Abstract
Modulation of neural responses is frequently observed in the superior colliculus (SC), a retinorecipient midbrain structure that controls orienting and the localization of attention. Although behavioral contingencies that influence SC responses are well documented, the neural pathways and molecular mechanisms responsible for this modulation are not completely understood. Here, we illustrate a dopaminergic system that strongly impacts neural responses in the SC. After using RNA sequencing (RNA-seq) to detail the transcriptome of dopamine-related genes in the SC, we show that D1 receptors are enriched in the superficial visual SC, while D2 receptors segregate to the intermediate multimodal/motor SC. Retrograde injections into the SC consistently label A13, a small dopamine cell group located in the zona incerta. We surmise that A13 mimics dopaminergic effects that we observed in SC slices, which suggests that dopamine in the SC may reduce the tendency of an animal to orient or attend to salient stimuli.
Highlights
Neurons in the superior colliculus (SC) exhibit different responses to the same stimulus based on current behavioral demands (Knudsen, 2011; Basso and Wurtz, 1998; Wurtz and Mohler, 1976; Ikeda and Hikosaka, 2003, 2007)
Single neurons in the largest superficial layer, the SGS, receive converging input from both V1 and retinal ganglion cell axons that terminate along the SC surface in a topographic ‘‘visual map’’ of contralateral space (Sperry, 1963; Phillips et al, 2011; Huerta and Harting, 1984b); these retinal axons enter the SC via the SO ventral to the SGS and give rise to activity in superficial SC neurons that encodes the spatial locations of salient visual stimuli
We describe a dopaminergic modulatory pathway that terminates in the SC, where D1 and D2 receptors are arranged in a behaviorally relevant pattern: D1 receptors are enriched in the superficial visual SC, while D2 receptors are concentrated in the multimodal/motor SC layers
Summary
Neurons in the superior colliculus (SC) exhibit different responses to the same stimulus based on current behavioral demands (Knudsen, 2011; Basso and Wurtz, 1998; Wurtz and Mohler, 1976; Ikeda and Hikosaka, 2003, 2007). Single neurons in the largest superficial layer, the SGS, receive converging input from both V1 and retinal ganglion cell axons that terminate along the SC surface in a topographic ‘‘visual map’’ of contralateral space (Sperry, 1963; Phillips et al, 2011; Huerta and Harting, 1984b); these retinal axons enter the SC via the SO ventral to the SGS and give rise to activity in superficial SC neurons that encodes the spatial locations of salient visual stimuli
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