Final Report Summary - CORTIC_AL_GORITHMS (Cortical algorithms for perceptual grouping)
The project Cortic_al_gorithms focused on a simple and elementary question: “Why do we perceive objects and not individual features?” Visual perception starts with localized filters that subdivide the image into fragments that undergo separate analyses. The ERC funded research investigated how our visual system reconstructs the objects that surround us. The prevailing view has been that perceptual grouping is achieved by a parallel, pre-attentive process. In contrast, the research program demonstrated that the visual cortex also implements a serial, attention-demanding algorithm for perceptual grouping. We measured the reaction times of human observers in tasks probing perceptual organization, and recorded neuronal activity in the visual and frontal cortex of macaque monkeys and mice during perceptual grouping tasks. The results demonstrate that perceptual grouping relies on two complementary processes, “base-grouping” and “incremental grouping”. Base-grouping is pre-attentive and relies on feed-forward connections from lower to higher areas that activate neurons and determine their stimulus selectivity. In contrast, incremental grouping relies on an attention demanding process that is implemented by the recirculation of neuronal activity through feedback and horizontal connections, which link the distributed neurons that represent all features that belong to the same perceptual object, even if they are located in different brain regions. The ERC-funded proposal thereby provided deep insight into the algorithms for perceptual grouping as they are implemented in our brains.