Functional Neuro imaging in the Mouse Brain
Developments in neuro-imaging of the mouse brain signals new era for integrating cognitive neuroscience and animal models. Researchers at Washington University have combined resting-state functional connectivity mapping with optical intrinsic signal imaging (fcOIS) to produce an excellent study of parcellation of function within the mouse brain.
fMRI techniques have previously transformed our understanding of human cognitive neuroscience bt its limitations have prevented further advancements that require similar animal models. fcOIS is a simple and elegant solution for indirectly mapping neuronal activity in small animals. This technique measures small changes in the absorption (or reflection) of light that occurs within the brain when neurons are activated. They carried out the study using a simple camera-based system which uses the Andor EMCCD camera (iXon 897) available from Scientifica.
The team at Washington achieved sequential illumination of the desired brain region with an LED ring, emitting at four different wavelengths. The LED and camera were time-sychronized and controlled by custom-made software. The camera was able to acquire images at a rate considerably above the heart and respiration rate of the subject. They used a full frame rate of 30Hz; which translated to a rate of 120Hz for the four different sequential wavelengths.
The image light intensities from the four different wavelengths were interpreted using a tissue spectroscopy model and translated into time traces in oxy and deoxyhemoglobin (HbO2 and HbR). This method uses indirect neurovascular response to map patterns of spontaneous brain activity. The team were able to demonstrate functional connections within the mouse brain during resting state and used the pattern of connections to produce a parcellation map of different functioning areas.
fcOIS provides a "high resolution, low cost and easy to use" system that opens a wealth of possibilities for many laboratories to introduce functional neuro-imaging to their ongoing studies of human disease.
These results matched expectations from previous studies and confirmed the validity of fcOIS data for neuro-imaging in mice.
The paper in full is available at PLoS One here.
White B R et al, January 2010, Imaging of Functional Connectivity in the Mouse Brain. PLos One, Volume 6, Issue 1
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