Statistical learning re-shapes the center-surround inhibition of the visuo-spatial attentional focus.

To effectively navigate a crowded and dynamic visual world, our neurocognitive system possesses the remarkable ability to extract and learn its statistical regularities to implicitly guide the allocation of spatial attention resources in the immediate future. The way through which we deploy attention in the visual space has been consistently outlined by a "center-surround inhibition" pattern, wherein a ring of sustained inhibition is projected around the center of the attentional focus to optimize the signal-noise ratio between goal-relevant targets and interfering distractors. While it has been observed that experience-dependent mechanisms could disrupt the inhibitory ring, whether statistical learning of spatial contingencies has an effect on such a surround inhibition and - if any - through which exact mechanisms it unravels are hitherto unexplored questions. Therefore, in a visual search psychophysical experiment, we aimed to fill this gap by entirely mapping the visuo-spatial attentional profile, asking subjects (N = 26) to detect and report the gap orientation of a 'C' letter appearing either as a color singleton (Baseline Condition) or as a non-salient probe (Probe Condition) - among other irrelevant objects - at progressively increasing probe-to-singleton distances. Critically, we manipulated the color singleton spatial contingency so as to make it appear more frequently adjacent to the probe, specifically at a spatial distance where attending the color singleton generates surround-inhibition on the probe, hindering attentional performance. Results showed that statistical learning markedly reshaped the attentional focus, transforming the center-surround inhibition profile into a non-linear gradient one through a performance gain over the high probability probe-to-singleton distance. Noteworthy, such reshaping was uneven in time and asymmetric, as it varied across blocks and specifically appeared only within manipulated visual quadrants, leaving unaltered the unmanipulated ones. Our findings offer insights of theoretical interest in understanding how environmental regularities orchestrate the way we allocate attention in space through plastic re-weighting of spatial priority maps. Additionally, going beyond the physical dimension, our data provide interesting implications about how visual information is coded within working memory representations, especially under scenarios of heightened uncertainty.