Michael S. Loop, Ph.D.
Primary Department Affiliation: Vision Sciences
Primary Research Area: Systems Neuroscience and Vision
Recently, my research has been directed at understanding the relationship between visual perception and nervous system activity. Under light adapted conditions, normal humans can generally see the color of a spectral increment at detection threshold. Several known, and suspected, features of the normal human visual system may account for our excellent color vision.
We have a cone dominated fovea, three cone types, and an abundance of wavelength opponent neurons. Further, wavelength opponent neurons have a natural sensitivity advantage over non-wavelength opponent neurons; some wavelengths will put excitation at an advantage over inhibition. Which, or how many, of these features determine color vision sensitivity is being investigated. Our approach is to study the color vision sensitivity of human dichromats and non-human animals which possess particular features in common with normal humans. Recently we have found that goldfish, macaque monkey, chipmunk, ground squirrel and tree shrew also detect the color of threshold photopic spectral increments. By some measures, human dichromats also detect photopic spectral increments with wavelength opponent neurons but they do not detect the color of the flash at detection threshold. This suggests that human dichromats may have abnormal central processing of color information in addition to their missing retinal photopigment. A return to studies of reptile sensory processes is ongoing.
Hartline, PhD., L. Kass and M.S. Loop. 1978, Merging of modalities in the optic tectum: infrared and visual integration in rattlesnakes. Science, 199:1225-1229.
Loop, M.S. and L.L. Bruce, 1978, Cat color vision: The effect of stimulus size. Science, 199:1221-1222.
Loop, M.S., C.L. Millican, and S.R. Thomas. 1987. Phototopic spectral sensitivity of the cat. J. Physiol., 382:537-553.
He, J. and M.S., Loop. 1992. Spectral sensitivity of monocularly deprived cats. Vis. Res., 9:617-622.
Ooi, T.L., and M.S. Loop. 1994. Visual suppression and its effect upon color and luminance sensitivity. Vis. Res., 34:2997-3003.
Loop, M.S. and D.K. Crossman. 2000. High color vision sensitivity in macaque and humans. Vis. Neurosci., 17:119-125.
Loop, M.S., J.F. Shows, S.C. Mangel and T.K. Kuyk. 2003. Colour thresholds in dichromats and normals. Vision Research, 43: 983-992.
Van Arsdel, R.E. and M.S. Loop. 2004. Color vision sensitivity in normally dichromatic species and humans. Visual Neuroscience, 21: 685-692.
Roberts, C.M. and M.S. Loop. 2004. Goldfish color vision sensitivity is high under light adapted conditions. Journal of Comparative Physiology A, 190:993-999.
Michael S. Loop (b.1946), Associate Professor, Department of Vision Sciences and Neurobiology. He completed his studies in psychobiology at Florida State University (B.S., 1968; M.S., 1971; Ph.D., 1972). A portion of his postdoctoral work was undertaken at the University of Virginia studying central visual system function with Dr. John A. Jane (Neurosurgery) and Dr. S. Murray Sherman (Physiology).
Following this he moved to the University of Illinois and collaborated with Dr. Peter H. Hartline (Physiology and Biophysics) on infrared detection in snakes. Since 1978 he has been on the faculty at UAB. His spare time is committed to yard work, children and fishing.