[1] Wake Forest Univ Hlth Sci, Dept Dermatol Neurobiol & Anat & Regenerat Med, Winston Salem, NC 27157 USA
[2] Univ Calif Davis, Dept Sect Neurobiol, Davis, CA 95616 USA
[3] Univ Calif Davis, Dept Physiol & Behav, Davis, CA 95616 USA
[4] Univ Nottingham, Sir Peter Mansfield Magnet Resonance Ctr, Nottingham NG7 2RD, England