1. Department of Neurology, Karolinska University Hospital, Stockholm, Sweden
2. Department of Clinical Neuroscience, Karolinska Institutet, Stockholm, Sweden
3. Institute of Cognitive Sciences and Technologies, C.N.R, Rome, Italy
4. Department of Medical Radiation Physics and Nuclear Medicine, Karolinska University Hospital, Stockholm, Sweden, and
5. Unit of Integrative Epidemiology, Institute of Environmental Medicine, Karolinska Institutet, Stockholm, Sweden