1. VA Portland Healthcare System, Portland, OR, USA.
2. Department of Neurology, Oregon Health & Science University, Portland, OR, USA.
3. Department of Psychology and Program in Neuroscience, Florida State University, Tallahassee, FL, USA.
4. Department of Behavioral Neuroscience, Oregon Health & Science University, Portland, OR, USA.
5. Department of Medicine and Oregon Institute of Occupational Health Sciences, Oregon Health & Science University, Portland, OR, USA.