Robust, hands-free freely moving imaging

Two crucial things one has to take of when it comes to doing fUS in freely moving animals performing behavior: first is that the behavior timescale matches the timescale of the brain hemodynamic response (on the order of seconds) and second is that the animal movement and the behavior are not impaired by the tethered fUS probe.

As an example behavior optimized for fUS measurement, we can consider an extended version of evidence accumulation based decision making in rats. Rather than the milisecond time-scale, the behavior is elongated such that the evidence (in this case a sequence of randomized clicks) is presented over multiple secons. The rat can self-initiate each trial, wait for the clicks to commence and play, and then decide which side had more clicks play on. The rat can then move to the correct nose port for a reward. For complete behavioral training protocol, please refer to El Hady et al. 2023.

To ensure that the behavior of the animal is unimpaired and can move freely we designed the following tethering system, where a system of weights and ballances keeps the chord elevated and unobtrusive to the rat’s movements: