Most of what neuroscience knows about vision in mammals comes from the laboratory mouse, a nocturnal animal with modest eyesight, studied by a species that navigates the world in daylight. Researchers at the Universidad de Chile's Department of Biology, in an international collaboration with the University of Massachusetts Amherst, propose a local alternative: the degu, a diurnal Chilean rodent. Their study, led by postdoctoral researcher Natalia Márquez with colleagues including Gonzalo Marín and Jorge Mpodozis, appeared in the Journal of Neurophysiology.
The work delivers the first characterisation of visual responses in the degu's superior colliculus, a midbrain hub for visual orienting. The team probed responses to moving patterns, contrast changes, sinusoidal gratings and expanding shapes simulating an aerial predator, and found the degu's visual acuity exceeds that of other rodents. The animal's biology stacks the deck: it is active by day, born with open eyes, and carries a retina with two cone types and a high density of ganglion cells favouring spatial resolution.
The authors are explicit that the point is comparative rather than biomedical: the question is whether the mouse, chosen for convenience and genetics, is really the right model for understanding daytime vision of the human kind. The Santiago group's next phase will raise degus in complete darkness to measure how much of the visual system's development depends on light experience, a classic question now being asked in a new animal.