The visual perceptual process begins one synapse from the eye, in the primary visual thalamus (LGN) - the sole link between eye and cortex. Intriguingly, 90% of synaptic inputs to the LGN do not originate from the eye; most arise from brain regions encoding internal states. A major source of such input originates from the dorsal raphe nucleus (DR), a critical center for reward and satiety, suggesting that DR-LGN feedback may modulate responses to rewarding visual stimuli. However, the function, behavioral significance, and wiring of DR-LGN projections is uncharacterized. To learn more about how DR-LGN circuitry shapes the perceptual process in mice, we built several head-fixed virtual reality arenas where mice are presented with checkerboard noise from which a grating stimulus emerges; grating detection results in a juice reward. Mice learn to detect stimuli of varying saliency according to classical psychometric relationships. We are now performing fiber-photometric recordings from behaving mice whose DR neurons express genetically encoded calcium indicators (gcamp6f) to search for neural correlates. Our current results indicate that DR activity is linked to rewarding stimuli and tracks the appearance of the grating stimulus. To provide further insight, mathematical models were constructed to generate hypotheses on how the DR circuitry is arranged. These studies are the first to define how DR-LGN feedback regulates visual behavior.