Berkeley researchers have discovered a rare type of retinal ganglion cell in the eye that are crucial for our visual system to maintain a sharp, steady image of the world. These findings will impact our understanding of the human retina and likely provide insights into the pathology of eye movement disorders.
A human retina labeled with a marker for all retinal ganglion cells in magenta. The sparse subset of retinal ganglion cells involved in gaze stabilization are labeled with a selective marker in green. Image credit: Teresa Puthussery, University of California Berkeley.
The study, recently published in Nature, was led by Teresa Puthussery, O.D., Ph.D., an assistant professor at the Herbert Wertheim School of Optometry & Vision Science and the Helen Wills Neuroscience Institute. First author, Anna Yao Mei Wang, Ph.D., is a postdoctoral scholar in The Puthussery Lab.
The neurons identified are involved in a fundamental feature of everyday vision. As one walks down a busy street or looks out the window of a train, the gaze stabilization system operates below our conscious awareness causing the eyes to reflexively follow the direction in which the visual scene is moving. This visual mechanism works in concert with the vestibular system to maintain a sharp image of a moving world. Clinical conditions that interfere with gaze stabilization can therefore lead to significant visual impairment.
The new findings demonstrate for the first time that retinal neurons underlying gaze stabilization in other mammals are also present in primates, including humans. Neurons that send visual signals from the eye to the brain are called retinal ganglion cells. In humans, there are around 20 different retinal ganglion cell types, each of which responds to specific features of the visual scene, such as form, color, and motion.
The researchers discovered a highly-specialized retinal ganglion cell type known as direction-selective ganglion cells. They respond to motion in the visual field by increasing their activity when movement occurs in their “preferred” direction, while showing little activity to motion in the opposite direction. Collectively, responses from these neurons tell the gaze stabilization system which way the visual scene is moving.