Comment: How expectation modulates attentional enhancement and inhibition

People receive a large amount of external information every day, and selective attention allows them to prioritize the processing of important information given their limited perceptual capacity. Generally speaking, selective attention can enhance the processing of target stimuli and suppress non-target stimuli. However, people's expectations about information can influence these two regulatory processes.

However, the mechanisms by which expectations affect selective enhancement and suppression are not the same. The effect of expectations on enhancement occurs early, and can even enhance the representation of target stimuli before they appear, which is an active form of regulation. Researchers generally agree on this. However, there is much controversy over the processing mechanisms of expected suppression. The mainstream view is that expected suppression is mainly modulated by resonance in the alpha frequency band (8-12 Hz) before the stimulus appears, which is an active form of regulation. However, there are also two non-active forms of suppression: one is secondary suppression, which is the non-target suppression caused by target enhancement; the other is expected encoding suppression, which is a direct regulation of non-target stimuli by expectations. Therefore, further research is needed on how expectations regulate the suppression of irrelevant information.

In order to better understand the research progress in this field, we reviewed van Moorselaar et al. (2019) published in the Journal of Neuroscience. Their study used a learning and spatial search task, combined with different EEG analysis methods, to explore the mechanisms of expected enhancement and suppression. The results showed that subjects were able to improve their performance by effectively anticipating the spatial location of target and interfering stimuli through learning. The authors ruled out active and secondary suppression explanations by manipulating experimental variables, and attributed the behavioral enhancement brought about by expectations to expected encoding suppression. The study concludes that there are significant differences between attentional enhancement and suppression regulated by expectations.

Our review first affirms the importance of this study, and then points out that the specificity of enhancement and suppression processing can better explain some phenomena found by previous researchers in conflict processing (e.g., Egner et al., 2005, which only found target enhancement but not non-target suppression). At the same time, we also points out some shortcomings of this study, including the inability to reflect the progressive influence of learning on selective processing, such as how active suppression is transformed into expected encoding suppression before and after expectations are formed. It also proposes some key scientific questions that can be explored in the future, such as how expected enhancement and suppression work together to enhance target-oriented behavior, whether there are similar mechanisms in cross-channel contexts, and whether learned enhancement and suppression can be transferred.

Citation: Li, Z., Goschl, F., & Yang, G. (2020). Dissociated Neural Mechanisms of Target and Distractor Processing Facilitated by Expectations. Journal of Neuroscience (Journal Club), 40(10), 1997-1999. DOI: https://doi.org/10.1523/JNEUROSCI.2562-19.2020


Reference:

van Moorselaar D, Slagter HA (2019) Learning what is irrelevant or relevant: expectations facilitate distractor inhibition and target facilitation through distinct neural mechanisms. J Neurosci 39:6953–6967.

Egner, T., & Hirsch, J. (2005). Cognitive control mechanisms resolve conflict through cortical amplification of task-relevant information. Nature Neuroscience, 8(12), 1784-1790. https://doi.org/10.1038/nn1594 

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