Dr. Karten's research activities have led to a greater appreciation of the importance of evolutionary analyses of nonmammalian brains (both vertebrates and invertebrates) at a cellular, circuit, and molecular level. Important findings continue to produce shifts in perspective regarding the organization of the brain in nonmammalian vertebrates, sensory organization of ascending paths, their evolution, and their consequences for understanding the human brain.
Current research focuses on studies of the neural circuitry, biophysics, and evolution of motion detection in birds and mammals. The Karten laboratory has provided a radically new basis for understanding the underlying mechanism of motion detection as a product of the three-dimensional morphology of the tectal ganglion cells, their retinal inputs, modulatory inputs from the brainstem, the biophysics of individual cells, and the ion channels underlying their unique responses to moving stimuli.
The laboratory also published a series of studies regarding the ontogeny of these neurons and developed a number of new methods for clarifying these issues. These studies led to a further examination of the topography of the projections of the tectal ganglion cells upon the thalamus. The group discovered that the tectal ganglion cell motion detection response is based on a unique micro-architecture of responsive points with intervening unresponsive areas. This produces the "motion" signal, but without evident directionality.
In the course of this work, the group also discovered a unique and most unusual pattern of organization of the pigeon tectum, described as an "interdigitating topographic arrangement." Parallel studies in mammals have demonstrated that the 3D morphology, laminar distribution, retinal ganglion cell inputs, and subtypes of tectal ganglion cells, in the squirrel optic tectum are virtually identical to those found in birds.
Subsequent studies of retinal projections in squirrels revealed that the tectum of squirrels and birds show identical patterns of cell typologies and lamination, contrary to a long-held opinion regarding the irreconcilable differences between the tectum of birds and mammals (Dan Major, PhD thesis, 2003). This analysis will permit wider use of the chick tectum in understanding the fundamental pattern of organization, function, and development of the ascending tectal pathways in all vertebrates, including mammals.
Dr. Karten's other activities involve participation, with Professor E.G. Jones at the UC Davis Center for Neuroscience, in the Human Brain Project. Dr. Karten has been credited with advancing the development of a vector-based digitized brain atlas of the pigeon and is currently working on a similar project on chicks and monkeys. This is part of a larger effort to develop a cell-based database of brain regions, neurons, connections, and chemical properties.
Dr. Karten's long-term work on the nature of the bird forebrain and the evolutionary relationships of the avian telencephalon and the mammalian neocortex was highlighted at the International Avian Brain Conference, held at Duke University in 2002. Also, in an article titled "Birds and Babes," Dr. Karten was featured in the San Diego Union Tribune (September 3, 2003). Dr. Karten states that "the bird may be the very best model we have, both neurologically and behaviorally, for vocal control systems."
Dr. Karten provides both formal coursework and mentoring to individual students. He is an active participant in the Graduate Program in Neurosciences. He offered Principles of Digital Imaging during 1999, 2000, and 2001 as part of "Boot Camp," an intensive two-week laboratory and lectureship program for incoming graduate students.
Dr. Karten serves on the Scientific Editorial Board of the Journal of Comparative Neurology and is a frequent reviewer for such esteemed journals as Science, Journal of Neuroscience, Journal of Comparative Neurology, and Brain Research. He also regularly provides reviews for NSF (Neurobiology), NIMH, NINDS, and NEI.
Dr. Karten maintains other faculty appointments at the UCSD Department of Psychiatry, the Scripps Research Institute, and the University of Utah. In 2003, he was honored by Cal Tech as Visiting Distinguished Wiersma Professor. Additional honors include the 2005 Krieg Cortical Discoverer award from the Cajal Club and his April 2006 presentation, "Unwiring the Brain: Neuromorphic Engineering of Motion Detection," for the Annual Rockwood Memorial Lecture at the UCSD Institute for Neural Computation.