Functional MRI in Awake Unrestrained Dogs
(A) Callie in the training apparatus, which consisted of a replica of the head coil inside a tube of the approximate diameter of the MRI bore. Consistent positioning of the head was achieved by training the dog to place her head in a chin rest molded to the lower jaw from mid-snout to behind the mandible. The chin rest was affixed to a wood shelf that spanned the head coil but allowed enough space for the paws underneath. No restraints were used. The training procedure gradually shaped the desired behavior of placing the head in the rest and not moving through positive reinforcement only. Dogs were free to exit the apparatus at any time. (B) McKenzie inside the real head coil in the MRI. Her handler is giving a hand signal that denotes upcoming “reward.” We used a simple instrumental conditioning task in which the required behavior was to place the head on the chin rest and not move. After a variable interval of approximately 5 s, a hand signal was given that indicated whether a reward would be delivered. The dog had to continue holding still during this period to get the reward. The left hand up indicated a hot dog reward, while both hands pointing toward each other horizontally indicated no-reward. The hand signals were maintained for approximately 10 s. Reward-trials ended by the handler reaching in with the food to the dog. Person in the photograph has given written informed consent for publication.