[1] Univ Kentucky, Coll Med, Dept Neurosci, Lexington, KY 40536 USA
[2] Univ Kentucky, Coll Med, Dept Physiol, Lexington, KY USA
[3] Univ Kentucky, Coll Med, Sanders Brown Ctr Aging, Lexington, KY 40504 USA
[4] Univ Kentucky, Coll Med, Dept Neurol, Lexington, KY USA
[5] Univ Kentucky, Coll Med, Dept Radiol, Lexington, KY USA
[6] Univ Kentucky, Coll Med, Magnet Resonance Imaging & Spect Ctr, Lexington, KY 40536 USA