Profile - Louis J. Toth, Ph.D.

Research Interests
My research focuses on studying how small ensembles of neurons in the mammalian brain code information and work together to solve simple computational problems.  This question is approached both by studying how the brain codes sensory inputs, using the visual system as a model, and by studying how the brain modulates its coding in response to behavioral demands, using animals trained to solve cognitive tasks.  I currently use the following techniques:
Magnetic resonance
Recent advances in MR imaging enable the mapping of brain physiology and anatomy in animals without surgical intervention.  Ongoing research at the University of Minnesota Center for Magnetic Resonance Research and the new Biomedical Imaging facility at BUSM focuses on measuring and improving the spatial accuracy of diffusion tensor imaging (DTI) and functional imaging methods (fMRI). (Collaborators: Dae-Shik Kim, Itamar Ronen, Kamil Ugurbil.) 
Camera-based imaging of neural activity in visual cortex
In experimental preparations, neural activity can be directly imaged using intrinsic signal and voltage-sensitive dye techniques.  Visual stimuli can be used to elicit physiological maps of, for example, retinal position, orientation or ocularity, and these maps can be used to probe the functioning of cortical circuits under various experimental conditions.
Transcranial magnetic stimulation
TMS is a safe way to stimulate human brain tissue non-invasively, and has many potential clinical applications.  A variety of techniuqes are being used to directly visualize neural activity resulting from TMS in order to better understand how to design effective treatments.  (Collaborators: Tony Valero, Bertram Payne, Alvaro Pascual-Leone.)
Single-unit recording in the behaving macaque.
Hypotheses about cortical computation are tested by recording activity in single neurons from monkeys trained to perform cognitive tasks.  Also being developed for these studies are functional MRI and diffusion tensor imaging from awake and anesthetized primates.
Dr. Toth is course faculty for AN700 - Medical Histology
Scientific Background
Dr. Toth received a Ph.D. from the Department of Brain and Cognitive Sciences at the Massachusetts Institute of Technology.  In the lab of Dr. Mriganka Sur, Dr. Toth developed techniques of whole-cell recording and intrinsic signal imaging to visualize neuronal activity in normal adult visual cortex.  Dr. Toth did postdoctoral work with Dr. John Assad in the Department of Neurobiology at Harvard Medical School.  There, he trained monkeys in tasks designed to test specific hypotheses about how neurons in associative areas of parietal and temporal cortex encode relevant behavioral information

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Comments  |  4 Sept 2003