FIBER PHOTOMETRY OF NEURAL ACTIVITY IN PROJECTION-SPECIFIC SUBPOPULATIONS OF THE ANTERO-MEDIAL (AM) NUCLEUS OF THE THALAMUS

Short-term memory is the ability to hold information for several seconds to guide upcoming actions. In previous studies, we have shown that short-term memory for tactile and auditory stimuli in mice is reflected in the activity of either posterior (sensory) or frontal (premotor) cortical areas during the delay period of sensory discrimination tasks. We found that the cortical area involved depends on the behavioral strategy of the mice (passive vs. active; Gilad et al., 2018; Gallero-Salas et al., 2021). However, we still poorly understand how distributed cortical resources are coordinated to support short-term memory of relevant information and produce appropriate behavior. Based on anatomical evidence, we hypothesize that the anteromedial nucleus (AM) of the anterior thalamus may be a central hub for coordinating delay period activity in sensory vs. premotor cortical areas. Using retrograde dual-color labelling, we identified two segregated subpopulations of AM neurons that project to sensory and premotor areas, respectively. For functional assessment, we obtained calcium recordings of the activity of projection specific AM subpopulations using a cross-sectional viral strategy combined with fiber photometry in mice performing an auditory go/no-go discrimination task. We have obtained first data from AM subpopulations and analyzed how their activity relates to different phases of the task as well as the animal’s behavioral strategy. Together, our work corroborates the notion that AM subpopulations are part of distinct posterior and frontal thalamocortical networks and that AM thus may contribute to the coordination of short-term memory resources distributed in sensory and premotor cortical areas.