Fig. 6.

Two-photon imaging (λ₀ = 800 nm) of vasomotion in cortical arterioles across both hemispheres of an awake, head-fixed mouse through dual transcranial windows. Blood plasma is stained with fluorescein dextran. (a) Maximally projected image stack across 500 µm of the preparation. The arbitrary-line-scan path (yellow) spans both hemispheres and operated at 71 Hz. The dark region in the middle corresponds to a physical mask placed over the remaining cranial bone above the midline. The expanded images are single planes in each hemisphere and serve to highlight the path of the line-scan through individual vessels whose diameters were concurrently monitored. (b) Vasomotor oscillations measured simultaneously from pial arteries in the right (green) and left (red) hemispheres. An expanded and overlaid view of the highlighted time band (gray) is shown on the right. (c) Spectral power of variation in diameter from the two arterioles and a venule (panel a) indicate vasomotion in the arterioles but not in the venule. Spectra were calculated from 540 s traces and a bandwidth (FWHM) of 0.03 Hz. The system noise (gray) was found by measuring the diameter of 8 to 20 µm fibers imbedded in clear cement and measured 3 to 4 mm off axis. The data represents an average over 24 measurements. (d) Cross-correlation of the diameter for the arterioles from panel b reveals strong synchrony of the arterial diameter oscillations across hemispheres. The time-lag at the peak is 0.0 ± 0.1 s. (e) The black curve is the magnitude of the spectral coherence between the two arterioles as calculated with a bandwidth of 0.04 Hz. The gray curve is the coherence for two fibers across an equivalent sized field.