Separate and overlapping mechanisms of statistical regularities and salience processing in the occipital cortex and dorsal attention network

Abstract

Attention selects behaviorally relevant inputs for in‐depth processing. Beside the role of traditional signals related to goal‐directed and stimulus‐driven control, a debate exists regarding the mechanisms governing the effect of statistical regularities on attentional selection, and how these are integrated with other control signals. Using a visuo‐spatial search task under fMRI, we tested the joint effects of statistical regularities and stimulus‐driven salience. We found that both types of signals modulated occipital activity in a spatially specific manner. Salience acted primarily by reducing the attention bias towards the target location when associated with irrelevant distractors, while statistical regularities reduced this attention bias when the target was presented at a low probability location, particularly at the lower levels of the visual hierarchy. In addition, we found that both statistical regularities and salience activated the dorsal frontoparietal network. Additional exploratory analyses of functional connectivity revealed that only statistical regularities modulated the inter‐regional coupling between the posterior parietal cortex and the occipital cortex. These results show that statistical regularities and salience signals are both spatially represented at the occipital level, but that their integration into attentional processing priorities relies on dissociable brain mechanisms.

Proactive distractor suppression in early visual cortex

“…In line with previous studies our data support that EVC is sensitive to statistical regularities (Adam & Serences, 2021; Beffara et al, 2023; Melloni et al, 2012; Richter et al, 2018; Won et al, 2020; Zhang et al, 2022) highlighting that perception fundamentally relies on (implicit) priors (de Lange et al, 2018). Our results extend previous studies on target learning (Beffara et al, 2023) to distractor suppression, and show that EVC responses were suppressed at the HPDL and nearby neutral locations. Suppression was stimulus-unspecific, resulting in attenuated EVC responses irrespective of the stimulus presented, complementing previous studies (Wang et al, 2019; Zhang et al, 2022).…”

“…Thus, the mere anticipation of search induced by the otherwise uninformative placeholder was sufficient to instantiate neural suppression. This proactive, or predictive, nature of neural suppression guided by implicit prior knowledge aligns well with growing evidence for predictive and anticipatory processes in visual attention (Beffara et al, 2023; Duncan et al, 2023; Serences et al, 2004; Zelinsky & Bisley, 2015). In other words, the brain appears to prepare for potential distractions based on learned probabilities, reflecting a key aspect of predictive processing models.…”

“…Therefore, the visual system is likely to play a role in facilitating distractor suppression using acquired prior knowledge, attenuating neural responses to predictable distractors possibly already at the first stages of the visual cortical hierarchy, in early visual cortex (EVC). Indeed, in line with this proposition, recent fMRI work suggests that statistical regularities during visual search modulate neural processing in EVC (Adam & Serences, 2021;Beffara et al, 2023;Won et al, 2020;Zhang et al, 2022). Specifically, BOLD responses, including in EVC, are enhanced when targets (Beffara et al, 2023) or suppressed when distractors (Zhang et al, 2022) appear at predictable locations.…”

“…Indeed, in line with this proposition, recent fMRI work suggests that statistical regularities during visual search modulate neural processing in EVC (Adam & Serences, 2021;Beffara et al, 2023;Won et al, 2020;Zhang et al, 2022). Specifically, BOLD responses, including in EVC, are enhanced when targets (Beffara et al, 2023) or suppressed when distractors (Zhang et al, 2022) appear at predictable locations. Together these findings are consistent with the notion of spatial priority maps, reflecting prior knowledge, facilitating visual search by both target enhancement and distractor suppression (Awh et al, 2012;Fecteau & Munoz, 2006;Itti & Koch, 2000;Serences & Yantis, 2006;Theeuwes et al, 2022).…”

“…Combined, these findings may suggest that later processing stages in higher visual areas and downstream from visual cortex refine the initial neural suppression in EVC to facilitate task performance in a more nuanced fashion. It is plausible that areas in parietal and frontal cortex, including the dorsal attention network (Beffara et al, 2023; Zhang et al, 2022), contribute to this refinement. An open question is whether the broad suppression shown here reflects limitations of the neural mechanisms underlying distractor suppression in EVC, such as less spatially specific feedback, or a neural efficiency trade-off, in which a more accurate suppression is not sufficiently beneficial to warrant the required metabolic demand of more precise modulations in EVC.…”