Redding, Z. V. | Search bioRxiv

bioRxiv2023

Distractor suppression does and does not depend on pre-distractor alpha-band activity

Selective attention enhances behaviorally important information and suppresses distracting information. Research on the neural basis of selective attention has largely focused on sensory enhancement, with less focus on sensory suppression. Enhancement and suppression can operate through a push-pull relationship that arises from competitive interactions among neural populations. There has been considerable debate, however, regarding (i) whether suppression can also operate independent of enhancement and (ii) whether neural processes associated with the voluntary deployment of suppression can occur prior to distractor onset. We provide further behavioral and electrophysiological evidence of independent suppression at cued distractor locations while humans performed a visual search task. We specifically utilize two established EEG markers of suppression: alpha power ([~]8-15 Hz) and the distractor positivity (PD). Increased alpha power has been linked with attenuated sensory processing, while the PD--a component of event-related potentials--has been linked with successful distractor suppression. The present results demonstrate that cueing the location of an upcoming distractor speeded responding and led to an earlier onset PD, consistent with earlier suppression due to strategic use of a spatial cue. We further demonstrate that higher pre-distractor alpha power contralateral to distractors was generally associated with successful suppression on both cued and non-cued trials. However, there was no consistent change in alpha power associated with the spatial cue, meaning cueing effects on behavioral and neural measures occurred independent of alpha-related gating of sensory processing. These findings reveal the importance of pre-distractor neural processes for subsequent distractor suppression. Significance StatementSelective suppression of distracting information is important for survival, contributing to preferential processing of behaviorally important information. Does foreknowledge of an upcoming distractors location help with suppression? Here, we recorded EEG while subjects performed a target detection task with cues that indicated the location of upcoming distractors. Behavioral and electrophysiological results revealed that foreknowledge of a distractors location speeded suppression, thereby facilitating target detection. The results further revealed a significant relationship between pre-stimulus alpha-band activity and successful suppression; however, pre-stimulus alpha-band activity was not consistently lateralized relative to the spatially informative cues. The present findings therefore demonstrate that target detection can benefit from foreknowledge of distractor location in a process that is independent of alpha-related gating of sensory processing.

neuroscience↗

bioRxiv2022

Rhythmic temporal coordination of neural activity avoids representational conflict during working memory

Selective attention1 is characterized by alternating states associated with either attentional sampling or attentional shifting, helping to avoid functional conflicts by isolating function-specific neural activity in time2-5. We hypothesized that such rhythmic temporal coordination might also help to avoid representational conflicts during working memory6. Multiple items can be simultaneously held in working memory, and these items can be represented by overlapping neural populations7-9. Traditional theories propose that short-term storage of to-be-remembered items occurs through persistent neural activity10-12, but when neurons are simultaneously representing multiple items, persistent activity creates a potential for representational conflicts. In comparison, more recent, activity-silent theories of working memory propose that synaptic changes also contribute to the short-term storage of to-be-remembered items13-16. Transient bursts in neural activity17, rather than persistent activity, could serve to occasionally refresh these synaptic changes. Here, we used EEG and response times (RTs) to test whether rhythmic temporal coordination helps to isolate neural activity associated with different to-be-remembered items, which would help to avoid representational conflicts. Consistent with this hypothesis, we report that the relative strength of different item representations alternates over time as a function of frequency-specific phase. Although RTs were linked to theta (~6Hz) and beta (~25 Hz) phase during a memory delay, the relative strength of item representations only alternated as a function of beta phase. The present findings (i) are consistent with rhythmic temporal coordination being a general mechanism for avoiding either functional or representational conflicts during cognitive processes, and (ii) inform models describing the role of oscillatory dynamics in organizing working memory13,18-21.

neuroscience↗