Ethical approval for these methods was obtained from the Auburn University Institutional Animal Care and Use Committee and all methods were performed in accordance with their guidelines and regulations. For auditory exposure, progression through the sessions is based on week number. For stationing sessions, a specific session-specified performance criterion (e.g., at least eleven-second duration of chin targeting), must be met before the trainer may advance the dog to the next session in that training phase. Otherwise, that step is repeated.

1. Auditory Exposure sessions

NOTE: These sessions constitute passive exposure and active classical counterconditioning of a positive Conditioned Emotional Response (CER) to MRI scanner noise; the scanner noise is established as a stimulus predicting the access to toy play or food rewards. Exposure sessions occur once per week for approximately 10 min.

1. Passive Exposure (PE) sessions are ambient, 40-70 decibel (dB) exposure to MRI scanner noises. Transport the dog to a familiar exercise area and allow the dog to walk around while audio playback is quietly audible at the session-specified volume through a portable Bluetooth speaker (see Table of Materials). Conduct three PE sessions of 10 min playback of scanner noise, once per week for three weeks (PE₁ 40-60 dB, PE₂ 65 dB, PE₃ 70 dB).
2. Active Exposure (AE) sessions utilize a standard classical conditioning paradigm and are conducted after the three PE sessions. Transport the dog to a familiar indoor training room and run through ten trials of the short-delay classical conditioning procedure (see Figure 2).
   1. Play scan audio at the session-specified volume for 10 s.
   2. After 10 s have elapsed, engage in 20 s of toy-play (or continuous food reward) with the dog while the scanner noise is still audible.
   3. After 20 s of play, retrieve the toy from the dog and pause the noise. Wait with the dog (in silence, dog without toy/food) for 10 s.
   4. After this delay, start the next trial. Conduct ten trials per session.
   5. Volume is incrementally increased over sessions. Conduct an AE session once per week for twelve weeks (AE₁ 45 dB, AE₂ 50 dB, AE₃ 55 dB, AE₄ 60 dB, AE₅ 65 dB, AE₆ 70 dB, AE₇ 75 dB, AE₈ 80 dB, AE₉ 85 dB, AE₁₀ 90 dB, AE₁₁ 100 dB, AE₁₂ > 100 dB).

Figure 2: Active Exposure. Active Exposure (AE) is a short-delay classical conditioning procedure. 10 s CS (i.e., scan audio presented by itself), 20 s CS + US (i.e., ball and scan audio presented together), 10 s delay (no ball, no scan audio). After this delay, the trial starts over. There are ten trials per session, with incremental volume increases over sessions. Please click here to view a larger version of this figure.

NOTE: Collect the following audio: MRI scanner baseline, shim, localizer (scout), MPRAGE, GRE Field, EPI, Multiband EPI, DTI, and RESOLVE DTI, using, for example, a smartphone's audio recording app through the open door of a 3T MRI suite during phantom scans. Determine volume level of audio playback during training sessions via a decibel meter phone app.

2. Stationing sessions

NOTE: These sessions are divided into two phases: Open environment and Mock MRI. After the chin-to-object target is learned, durations are increased on a percentile schedule of 10% increases. As new elements and pieces of equipment are added into the training context, certain criteria of the behavior (e.g., duration) are temporarily relaxed:
1) In the stationing sessions, the trainer trains a nose-touch behavior to a folded towel and then a chin rest on a folded towel. That chin rest behavior is generalized to occur in a foam chin rest and gradually built to a 5 min bout duration.
2) Simultaneously, robust down and stay behaviors are built and maintained.
3) Those behaviors are then conditioned to occur in an enclosed space (i.e., tunnel) and at a 3' elevation.
4) The dog is then acclimated to the head enclosure (mock human extremity RF coil).
5) Ear padding is introduced, and scan audio is (re)introduced in the context of the stationing behavior.
The dog will ultimately be able to perform a robust chin rest with head and body enclosed at a 3' elevation, with ear padding and scan audio playing at 90 + decibels (dB), for at least 5 min bouts. On reinforcement – some dogs are inherently more motivated by food, whereas others are more motivated by play or praise⁹. In "click-then-treat" (C/T), the T does not necessarily mean food treats, rather it refers to the reward procedure, whatever that may be for that particular dog at that particular stage in its training. Although food rewards lend themselves to higher rates and stiller repetitions of behavior, whatever the dog prefers can be used initially, even if it is high-motion play (e.g., ball, tug). As the chin target behavior becomes more resilient against distraction and duration, transition to using food rewards. Eventually, toy play can be saved for long-duration or chained bouts of chin rest performance.

