Saturday, May 17, 2025
5/17/2025
Elementary Cone Photoreceptor Representation in Primary Visual Cortex - Project Summary/Abstract Primary visual cortex (V1) is the key cortical area in the brain that establishes how visual perception operates in humans. Its central importance arises from two facts: V1 receives the majority of the signals generated by the retina and it establishes the dissemination of different types of visual information to higher cortical areas in the brain. Many previous studies have characterized the response properties of single V1 neurons, however all of them were conducted using the eye's natural optics, which are subject to optical aberrations. Such aberrations can lead to confounds between wavelength, orientation, and spatial frequency in visual stimuli, in particular at or near the fovea where these parameters are the most difficult to control. Using adaptive optics technology, we will overcome the limits imposed by optical aberrations in order to measure V1 neural responses at a cone-resolved level in the non-human primate for the first time. Several fundamental questions will be answered: (1) How many cone photoreceptors comprise a V1 neuron's receptive field near the fovea, and what cone types are they? (2) What is the elementary response of a V1 neuron to signals provided by a single cone? (3) How many V1 neurons receive input from a single cone? In the high spatial frequency domain needed to answer these questions near the fovea, we will be able to optically separate the parameters of wavelength and geometric orientation in order to also address a major unanswered question about how the visual signaling pathways in cortex are initially segregated: Do the populations of V1 neurons that project differentially to secondary visual cortex (V2) receive input from different cone compositions? These questions will be answered in tandem with a series of experiments that will additionally allow us to assess the impact of cone signal loss, as a model of what occurs in retinal degenerative diseases. By asking how resilient V1 responses may be in the face of synthetically degraded stimuli, we will learn if there is a V1-based mechanism behind why perceptual deficits in patients are often not as severe as retinal imaging of diseased tissue indicates. Our results will establish the basic signaling properties of cone photoreceptors as seen by V1 neurons and potentially reveal a cortical signature for perceptual “filling-in” at the single neuron level. Both of these outcomes will substantially improve our understanding of visual processing and create a new path for earlier detection of retinal disease. 1
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