1. Department of Psychology, McGill University, 1205 Doctor Penfield Avenue, Montreal, Quebec H3A 1B1, Canada.
2. Louise and Alan Edwards Centre for Pain Research, McGill University, 740 Doctor Penfield Avenue, Montreal, Quebec H3G 1A4, Canada.
3. Department of Pharmacology and Therapeutics, McGill University, 3655 Promenade Sir-William-Osler, Montreal, Quebec H3A 1Y6, Canada.
4. Department of Anesthesia, McGill University, Montreal, Quebec H3A 1Y6, Canada.