Methods for Voltage-Sensitive Dye Imaging of Rat Cortical Activity With High Signal-to-Noise Ratio

Department of Physiology and Biophysics, Georgetown University Medical Center, Washington, DC Submitted 1 November 2006; accepted in final form 8 May 2007 We describe methods to achieve high sensitivity in voltage-sensitive dye (VSD) imaging from rat barrel and visual cortices in vivo with the use of a blue dye RH1691 and a high dynamic range imaging device (photodiode array). With an improved staining protocol and an off-line procedure to remove pulsation artifact, the sensitivity of VSD recording is comparable with that of local field potential recording from the same location. With this sensitivity, one can record from 500 individual detectors, each covering an area of cortical tissue 160 µm in diameter (total imaging field 4 mm in diameter) and a temporal resolution of 1,600 frames/s, without multiple-trial averaging. We can record 80–100 trials of intermittent 10-s trials from each imaging field before the VSD signal reduces to one half of its initial amplitude because of bleaching and wash-out. Taken together, the methods described in this report provide a useful tool for visualizing evoked and spontaneous waves from rodent cortex. Address for reprint requests and other correspondence: J.-Y. Wu, The Research Building, WP26, 3970 Reservoir Rd., NW, Washington, DC 20057 (E-mail: wuj{at}georgetown.edu )