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Matthew Harper, Frederick Blodi, Malini Shankar, Elena Hernandez-Merino, Helga Kecova, Laura Dutca, Randy Kardon, Steven Stasheff; Retinal ganglion cells exhibit spontaneous hyperactivity and abnormally sustained light-evoked responses in in a mouse model of traumatic brain injury. Invest. Ophthalmol. Vis. Sci. 2013;54(15):4570.
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To characterize the in vivo and in vitro function and structure of retinal ganglion cells after blast-mediated traumatic brain injury.
Blast injury was produced by exposing mice to a 20 psi overpressure wave produced by rupture of a Mylar membrane in a specially constructed compressed air tank. Pattern ERG (pERG) was used to objectively measure in vivo retinal ganglion cell (RGC) function at various time-points after injury (n=79). Multielectrode recordings from in vitro whole-mounted retinas (n=4, 75 RGCs/retina) were used to evaluate the properties of individual RGCs. For each RGC the average spontaneous discharge rate and responses to both simple and complex stimuli were compared with retinas from non-blasted control mice.
The pERG declined with a biphasic time course, with initial deficits resolving by 24h post injury and chronic deficits reappearing 4 months following blast exposure. Multi-electrode recordings 7d following blast demonstrated normal RGC responses. By 37d following injury, sustained spontaneous RGC hyperactivity had developed. A substantial proportion of RGCs had prolonged or otherwise aberrant light-evoked responses. Some computed receptive fields were also enlarged and shallow relative to retinas not exposed to blast injury.
In this model, TBI induces dramatic changes in spontaneous and light-evoked retinal ganglion cell activity, beginning several weeks after an initial period of normal physiology. These changes precede decreases in pERG amplitude and changes in RGC morphology. The increased spontaneous activity and prolonged responses to light may be interpreted as “noise” in the retina’s message to the brain, which may underlie varied complaints of distorted visual perception by TBI victims.
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