Sensory systems transform extrinsic sensory impulses into internal representations which individuals use to make decisions and act. Regardless of modality, sensory internalization is fundamentally integrative, applying both feedforward and feedback architectures to link disparate systems together. Here, we will use trans-regional, population-scale recordings with Neuropixels probes and 2P calcium imaging (Section 8b) to identify the algorithms by which sensory inputs are transformed during internalisation. We will cover the spectrum from pure to integrated sensory modalities, and from low- to high-end cortices, by investigating a range of pathways and functions including (WP2A:) the feedforward assimilation of olfactory input into high-end cortices, (WP2B:) the integration of visual and tactile signals underlying object recognition, and (WP2C:) the calibration of visual processing against motor feedback. We will determine whether these functions emerge from specific computational processes, such as attractor or sequence dynamics (P1,P2), how they are coordinated over anatomically extended circuits (P4), and how they change during learning (P3). Ultimately, we will assess whether algorithms are shared or diverge across functions and pathways.