Sensory Prioritization in Rats: Behavioral Performance and Neuronal Correlates.

Operating with some finite quantity of processing resources, an animal would benefit from prioritizing the sensory modality expected to provide key information in a particular context. The present study investigated whether rats dedicate attentional resources to the sensory modality in which a near-threshold event is more likely to occur. We manipulated attention by controlling the likelihood with which a stimulus was presented from one of two modalities. In a whisker session, 80% of trials contained a brief vibration stimulus applied to whiskers and the remaining 20% of trials contained a brief change of luminance. These likelihoods were reversed in a visual session. When a stimulus was presented in the high-likelihood context, detection performance increased and was faster compared with the same stimulus presented in the low-likelihood context. Sensory prioritization was also reflected in neuronal activity in the vibrissal area of primary somatosensory cortex: single units responded differentially to the whisker vibration stimulus when presented with higher probability compared with lower probability. Neuronal activity in the vibrissal cortex displayed signatures of multiplicative gain control and enhanced response to vibration stimuli during the whisker session. In conclusion, rats allocate priority to the more likely stimulus modality and the primary sensory cortex may participate in the redistribution of resources. SIGNIFICANCE STATEMENT: Detection of low-amplitude events is critical to survival; for example, to warn prey of predators. To formulate a response, decision-making systems must extract minute neuronal signals from the sensory modality that provides key information. Here, we identify the behavioral and neuronal correlates of sensory prioritization in rats. Rats were trained to detect whisker vibrations or visual flickers. Stimuli were embedded in two contexts in which either visual or whisker modality was more likely to occur. When a stimulus was presented in the high-likelihood context, detection was faster and more reliable. Neuronal recording from the vibrissal cortex revealed enhanced representation of vibrations in the prioritized context. These results establish the rat as an alternative model organism to primates for studying attention.