Past work has demonstrated that active suppression of salient distractors is a critical part of visual selection. Evidence for goaldriven suppression includes below-baseline visual encoding at the position of salient distractors (Gaspelin and Luck, 2018) and neural signals such as the distractor positivity (Pd) that track how many distractors are presented in a given hemifield (Feldmann-Wüstefeld and Vogel, 2019). One basic question regarding distractor suppression is whether it is inherently spatial or nonspatial in character. Indeed, past work has shown that distractors evoke both spatial (Theeuwes, 1992) and nonspatial forms of interference (Folk and Remington, 1998), motivating a direct examination of whether space is integral to goal-driven distractor suppression. Here, we use behavioral and EEG data from adult humans (male and female) to provide clear evidence for a spatial gradient of suppression surrounding salient singleton distractors. Replicating past work, both reaction time and neural indices of target selection improved monotonically as the distance between target and distractor increased. Importantly, these target selection effects were paralleled by a monotonic decline in the amplitude of the Pd, an electrophysiological index of distractor suppression. Moreover, multivariate analyses revealed spatially selective activity in the h-band that tracked the position of the target and, critically, revealed suppressed activity at spatial channels centered on distractor positions. Thus, goal-driven selection of relevant over irrelevant information benefits from a spatial gradient of suppression surrounding salient distractors.

Ideally, both enhancement of relevant and suppression of irrelevant information contribute to the deployment of visual selective attention. When stimuli are sufficiently salient, however, they can capture attention automatically before they are suppressed and thus interfere with the selection relevant stimuli. Here we analyzed how much interference is induced by distractors of varying distance to a target stimulus and how the visual system responds to that interference. We used an additional singleton visual search task in which participants had to search for a target and ignore a salient distractor presented at different distances to the target. We found behavioral evidence for spatial filtering costs: distractor interference increased with distractor proximity to the target, distractor interference was reduced when the target and distractor spatially coincided, and responses were slowed down when distractor and target were incompatible. Event-related potentials of the EEG paralleled this pattern: N2pc amplitude (reflecting target enhancement) increased while Pd amplitude (reflecting distractor suppression) decreased as the distance increased between target and distractor. This suggests less efficient enhancement of relevant and more effortful suppression of irrelevant information when target and singleton are closer, in line with the idea of increased neural competition for stimuli within the same receptive field. Distractors elicited an N2pc that was not affected by target-distractor distance, suggesting that varying attentional capture does not contribute to filtering costs. Importantly, when the distractor was presented in the same position as the target, we observed robust interference relative to a no-distractor condition. This evidence against a pure-capture account and suggests nonspatial interference contributes to the overall increased processing time when salient stimuli are presented. We additionally applied an inverted encoding model to track attentional subprocesses in a more fine-grained manner. Alpha-band topography tracked sustained top-down attention deployment towards targets, and transient but more pronounced attentional capture by the distractor. Below-baseline channel activity for distractors in the theta-band topography of the EEG signal tracked spatial suppression. In sum, our results show that salient distractors induce both spatial and nonspatial interference and that the visual system responds with a gradient of suppression that can account for distance-variant processing costs.

Cholinergic interneurons (ChIs) of the nucleus accumbens (NAc) are important for mediating the behavioral response to rewarding stimuli. A major role for these cells is to regulate dopamine (DA) transmission by activating cholinergic receptors at local DAergic nerve terminals. However, the mechanisms that enable cholinergic neurons to enhance DA release in response to reward remain unknown. Here we report that the hyperpolarization-activated cyclic nucleotide-gated channel 2 (HCN2) in NAc ChIs mediates an enhancement in DA signaling in response to rewarding stimuli. The HCN current in NAc ChIs and its modulation by DA, as well as the increase in cholinergic efflux by local cocaine infusion were impaired in mice with deletion of HCN2 in cholinergic cells. Enhancement in the DA efflux and signaling in the NAc in response to rewarding stimuli, as well as cocaine conditioning were also dependent on HCN2 in ChIs. These results provide a mechanistic link between the activity of NAc ChIs and reward encoding.

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