Shin, H., Ogando, M. B., et al. (2025).
Nature Neuroscience.
Abstract
When sensory information is incomplete, the brain relies on prior expectations to infer perceptual objects. Despite the centrality of this process to perception, the neural mechanisms of sensory inference are not understood. Here we used illusory contours (ICs), multi-Neuropixels measurements, mesoscale two-photon (2p) calcium imaging and 2p holographic optogenetics in mice to reveal the neural codes and circuits of sensory inference. We discovered a specialized subset of neurons in primary visual cortex (V1) that respond emergently to illusory bars but not to component image segments. Selective holographic photoactivation of these ‘IC-encoders’ recreated the visual representation of ICs in V1 in the absence of any visual stimulus. These data imply that neurons that encode sensory inference are specialized for receiving and locally broadcasting top-down information. More generally, pattern completion circuits in lower cortical areas may selectively reinforce activity patterns that match prior expectations, constituting an integral step in perceptual inference.
Here are some thoughts:
This study reveals the neural circuit mechanism for perceptual "filling-in," demonstrating that the primary visual cortex (V1) plays an active, constructive role in sensory inference. The researchers identified a specialized subset of neurons in V1 that respond selectively to illusory contours. Crucially, they found that these neurons do not merely receive top-down predictions but actively broadcast this inferred signal locally through recurrent connections, a process termed "pattern completion." Using optogenetics, they showed that artificially activating these neurons alone was sufficient to recreate the brain's representation of an illusory contour in the absence of any visual stimulus.
Also important: This process is driven by the brain's need for survival and efficiency, as it constantly uses prior expectations—formed from experience—to quickly interpret an often-ambiguous world. This provides a fundamental biological basis for top-down influences on perception, showing how the brain embeds these expectations and Gestalt-like inferences at the earliest stages of cortical processing.
This research can be interpreted that life is a projective test, even at a biological level. We are not simply reacting to an objective world; we are constantly interpreting an incomplete and noisy signal through the lens of our brain's built-in and learned expectations. This study shows that this projective process is not a high-level cognitive feature but is built into the very fabric of our perceptual machinery.
