Attention to visual, but not tactile, properties of a stimulus results in activation of FOS protein in the visual thalamic reticular nucleus of rats

Previous reports have suggested that the modality-specific sectors of the thalamic reticular nucleus (TRN) may become selectively activated as a result of attention being drawn to their respective sensory modalities. Here we used a task that required the discrimination of digging bowls on the basis of their visual (the colour of the bowl) or tactile (the external texture of the bowl) characteristics. We trained rats to perform both modality discriminations, ensuring the equity of exposure to both visual and tactile aspects of the stimuli. On the test day, animals had to perform only one of the modality discriminations for a 1-h period prior to being transcardially perfused and their brains removed and processed for Fos immunocytochemistry. We found that animals that performed the visual discrimination prior to sacrifice demonstrated a selective activation of cells in the visual TRN. On the other hand, animals that had performed the tactile discrimination, despite encountering the same stimuli and having received equal visual stimulation as the animals performing the visual discrimination, did not have activation of the visual TRN. This evidence suggests that activation of visual TRN is a function of visual selective attention, and not merely visual stimulation. Surprisingly, the same was not true for somatic TRN, which was not labeled in any animals. It is possible that this lack of a double dissociation is the result of modality-specific differences in the attentional demands of the two discrimination tasks.