Researchers at the National Eye Institute (NEI) have defined a crucial window of time that mice need to key in on visual events. As the brain processes visual information, an evolutionarily conserved region known as the superior colliculus notifies other regions of the brain that an event has occurred. Inhibiting this brain region during a specific 100-millisecond window inhibited event perception in mice. Understanding these early visual processing steps could have implications for conditions that affect perception and visual attention, like schizophrenia and attention deficit hyperactivity disorder (ADHD). The study was published online in the Journal of Neuroscience. NEI is part of the National Institutes of Health.

“One of the most important aspects of vision is fast detection of important events, like detecting threats or the opportunity for a reward. Our result shows this depends on visual processing in the midbrain, not only the visual cortex”, said Richard Krauzlis, Ph.D., chief of the Section on Eye Movements and Visual Selection at NEI and senior author of the study.

Visual perception – one’s ability to know that one has seen something – depends on the eye and the brain working together. Signals generated in the retina travel via retinal ganglion cell nerve fibers to the brain. In mice, 85% of retinal ganglion cells connect to the superior colliculus. The superior colliculus provides the majority of early visual processing in these animals. In primates, a highly complex visual cortex takes over more of this visual processing load, but 10% of retinal ganglion cells still connect to the superior colliculus, which manages basic but necessary perceptual tasks.

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Image: Slice of mouse brain showing neurons of the superior colliculus highlighted on one side. Image credit: Lupeng Wang, Ph.D. and Charles Gerfen, Ph.D.