William Joseph Schwartz (born March 28, 1950) is an American neurologist and scientist who serves as Professor and Associate Chair for Research and Education in the neurology department at the University of Texas Dell Medical School.

In 1977, Schwartz, along with Harold Gainer, Ph.D,[7] found that the glucose consumption in the rat suprachiasmatic nucleus is a function of time of day and environmental lighting conditions.

This insight has been key to the interpretation of modern brain mapping methods, including 18 F-DG PET scanning and the BOLD signal of functional MRI.

This work contributed to establishing suprachiasmatic nucleus c-Fos as the first photoinducible molecular marker and was critical in the process of determining the necessary substrates of the photic entrainment pathway in mammals.

They focused on tissue, organismal, and supra-organismal levels of analysis to see how individual processes interact in the circadian system to produce observable emergent properties.

[1] The Schwartz lab investigated light induced and endogenous gene expression, and the underlying dual oscillatory structure of the circadian pacemaker.

His research, conducted with Matthew J. Paul ad Premananda Indic suggests that cohabitation affects the onset of rhythmicity in hamsters, and that changing the speed of the circadian clock is one mechanism by which social factors could alter daily rhythms.

[9] In a 2013 paper co-authored with Guy Bloch, Erik D. Herzog and Joel D. Levine, Schwartz shows that social cues may be critical to the adaptive function of circadian rhythms, and can affect them from colony, to organismal, to cellular levels.