Predictive Motion Encoding Begins in the Retina

Article: Retina ‘hardwired’ to predict path of moving objects
Source: University of Washington Medicine, via Neuroscience News  and NEI
Published: August 2, 2021

Predictive motion encoding is an aspect of visually guided behavior that allows animals to estimate the trajectory of moving objects. New research shows that information to predict the path of a moving object is generated at the level of the retinal ganglion cells well before the information is relayed to the visual cortex. To study how this happens, the researchers projected patterns of approaching or receding objects (i.e., whether they appeared to be moving either away from or toward the retina) and recorded the signals generated by the ganglion cells in response to the movements, analyzing the signals for patterns reflective of predictive motion encoding. The researchers then compared the performance of the ganglion cells to computer programs created to solve such problems, and found the the retinal ganglion cells were nearly as effective as the computer programs at transmitting predictive information. The authors state, "We report here that four of the parallel output pathways in the primate retina encode predictive motion information, and this encoding occurs for several classes of spatiotemporal correlation that are found in natural vision...[T]hese neural circuit mechanisms efficiently separate predictive information from nonpredictive information during the encoding process." They speculate that the predictive information is made possible by crosstalk among the bipolar cells upstream from the retinal ganglion cells. When one bipolar cell receives an excitatory signal from the photoreceptors upstream from it, in addition to relaying that information to the retinal ganglion cells, it also relays some of the excitatory signal to adjacent bipolar cells. These neighboring cells are then "primed" so that when they receive an excitatory signal from their own photorceptors, they are more likely to send a strong signal to the(ir) retinal ganglion cell. In this way, as a moving object passes over a visual field, information about that movement "ripples" through the network of bipolar cells. Ultimately, the retinal ganglion cells gather the information from the many bipolar cells and encodes it into signals to relay to the visual cortex, which in turn processes the information to predict the path of the object.

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Liu B, Hong A, Rieke F, et al. "Predictive encoding of motion begins in the primate retina." Nature Neuroscience.  24:1280-1291. 2 August 2021. https://doi.org/10.1038/s41593-021-00899-1