1. Lawson Health Research Institute, St Joseph's Health Centre and University of Western Ontario, 268 Grosvenor Street, London, ON, N6A 4V2, Canada
2. National Research Council Institute of Clinical Physiology, Via Sari 8, 56126 Pisa, Italy
3. Lawson Health Research Institute, Department of Nuclear Medicine and Magnetic Resonance, St Joseph's Health Care and University of Western Ontario, London, ON, N6A 4L6, Canada
4. Department of Ethology, Ecology and Evolution, University of Pisa, 56126 Pisa, Italy