INPUT-OUTPUT CIRCUIT MAPPING TO THE HIGHER-ORDER THALAMIC LATERAL COMPLEX OF THE MOUSE

The thalamus, beyond relaying sensory information to the cortex, plays a key role in attention, memory, and cognition. The anterior nuclei of the thalamus (ATN) serve as a central hub of the limbic system, a network long known to be involved in emotion and memory. Over the past two decades, studies have shown that anterodorsal (AD) and laterodorsal (LD) nuclei, both components of ATN, play a key role in the integration of head direction system and visual-landmark information, a computation that ensures the stability of the visuospatial map. In contrast to the AD nucleus, anatomical and functional features of the LD are not well defined. Here, we analyzed the architecture and carried out a brain-wide mapping of the input-output motifs in the mouse laterodorsal (LD) nucleus at micropopulation level using anterograde and retrograde labeling methods. Specifically, we mapped and quantified the sources of cortical and subcortical input to different LD subregions and compared the distribution of their axons. We have demonstrated that LD receives its primary ascending afferents from visual-related structures, including the pretectum, superior colliculus and pregeniculate nucleus. We also found that LD neurons innervate the cingulate, retrosplenial, visual and parahipocampal areas with a specific projection motif. Altogether, these data suggest that subcortical inputs to LD could bring visual-landmark information to the extended hippocampal system and to the retrosplenial cortex, two areas critically involved in the computation of the visuospatial map.