1. Phase 1 – Open environment
   1. Charge the clicker. Build an association between the 'tic-toc' of the clicker and the dog's primary reward (e.g., food) while capturing attention. Conduct rapid repetitions of C/T events for attention (body orientation towards and/or eye contact); toss the treats to reset the dog's position. Conduct this session once.
      NOTE: This session usually takes no more than 3 min. It can be longer or repeated if the trainer is not seeing signs that the clicker is being established as a conditioned reinforcer-orientation towards the trainer and emission of reward-seeking behaviors upon hearing the click are good indications that the clicker is becoming a meaningful signal to the dog.
   2. Capture chin target to towel. With the dog standing, sitting, or in a down, C/T for looking at, then investigating (i.e., sniffing) the towel. Once that is occurring reliably, C/T for any nose-to-towel, and then chin-to-towel contact. Build towel contact duration to 2 s.
      1. Repeat this session until the dog will chin target for 2 s; each session should last approximately 5 min.
         NOTE: If a dog is struggling with this step, the trainer may (a) rub a treat on the towel to get the behavior started via a food odor lure and/or (b) teach the dog a nose target (nose-to-palm), then a chin target (chin-to-palm), and then cue for a chin target over the towel.
   3. Chin-to-towel target with short duration and addition of cue. With the dog standing, sitting, or in a down, C/T for 1-2 s of chin contact to the towel. Say "rest" while the dog is touching or about to touch the towel. After many repetitions of 1-2 s bouts, C/T after 3, then 4, then 5, then 7 s.
      1. Repeat this session until the dog will chin target for 7 s; each session should last approximately 5 min.
         NOTE: Vary the bout lengths of each chin rest so that the next repetition is not always longer than the previous repetition (i.e., 1", 1", 3", 1", 5", 2", 6", 4", 1", 2", 7", instead of, 1", 1", 1", 1", 2", 2", 3", 4", 5", 6", 7").
   4. Chin rest on towel in a down and addition of distraction. With the dog in a down, cue "rest" and C/T for 1-5 s of chin-to-towel contact. Gradually add visual and acoustic distractions in the form of the trainer moving her hands and feet (e.g., knock on ground, wiggle fingers, shuffle foot, etc.). Build chin-to-towel contact duration to 11 s. Increments can be 1"-5", 6"-7", 8", 9-10", 11"+.
      1. Repeat this session until the dog will chin target for 11 s; each session should last approximately 5 min.
   5. Chin rest on towel with distance. With the dog in a down beside a folded towel or stack of folded towels, cue "rest" and C/T for 1-3 s of chin-to-towel contact. Cue the behavior from progressively farther away (i.e., sitting on ground, kneeling, standing). Build chin-to-towel contact duration to 16 s. Increments can be 1"-3", 4"-8", 9"-11", 12"-14", and then 16"+.
      1. Repeat this session until the dog will chin target for at least 16 s; each session should last between 5 and 10 min.
   6. Chin rest on towel with increasing duration and distance. With the dog in a down beside a folded towel or stack of folded towels, cue "rest" and C/T for 1-11 s of chin contact. Build chin-to-towel contact duration to 26 s. Increments can be 1"-11", 12"-16", 17"-19", 21"-23", 26"+.
      1. Repeat this session until the dog will chin target for at least 26 s; each session should last between 5 and 10 min.
   7. Introduce foam chin rest. C/T for any investigation (i.e., sniffing, close proximity, orientation towards) of the foam chin rest apparatus. After several reinforced investigations of the apparatus, cue "rest" and C/T for 1-10 s of chin contact. Build duration to 40 s. Increments can be chin rest for 1"-10", 11"-21", 23"-31", 40"+.
      1. Repeat this session until the dog will chin target for at least 40 s; each session should last between 5 and 15 min.
         NOTE: Construct the rolled foam chin rest apparatus to fit each individual dog's muzzle; for a Labrador-sized dog, make a foam chin rest measuring 6" wide with a 4" wide by 2.5" deep notch cut out of the middle. This material is safe to take into the MRI environment.
   8. Chin rest in foam chin rest with increasing distraction and duration. With the dog in a down beside the foam chin rest, cue "rest" and C/T for 1"-23" of chin contact. Gradually add visual and acoustic distractions. Build duration to 73 s, with and without distraction. Increments can be 1"-23", 26"-31", 34"-45", 50"-60", and 73"+.
      1. Repeat this session until the dog will chin target for at least 73 s; each session should last between 5 and 15 min.
2. Phase 2 – Mock MRI.
   NOTE: To assemble the stationary Mock MRI, compile a tunnel (proxy MRI bore, 70 cm diameter cardboard concrete form tube cut to a length of six feet and elevated on a three-foot high folding table), a plywood platform, an acrylic mock radio frequency (RF) receiver coil, the foam chin rest apparatus, and a speaker system (see Table of Materials). Stabilize the mock bore on the table with two plywood braces. Affix buffer pads affixed to the interior of the mock RF coil to provide padding against the dogs' ears and additional cranial stabilization/placement feedback.
   1. Introduce bore and elevation with reduced duration. Conduct the entire first session with the mock bore on the ground. Cue the dog to enter the tunnel and lie down on the platform, C/T. Cue the dog to "rest" and C/T for any duration of chin targeting to the foam chin rest inside the bore on the ground.
      1. Conduct subsequent sessions with the mock bore elevated 3'. Invite the dog to jump or lift the dog into the elevated bore, C/T.
      2. Cue the dog to lie down, C/T.
