All ETDs from UAB

Advisory Committee Chair

Lawrence C Sincich

Advisory Committee Members

Timothy W Kraft

John M Laurent

Document Type


Date of Award


Degree Name by School

Master of Science (MS) School of Optometry


Despite advances in the understanding of the primate visual system, much is yet to be learned about the way light signals sum to create our perception of the world. This is especially true at the simplest level of visual processing—the summation of two individual cone photoreceptor signals. How such signals combine to create visual perception has not been assessed in vivo. We used an adaptive optics scanning laser ophthalmoscope (AOSLO) to deliver binarized noise movies to identified groups of cones within the receptive fields of neurons in the macaque lateral geniculate nucleus (LGN). Recordings of neural action potentials within the LGN allowed us to see how cone signals modulate the firing rate in the presence of ongoing activity, as is typical of real life visual scenes. Given two stimulus pixels within a receptive field center, we show linear changes in the probability of action potentials in LGN neurons when cones are stimulated pairwise rather than alone. This linearity occurred for both positive and negative contrasts in the 4 LGN neurons analyzed. These data demonstrate that linear summation can occur between photoreceptors, most likely originating in early retinal circuitry.

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