Animal II

Pulse-TDM encoding offered even more promise than phase-encoding as an expandable scheme to ultimately replace Switched-Source TDM in area measurements for DOT. In order to evaluate Pulse-TDM, Animal I was then upgraded to perform simultaneous measurements at three wavelengths, and was renamed “Animal II” to signify this change. It employed Pulse-TDM encoding at 685nm, 780nm and 830nm, with a ~1ms risetime (DC-350Hz bandwidth) and a temporal skew of less than 200us. It was specifically designed to search for intrinsic optical scattering events (“fast signals”) in the whisker barrel cortex of rats following whisker stimulation. The source optode consisted of three 220um fibers arranged in a triad and secured with cyanoacrylate adhesive, and the detector optode consisted of a single 400um silica fiber. Both were secured inside the bore of a polystyrene pipette to provide both strain-relief and a means of mechanical support during placement. Measurements were conducted over a long period of time and the instrument performed well, however no event-related intrinsic scattering changes were detected.

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