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MB-SWIFT fMRI studies in head-fixed behaving rats

Jaakko Paasonen¹, Petteri Stenroos^1,2, Hanne Laakso¹, Tiina Pirttimäki¹, Ekaterina Zhurakovskaya¹, Raimo A Salo¹, Heikki Tanila¹, Djaudat Idiyatullin³, Michael Garwood³, Shalom Michaeli³, Silvia Mangia³, and Olli Gröhn¹
¹A.I.V. Institute for Molecular Sciences, University of Eastern Finland, Kuopio, Finland, ²Grenoble Institut des Neurosciences, Grenoble, France, ³Center for Magnetic Resonance Research, University of Minnesota, Minneapolis, MN, United States

Here we introduce a novel approach for fMRI studies in head-fixed and minimally restrained rats that can express behavior. Our approach links global network activity to behavior and has potential to enable novel experimental designs in neuroscience studies.

Figure 1. The implant for head-fixation (A) with EEG electrode connector (B), a head-fixed rat wearing walking harness in a custom-made habituation and imaging holder for behavioral studies (C), and a habituated rat inside the 9.4T MRI scanner. Two 2 mm pins penetrating the implant (A, B) allow a robust head-fixation (C). Warm-water circulation kept the platform of the holder warm (C). The nose cone was remotely removed (compare C and D) and returned when necessary. A single loop transmitter-receiver coil was placed around the implant and below the head-fixing pins (D) to conduct MRI.

Figure 4. Activation maps (A-E) obtained during spontaneous behavior. Timings of the behavior are shown on the fMRI time series as shaded regions. The block design analysis included only a single event. In A, the rat was whisking. In B, the rat was sniffing. In C, the rat expressed increased arousal. In D, the rat tried to walk. In E, the rat tried to walk but paws slipped. The maps are overlaid on anatomical images. The slight mismatch between images and maps originates from the susceptibility-induced signal void in anatomical images that is not present in the MB-SWIFT images.