Performance and Behavioral Flexibility on a Complex Motor Task Depend on Available Sensory Inputs in Early Blind and Sighted Short-Tailed Opossums

Abstract

The early loss of vision results in a reorganization of visual cortex, which becomes commandeered by the somatosensory and auditory systems. Recent studies in the short-tailed opossum found that the connections and response properties of neurons in somatosensory cortex of blind animals are also altered. While studies in humans and other mammals show that early vision loss leads to heightened abilities on discrimination tasks involving the spared senses, if and how this superior discrimination leads to adaptive sensorimotor behavior has yet to be determined. Moreover, little is known about the extent to which blind animals rely on the spared senses. Here, we tested opossums on a sensorimotor task involving somatosensation. We found that early blind animals had increased limb placement accuracy compared to sighted controls, while showing similarities in crossing strategy. Whisker trimming nullified this advantage, resulting in decreases in limb placement accuracy and more variable forelimb movements in both groups. However, the increased reliance on tactile inputs in early blind animals led to greater deficits in limb placement and behavioral flexibility when the whiskers were trimmed. This data demonstrates that incoming sensory input from the whiskers is processed differently in the brains of early blind compared to sighted opossums, likely due, in part, to the dramatic changes to visual and somatosensory cortex. These results also provide direct evidence for the prevailing theory that the whiskers are critical for skilled forelimb control in whisking mammals, and highlight the importance of studying both performance and strategy when assessing differences in behavior.