Dissociable Neural Mechanisms Underlie the Effects of Attention on Visual Appearance and Response Bias

Conflicting Sensory Information Sharpens the Neural Representations of Early Selective Visuospatial Attention

Adaptive behaviors require the ability to resolve conflicting information caused by the processing of incompatible sensory inputs. Prominent theories of attention have posited that early selective attention helps mitigate cognitive interference caused by conflicting sensory information by facilitating the processing of task-relevant sensory inputs and filtering out behaviorally irrelevant information. Surprisingly, many recent studies that investigated the role of early selective attention on conflict mitigation have failed to provide positive evidence. Here, we examined changes in the selectivity of early visuospatial attention in male and female human subjects performing an attention-cueing Eriksen flanker task, where they discriminated the shape of a visual target surrounded by congruent or incongruent distractors. We used the inverted encoding model to reconstruct spatial representations of visual selective attention from the topographical patterns of amplitude modulations in alpha band oscillations in scalp EEG (∼8-12 Hz). We found that the fidelity of the alpha-based spatial reconstruction was significantly higher in the incongruent compared with the congruent condition. Importantly, these conflict-related modulations in the reconstruction fidelity occurred at a much earlier time window than those of the lateralized posterior event-related potentials associated with target selection and distractor suppression processes, as well as conflict-related modulations in the frontocentral negative-going wave and midline-frontal theta oscillations (∼3-7 Hz), thought to track executive control functions. Taken together, our data suggest that conflict resolution is supported by the cascade of neural processes underlying early selective visuospatial attention and frontal executive functions that unfold over time.

Endogenous attention enhances contrast appearance regardless of stimulus contrast

There has been enduring debate on how attention alters contrast appearance. Recent research indicates that exogenous attention enhances contrast appearance for low-contrast stimuli but attenuates it for high-contrast stimuli. Similarly, one study has demonstrated that endogenous attention heightens perceived contrast for low-contrast stimuli, yet none have explored its impact on high-contrast stimuli. In this study, we investigated how endogenous attention alters contrast appearance, with a specific focus on high-contrast stimuli. In Experiment 1, we utilized the rapid serial visual presentation (RSVP) paradigm to direct endogenous attention, revealing that contrast appearance was enhanced for both low- and high-contrast stimuli. To eliminate potential influences from the confined attention field in the RSVP paradigm, Experiment 2 adopted the letter identification paradigm, deploying attention across a broader visual field. Results consistently indicated that endogenous attention increased perceived contrast for high-contrast stimuli. Experiment 3 employed equiluminant chromatic letters as stimuli in the letter identification task to eliminate potential interference from contrast adaption, which might have occurred in Experiment 2. Remarkably, the boosting effect of endogenous attention persisted. Combining the results from these experiments, we propose that endogenous attention consistently enhances contrast appearance, irrespective of stimulus contrast levels. This stands in contrast to the effects of exogenous attention, suggesting that mechanisms through which endogenous attention alters contrast appearance may differ from those of exogenous attention.

Sustained attention operates via dissociable neural mechanisms across different eccentric locations

In primates, foveal and peripheral vision have distinct neural architectures and functions. However, it has been debated if selective attention operates via the same or different neural mechanisms across eccentricities. We tested these alternative accounts by examining the effects of selective attention on the steady-state visually evoked potential (SSVEP) and the fronto-parietal signal measured via EEG from human subjects performing a sustained visuospatial attention task. With a negligible level of eye movements, both SSVEP and SND exhibited the heterogeneous patterns of attentional modulations across eccentricities. Specifically, the attentional modulations of these signals peaked at the parafoveal locations and such modulations wore off as visual stimuli appeared closer to the fovea or further away towards the periphery. However, with a relatively higher level of eye movements, the heterogeneous patterns of attentional modulations of these neural signals were less robust. These data demonstrate that the top-down influence of covert visuospatial attention on early sensory processing in human cortex depends on eccentricity and the level of saccadic responses. Taken together, the results suggest that sustained visuospatial attention operates differently across different eccentric locations, providing new understanding of how attention augments sensory representations regardless of where the attended stimulus appears.

We know what attention is!

Attention is one of the most thoroughly investigated psychological phenomena, yet skepticism about attention is widespread: we do not know what it is, it is too many things, there is no such thing. The deficiencies highlighted are not about experimental work but the adequacy of the scientific theory of attention. Combining common scientific claims about attention into a single theory leads to internal inconsistency. This paper demonstrates that a specific functional conception of attention is incorporated into the tasks used in standard experimental paradigms. In accepting these paradigms as valid probes of attention, we commit to this common conception. The conception unifies work at multiple levels of analysis into a coherent scientific explanation of attention. Thus, we all know what attention is.