Dr. Anna Schroeder, a leading neuroscientist, graces our show in this episode to shed light on a crucial yet understudied facet of neocortical circuits. Top-down projections in our brain act as a bridge between previous experiences, current objectives, and the sensory neocortex, playing a pivotal role in our perception and memory. While excitatory pathways have been typically associated with top-down control, inhibitory top-down projections remain a largely uncharted territory.

Dr. Schroeder's ground-breaking research, employing a unique blend of synaptic two-photon calcium imaging, circuit mapping, cortex-dependent learning, and chemogenetics in mice, uncovers the GABAergic afferents from the subthalamic zona incerta as a significant source of top-down input to the neocortex. The zona incerta's inhibitory projections are critical for learning, as they transmit integrated top-down information that is essential for encoding sensory stimuli.

Perhaps the most striking revelation from Dr. Schroeder's research is the bidirectional encoding of learned top-down relevance by the incertocortical afferents, which stands out from traditional excitatory pathways. These afferents form a disinhibitory circuit, and it is the swift appearance of negative responses that primarily drives changes in stimulus representation.

Through her findings, Dr. Schroeder provides a compelling perspective on the unique contribution of long-range (dis)inhibitory afferents to the computational flexibility of neocortical circuits.

Dr. Anna Schroeder, Neocortical Circuits, GABAergic Afferents, Zona Incerta, Top-Down Projections, Sensory Neocortex, Two-Photon Calcium Imaging, Circuit Mapping, Cortex-Dependent Learning, Chemogenetics, Disinhibitory Circuit.

Inhibitory top-down projections from zona incerta mediate neocortical memory https://doi.org/10.1016/j.neuron.2022.12.010