      3. Cue the dog to "rest" and C/T for 1-12 s of chin contact to the foam chin rest in the elevated bore.
      4. Repeat this session until the dog will chin target for at least 16 s; each session should last between 5 and 15.
   2. Elevated chin rest with increasing duration. Invite the dog to jump or lift the dog into the mock bore. Cue the dog to lie down, C/T.
      1. Cue the dog to "rest" and C/T for 1-12 s of chin targeting to the foam chin rest in the elevated bore.
      2. Build duration to 60 ss. Increments can be 1"-12", 16"-23", 26"-45", 60"+.
      3. Repeat this session until the dog will chin target for at least 60 s; each session should last between 5 and 15 min.
   3. Introduce mock radiofrequency (RF) coil with no elevation and reduced duration. While seated on the ground beside the mock RF coil and foam chin rest, C/T the dog for any investigation (i.e., sniffing, close proximity, orientation towards) of the apparatus.
      1. Cue the dog to "rest" and use a nose touch or food lure to guide the dog's head into and through the mock RF coil onto the foam chin rest and C/T for 1-5 s of chin contact.
      2. Build duration to 30 s. Increments can be chin rest for 1"-5", 6"-12", 16"-26", 30"+.
      3. Repeat this session until the dog will chin target through the mock RF coil for 30 s; each session should last between 5 and 15 min.
   4. Elevated chin rest in mock RF coil. With the mock RF coil and foam chin rest inside the mock bore, invite the dog to jump or lift the dog into the bore.
      1. Cue the dog to lie down and "rest", and C/T for 1-5 s of chin contact.
      2. Build duration to 50 s. Increments can be 1"-5", 6"-12", 16"-26", 28"-37", 50"+.
      3. Repeat this session until the dog will chin target to the foam chin rest through the mock RF coil in the elevated bore for 50 s; each session should last between 5 and 15 min.
   5. Elevated chin rest in mock RF coil with increasing distraction and duration. With the mock RF coil and foam chin rest inside the mock bore, invite the dog to jump or lift the dog into the bore.
      1. Cue the dog to lie down and "rest", and C/T for 1-12 s of chin contact.
      2. Gradually add visual and acoustic distractions. Build duration to 100 s (1'40") with and without distraction.
      3. Increments can be 1"-12", 16"-37", 41"-60", 66"-88" (1'6"-1'28"), 100"+ (1'40"+).
      4. Repeat this session until the dog will chin target for 100 s; each session should last between 5 and 15 min.
   6. Introduce ear padding, duration initially reduced. Lift or invite the dog to jump into the bore, cue "down," outfit him with ear padding, and C/T for any duration of tolerating the ear padding without excessive movement.
      1. Cue "rest," and C/T for 1-5 s of chin contact. Build duration to 60 s. Increments can be 1"-5", 6"-26", 28" 45", 60"+.
      2. Repeat this session until the dog will chin target in the mock bore with ear padding for 60 s; each session should last between 5 and 15 min.
   7. Elevated chin rest in mock RF coil with ear padding and increasing duration and distraction. Lift or invite the dog to jump into the bore, cue "down" and "rest," outfit him with ear padding, and C/T for 1-12 s of chin contact.
      1. Gradually add visual and acoustic distractions. Build duration to 107 s. Increments can be 1"-12", 16"-37", 41"-60", 66"-88", 107"+.
      2. Repeat this session until the dog will chin target in the mock bore with ear padding for 107 s; each session should last between 5 and 15 min.
   8. Introduce scanner noise. Lift or invite the dog to jump into the bore, cue "down" and "rest," and outfit it with ear padding.
      1. Play scan audio at a barely audible volume between 0-40 dB and C/T for 1-12 s of chin contact.
      2. Build duration to 107 s. Increments can be 1"-12", 16"-37", 41"-60", 66"-88", 107"+.
      3. Repeat this session until the dog will chin target in the mock bore with ear padding and up to 40 dB scan audio for 107 s; each session should last between 15 and 30 min.
   9. Build duration to 2 min 30 s with increasing distance. Lift or invite the dog to jump into the bore, cue "down" and "rest," and outfit him with ear padding.
      1. Play scan audio between 41 and 70 dB and C/T for 1-37 s of chin contact. Gradually add distance, moving around the mock bore, out of sight then back into sight of the dog.
      2. Build duration to 142 s. Increments can be 1"-37", 41"-88", 97"-107", 117"-129", 142"+.
      3. Repeat this session until the dog will chin target in the mock bore with ear padding and 41-70 dB scan audio for 142 s, with and without distraction and distance; each session should last between 15 and 30 min.
   10. Build duration to 4 min. Lift or invite the dog to jump into the bore, cue "down" and "rest," and outfit him with ear padding.
       1. Play scan audio between 60 and 90 dB and C/T for 1-107 s of chin contact.
       2. Build duration to 240 s. Increments can be 1"-107", 117"-142", 156"-189", 208"-229", 240"+.
       3. Repeat this session until the dog will chin target in the mock bore with ear padding and 60-90 dB scan audio for 240 s, with and without distraction and distance; each session should last between 15 and 30 min.
   11. Build duration to 5 min. Lift or invite the dog to jump into the bore, cue "down" and "rest," and outfit it with ear padding.
       1. Play scan audio between 80 and 110 dB and C/T for 1-120 s of chin contact.
       2. Build duration to 300 s. Increments can be 1"-120", 129"-189", 208"-229", 252"-277", 300"+.
       3. Repeat this session until the dog will chin target in the mock bore with ear padding and 80-110 dB scan audio for 300 s, with and without distraction and distance; each session should last between 15 and 30 min.

