Welcome to the Snodderly Lab!
We study the early stages of the primate visual pathway from the retina to the cortex. In human subjects, we are measuring the retinal macular pigment that filters out blue light and protects the fovea from light damage. Perceptual testing and optical imaging allow us to study pigment density in vivo and relate it to color perception and to foveal anatomy. Individual differences in foveal pigmentation and structure may represent different degrees of risk for diseases such as age-related macular degeneration.
For studies of brain function, we train macaque monkeys because they are the best animal models for human vision. In the lateral geniculate nucleus (LGN) and visual cortex, ultrafine electrodes are used to record extracellularly the activity of single and multiple neurons while the monkeys perform tasks that control their behavior. High precision eyetracking and fast stimulus displays enable us to control stimulus position and motion accurately on the retina even in the presence of normal eye movements. We either compensate for the eye movements or record them and measure their effects as needed.
Experiments typically involve careful characterization of the receptive field properties of neurons, including their spatiotemporal and chromatic properties, while compensating for eye movements. A computational model of the cell’s properties may be generated from the results. Then we record neuronal responses during natural viewing of images of natural scenes, such as vegetation or other objects and test the predictions from modeling studies. One goal of these experiments is to learn how eye movements interact with stimulus properties to shape the responses of visual neurons when viewing natural objects.
In a broader context, we are interested in how primate visual systems evolved in response to selection pressures related to foraging for food, and other survival activities. To consider these issues, we observe primates in natural habitats and measure optical properties of their environments and important objects. Our goal is to relate the function and organization of the visual system to the properties of these natural stimuli.