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Research studies of ON-type direction-selective ganglion cells may originate from some forms of nystagmus.

Researchers at the Herbert Wertheim School of Optometry and Vision Science, Science, University of California, Berkeley, have reported a rare type retinal output neurons called ON-type direction-selective ganglion cells (ON-DSGCs).  These ON-DSG cells appear to maintain a stable and clear image of the world, following the direction in which a visual scene is moving and these cells stabilize the gaze thereby reducing image blur while non-primate ancestors move in the environment.  Previous research  thought that the processing of computation on these motion aspects on vision resided in the brain however, more detailed analysis now suggests that specific anatomical data may need to revisit the activity of certain retinal ganglion cells in the retina.  Researchers expect that these findings may impact on the understanding of the human retina, and potentially provides insight into the pathology of eye movement disorders.

Researchers have noted that visual systems, “ranging from flies to humans, have evolved sophisticated gaze-stabilization reflexes that maintain a stable image” of the world during self-motion. These reflexes generate eye movements that track the motion over the visual field, thereby stabilizing the retinal image for certain predators and prey.  Researchers report that these ON-DSGCs are found in lower vertebrates and mammals, and more recently found in primates however, functional implications were not yet fully described.  Researchers expect that many of the dozen or more uncharacterized primate RGC types (retinal ganglion cell) make up only a small fraction (around 1%) of the total RGC population.  More importantly, their recent research underlined a conserved role on the functional, molecular and morphological properties of these types of cells.

DSGCs were discovered in the 1960s in small mammals however, a lack of evidence for these DSGCs in the human retina expected that direction selectivity was computed in the brain. The new evidence suggested that some human gaze stabilization disorders could be linked to abnormal activity within these type of cells themselves (DSGCs).  Their recent paper used state-of-the-art genetic tools, labelling of the neurons with fluorescent markers, and then track them, showing that they had anatomical features. For example, nystagmus is a repetitive, uncontrolled movement of the eyes that can lead to unsteady and blurry vision. They commented that “nystagmus can occur in isolation or can accompany other eye problems such as albinism and certain inherited retinal diseases. While many forms of nystagmus are caused by problems in the brain or inner ear, the results of this study suggest that some forms of nystagmus could originate from abnormal activity of DSGCs in the retina”.