3. Transfer

NOTE: 1) Upon reaching final criterion of the stationing behavior in the mock MRI training location (5 min down-stay and chin rest in mock bore and mock RF coil while wearing ear padding, with scanner noise playing at 80-110 dB), the dog undergoes five distinct location transfer (generalization) sessions. During these transfer sessions the dog stations to the above criteria in several indoor and outdoor locations that are as unique as possible, with different sights, sounds, and degrees of social distraction across settings (e.g., secluded grass field, quiet academic building hallway, busy academic building lobby, crowded bus stop, loud water treatment plant)⁸.

1. To assemble the portable Mock MRI used for Transfer, compile a tunnel (regulation agility tunnel, stabilized with sand bags), a plywood platform, an acrylic mock RF receiver coil, the foam chin rest apparatus, and a portable speaker system (see Table of Materials). Affix buffer pads affixed to the interior of the mock RF coil to provide padding against the dogs' ears and additional cranial stabilization/placement feedback.
2. Stand or sit beside the (portable) mock bore with the mock RF coil and chin rest inside. Gesture the dog to enter the bore, cue "down" and "rest," and outfit it with ear padding.
3. Play scan audio at 80-110 dB and C/T for 1-30 s of stationing in the new location.
4. Next, probe for criterion duration (reinforce at 5 min or when the dog breaks).
5. Conduct repeated bouts of 1-5 min chin rest repetitions for 30-60 min.
6. Conduct one 30-60 min session in each location. Once the dog has generalized the stationing behavior to criterion in five distinct transfer locations, the dog is ready for data collection in the real MRI environment.

4. MRI

1. An MRI data collection session takes between 30 and 60-min. Begin the data collection session with a localizer, followed by acquisition of high-resolution anatomical images to serve as a prescription reference using the 3D magnetization-prepared rapid gradient echo (MPRAGE) sequence. Following the anatomical scan, perform the functional Magnetic Resonance Imaging scans (e.g., stimulus presentation and resting state). This MRI protocol represents examples from prior work and is only suggestive (see Jia et al.⁴ and Thompkins et al.¹⁰ for how to perform the protocol).
   1. Give the dogs approximately 1 min breaks with their reward outside of the scanner between scans.