The layer 6b theory of attention.

Could a long-overlooked cortical layer hold the key to attention? Essential for our perception and everyday experience, attention is thought to depend on precisely controlled feedback loops between cortical layer 5 and the higher-order thalamus. However, despite their critical importance, the circuits that precisely control these "attention loops" remain poorly understood. Interestingly, recent advances revealed that the deepest cortical neurons, layer 6b (L6b), may be a powerful yet previously unrecognized conductor of these feedback loops. L6b is positioned at the intersection of top-down cortical drive and convergent neuromodulation and its projections appear uniquely equipped to precisely control these loops. Here, we propose the L6b attention theory (LAT), a circuit-based model that complements and extends existing theories of attention. LAT suggests that this overlooked layer is a missing link in our understanding of attention and cognition, offering new insights into neuropsychiatric disorders and how we understand our mental state.