A spherical treadmill system to train head-fixed adult rats

• Published in: Journal of neuroscience methods Vol. 297; pp. 22 - 30
• Main Authors: Miguelez Fernández, Anabel M.M., Burman, Ariel, Martínez Cáceres, Alfredo I., Mininni, Camilo J., Zanutto, B. Silvano, Lew, Sergio E.
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 01.03.2018
• Subjects: Animals; Auditory discrimination; Auditory Perception; Discrimination (Psychology); Equipment and Supplies; Equipment Design; Food; Head; Head Movements; Head-fixation; Learning; Male; Models, Animal; Motor Activity; Polystyrenes; Rats; Software; Spherical treadmill; Stress, Psychological; Auditory discrimination; Head-fixation; Spherical treadmill
• ISSN: 0165-0270; 1872-678X
• DOI: 10.1016/j.jneumeth.2017.12.018

•We present a novel spherical treadmill suitable to train adult rats.•The sphere freely rotates supported by 3 bearings and its movement is video tracked.•Head-fixation is used to facilitate acute electrophysiology and imaging recordings.•We designed a training protocol that gradually introduces animals to head-fixation.•Adult Long Evans rats were successfully trained in an auditory discrimination task. While spherical treadmills are widely used in mouse models, there are only a few experimental setups suitable for adult rats, and none of them include head-fixation. We introduce a novel spherical treadmill apparatus for head-fixed rats that allows a wide repertory of natural responses. The rat is secured to a frame and placed on a freely rotating sphere. While being head-fixed, it can walk in any direction and perform different motor tasks. Instead of being air-lifted, which is acceptable for light animals, the treadmill is sustained by three spherical bearings ensuring a smooth rotation in any direction. Movement detection is accomplished using a video camera that registers a dot pattern plotted on the sphere. Long Evans rats were trained to perform an auditory discrimination task in a Go/No-Go (walking/not-walking) paradigm. Animals were able to successfully discriminate between a 1 kHz and a 8 kHz auditory stimulus and execute the correct response, reaching the learning criterion (80% of correct responses) in approximately 20 training sessions. Our system broadens the possibilities of head-fixation experiments in adult rats making them compatible with spatial navigation on a spherical treadmill.