Adaptive Control of Innate Reflexes by Visual Cortex



Time: 14:00-15:30  on Mon., Jan. 22, 2018
Venue: B323, Medical Science Building, Tsinghua University


Speaker: Dr. Baohua Liu
Assistant Professor, Department of Biology, University of Toronto Mississauga
Host: Dr. Kexin Yuan

    The mammalian visual cortex sends massive axonal projections to the brainstem, including projections to nuclei that mediate innate motor reflexes. These long-range projections represent an anatomical substrate through which visual cortex may directly influence innate behaviors. To test this hypothesis, I studied the impact of visual cortex on the optokinetic reflex (OKR), an involuntary eye movement that stabilizes images on the retina while the animal moves.
     Although innate, the OKR is highly plastic. This plasticity is essential to maintain image stability, since the amplitude of the OKR needs to be continuously readjusted as the animal matures, grows, ages or suffers from impairments of other ocular motor reflexes. Previously, OKR plasticity was thought to be entirely mediated by the brainstem and cerebellum. However, I discovered a prominent role of the visual cortex in this plasticity. In particular, I showed that a plastic increase in the amplitude of the OKR, induced by impairing another image stabilization mechanism, was reversed upon silencing visual cortex.
    Furthermore, I discovered that by selectively ablating visual cortical neurons projecting to the brainstem nuclei responsible for the OKR, I could strongly reduce OKR plasticity. Finally, I showed that OKR plasticity is generated by an enhanced drive exerted by visual cortex onto these brainstem nuclei. These results demonstrate how the innervation of a phylogenetically older structure by the neocortex can modulate and expand the performance of reflexive behaviors in an experience dependent manner.


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