*Most of the information presented below is (shamelessly) taken from my PhD advisor, Dr. Jody Culham's excellent webpage.
What is functional MRI?
Magnetic resonance imaging (MRI) is a technique that uses a strong magnetic field and low-energy radio frequency waves to obtain a picture of the anatomy. Functional MRI uses the same type of scanner that is used for patients receiving an MRI scan. However, fMRI images the level of oxygen in the blood to determine which areas of the brain are active when subjects are working with different stimuli or tasks. MRI and fMRI do not involve any radiation, x-rays, or drugs.
To be eligible to participate, you must:
- have no metal in your body (fillings are okay)
- not be claustrophobic
- be able to remain practically motionless for periods of 5-8 minutes
- be in good health and have no history of neurological disorders (e.g., epileptic seizures, head injuries)
- be able to see without glasses (contacts are okay) at arms' length (I do mostly action-related experiments where you interact with objects within arms' length)
Information for First-time fMRI subjects:
The vast majority of MRI scans are performed without incident; there is no effect on biological tissue. However, working in the presence of a strong magnetic field requires constant viligence to ensure that no ferromagnetic objects enter the scanner room, as they will be pulled toward the centre of the bore with great force. Also, metal that is implanted in your body (i.e. pacemakers, aneurysm clips) may malfunction within the magnetic field. You must fully comply with all safety and screening procedures.
The day of the scan:
- If applicable, remember to wear contact lenses instead of glasses.
- Do not drink excessive amounts of liquid, especially caffeine (a diuretic -- an fMRI session seems much longer with a full bladder!).
- Do not wear any shirts with metal around the head (e.g., pullovers with zippers). Metal buttons and zippers on pants are okay.
- Do not use any hairclips and be prepared to remove jewellery.
- For women, if possible, do not wear an underwire bra (the metal can throw off the magnetic field). Sports bras are usually good and we have hospital gowns to change into if necessary. The clasps on the back of a regular bra are not a problem, but avoid wearing bras that have metal parts on the straps.
- Avoid wearing mascara (can contain metal flakes), hair gel (can throw off magnet signal) and wet hair.
- Make sure you know where you are going to meet the experimenter and what time you are expected to show up. See Directions Here
- If anything comes up such that you cannot make your scheduled time, notify the experimenter as soon as possible!!!. Scan time costs $300/hour regardless of whether or not the subject shows up.
***Queen's MRI scanner Location & control room phone number: (613) 533-6000 x32811
While in the magnet:
- So as not to be alarmed, during operation the scanner will make loud beeping noises and pulsing sounds. In order to protect your hearing you will be given a set of headphones to wear. These headphones, in addition to muffling the sounds of the scanner, will also be used to deliver auditory cues to you throughout the experiment (e.g., "grasp the object on the left").
- If you notice anything vaguely uncomfortable before you get rolled into the magnet, tell the experimenter. Things that are slightly uncomfortable at the start of the experiment will become excruciating by the end! Once you are in place, you will maintain that exact position for a couple hours. As such, I highly encourage participants to complain as much as possible about any potential discomfort prior to being rolled into the scanner.
- As the bed is moving into the center of the bore, moving through the magnetic field may play tricks on your vistibular system and some people feel a bit dizzy. This is normal, and will subside shortly after the bed stops moving.
- Make a conscious effort not to change head or body position during the entire scan session -- even when the scanner isn't running! While the scanner is running, if the head moves, it creates artifacts that are usually difficult if not impossible to fix. Also, even if the scanner isn't running, small adjustments of the head can create problems in alignment across multiple scanning runs. Furthermore, the position of body parts in the magnetic field distorts it. So if you cross your legs, scratch your head, open your mouth, yawn (inhale deeply), or shift your posture, it can lead to significant artifacts even if your brain doesn't move. Because of this, we make great efforts prior to scanning to make sure that you are as comfortable as reasonably possible. For us, movements on the order of millimeters matter; do your best not to do anything that will move your head from its original position.
- Swallowing can lead to head motion artifacts. If you can avoid swallowing during a scan, the data quality will be better. If trying not to swallow makes you gag or swallow suddenly, then it's best to just swallow normally.
- We try to keep runs as short as possible (ideally under 8 minutes) so that you can stay attentive during the scan. We also try to provide 2-3 minutes rest in between scans so that you can relax your eyes.
- Try to stay relaxed throughout the session. If you tense up at the beginning of a scan, your head can drift as you settle down.
- If you notice anything weird with the stimuli (e.g., they're upside down or you can't see the display or the screen saver comes on partway through a scan) or have problems with the task (e.g., make mistakes, fall asleep), be sure to tell the experimenter after the scan in which it happened.
- If for some reason you fumble with the object and/or perform the task incorrectly on a particular trial, don't worry about trying to correct/fix the problem; just simply prepare for the next trial. The experimenter will retrieve the object at the end of the scan.
- You will be given a squeeze ball in case you need to stop the scan midway. You can use this if something goes wrong with the stimuli or if you need to stop immediately.
Typical setup of the types of action-related experiments we perform.
A) Experimental setup shown from the side view. The subject's head is tilted to permit direct viewing of objects presented on a platform that saddles over the subject's hips. Different sets of LEDs illuminate the object and provide fixation points. Auditory instructions indicating the tasks participants are required to perform are delivered through headphones.
B) Experimental setup shown from the subject's POV (Left). Subjects fixate upon an LED (denoted here as a green star) and view an object presented on the platform. Subjects are then given some auditory cue instructing them on how to act upon the object. Then, following a brief delay period, subjects are finally cued (via an auditory beep) to perform the instructed hand movement (for examples of such hand actions, see right).