Extended Data Fig. 4: Measurement of movement in vivo using photobleaching.
From: Brain clearance is reduced during sleep and anesthesia
a, Fluorescent intensity measured in the frontal cortex following injection of 4 kDa FITC-dextran into the CPu (at t = 0). After a delay, fluorescent intensity rises to a maximum and then slowly decays. b, As with the experiments in gels, the spread of light in the brain had to be established. This was done using brain slices (Methods) and this figure shows a typical image obtained from a brain slice, which provided a measure of the standard deviation of the hemispherical gaussian σ. c, A typical recording in vivo of the recovery of fluorescence after photobleaching. A value for D was derived from the theoretical fit (red dashed line) to Eq. 5, as described in Methods. d, Throughout the experiment, the EEG and EMG signals were recorded and the power in the delta band (1–4 Hz) and theta band (5–10 Hz) derived, so that the vigilance state (WAKE, NREM or REM) could be determined (Methods).
