EDITORS CHOICE IN NEUROSCIENCEThe paperJ. Bauer et al., “Limited practical merging of eye-specific inputs in the retinogeniculate pathway of the mouse,” Neuron, 109:2457– 68. e12, 2021. Mice have binocular vision, but unlike in people, the visual fields of their side-facing eyes have little overlap. Researchers once speculated that many neurons most likely gotten input from just one retina, but current research study has shown that a surprising variety of nerve cells in the visual thalamus connect to both eyes. “This is a little a joke in the field,” states Tobias Rose of limit Planck Institute of Neurobiology in Germany. “The mouse is very sloppy in its electrical wiring; it simply wires whatever up with everything.” Nerve fibers from both eyes cross over to the other side of the brain in mice. © Max Planck Institute of Neurobiology/ BauerTo untangle these unpleasant connections, Rose and his team studied modifications in electrical activity in the murine visual thalamus as it was stimulated optogenetically with blue or red light, validating the cross-wiring to both eyes. They then exposed mice to intense flashes and moving checkerboard patterns while keeping track of brain activity. The scientists discovered that the visual thalamus silenced redundant input in approximately 99 percent of the visual neurons– while the cells got signals from both retinas, only one signal was sent out to the cerebral cortex. These outcomes challenge the understanding of the visual thalamus as a simple relay, where an input induces a consistent output. “A relay is not expected to be plastic; if its plastic, its not a relay by meaning,” says Rose. More research is needed to determine how the thalamus silences visual signals, and Rose states there are likely numerous mechanisms. ” It was a really sophisticated study, the way they specifically resolved the relative input of the two eyes onto single neurons,” states Lindsey Glickfeld, a neurobiologist at Duke University who was not included in the research. She adds that this research study verifies previous findings and reminds neurobiologists that “even if the connection is there, [it] does not inform you how strong it is.”
Scientists as soon as speculated that many neurons most likely received input from just one retina, but recent research has revealed that an unexpected number of nerve cells in the visual thalamus link to both eyes. © Max Planck Institute of Neurobiology/ BauerTo untangle these untidy connections, Rose and his team studied modifications in electrical activity in the murine visual thalamus as it was stimulated optogenetically with blue or red light, confirming the cross-wiring to both eyes. These results challenge the understanding of the visual thalamus as an easy relay, where an input causes a consistent output.
