) spectrometer, functional optical coherence tomography (fOCT), and surface plasmon resonance (SPR). The extrinsic monitoring techniques use fluorescence signals reflecting neuronal activity via chemical or genetic modification of the neuronal cells. Two most popular activity-dependent fluorescent probes, calcium indicators and voltage-sensitive fluorescent proteins will be examined in this review. The principles, the instrumentations and in vivo applications of those optical signal measurements are described.

Keywords: optical neural recording, intrinsic optical recording, extrinsic optical recording, calcium indicators, voltage-sensitive, fluorescent protein (VSFP)