Priority Switches in Visual Working Memory are Supported by Frontal Delta and Posterior Alpha Interactions

Abstract

Visual working memory (VWM) distinguishes between representations relevant for imminent versus future perceptual goals. We investigated how the brain sequentially prioritizes visual working memory representations that serve consecutive tasks. Observers remembered two targets for a sequence of two visual search tasks, thus making one target currently relevant, and the other prospectively relevant. We show that during the retention interval prior to the first search, lateralized parieto-occipital EEG alpha (8–14 Hz) suppression is stronger for current compared with prospective search targets. Crucially, between the first and second search task, this difference in posterior alpha lateralization reverses, reflecting the change in priority states of the two target representations. Connectivity analyses indicate that this switch in posterior alpha lateralization is driven by frontal delta/low-theta (2–6 Hz) activity. Moreover, this frontal low-frequency signal also predicts task performance after the switch. We thus obtained evidence for large-scale network interactions underlying the flexible shifting between the priority states of multiple memory representations in VWM.

Hemispheric asymmetries in posterior alpha power reflect the selection and inhibition of spatial context information in working memory

“…We furthermore assessed whether lateral eye movements following memory array and prior to retro-cue presentation had any influence on the difference of alpha power asymmetries between conditions with lateral targets vs. lateral distractors. In line with earlier findings objecting such a relationship (de Vries et al, 2018;Schneider et al, 2019), the ANCOVA with mean contralateral-ipsilateral difference from 560 to 660 ms at F9/10 as covariate still revealed a reliable difference in posterior alpha asymmetry following lateral targets vs. distractors, F(1,22)=28.298, p<0.001, η 2 p=0.563. The interaction of eliciting stimulus and the eye-movement covariate was non-significant, F (1,22)=2.213, p=0.151, η 2 p=0.091.…”

“…As posterior alpha power asymmetries are typically linked to the spatial orienting of attention (Bae & Luck, 2018;Hakim, Adam, Gunseli, Awh, & Vogel, 2019), they should be independent of the number of cued vs. non-cued working memory representations. We further expected to replicate prior findings of an increase in posterior alpha power contralateral to non-cued working memory representations and a respective power decrease contralateral to the position of cued items (de Vries et al, 2018;Schneider et al, 2019). As the neutral retro-cue did not involve the attentional prioritization of either the lateralized or non-lateralized working memory content, it was used for interpreting these effects as selective target enhancement vs. distractor inhibition.…”

“…Oscillatory power in the alpha frequency range (8-13 Hz) increased contralateral to the position of non-cued working memory content when non-lateralized items were indicated as relevant. Furthermore, alpha power decreased contralateral to the position of a cued memory item when the non-cued item was presented above or below fixation (de Vries, van Driel, Karacaoglu, & Olivers, 2018;Schneider, Göddertz, Haase, Hickey, & Wascher, 2019). Importantly, we also manipulated cue meaning by cuing either the to-be-reported targets ('remember cues') or the irrelevant distractors ('forget cues').…”

Current and future goals are represented in opposite patterns in object-selective cortex

“…(B) Trial design for Experiment 2. Here participants were presented with 21 only one object (cow, dresser or skate) as the possible target template for one of two consecutive visual 22 search tasks. Then a retro-cue appeared, when the cue was "1" the memorized object was a current 1 template, for Search 1; cue "2" indicated that the object was a prospective template, for Search 2; 2 finally, when the cue was "0" the memorized item was not a target in either search and thus it was 3 irrelevant in the trial.…”

Flexible working memory through selective gating and attentional tagging

“…Related to this, some models 713 such as LSTM can also gate WM output, in addition to the input. These might come 714 into play in task-switching setups, where multiple goals need to be maintained but only 715 one should drive behavior [99][100][101][102][103][104], and in sequential visual search tasks where multiple 716 items may be held in WM but only one drives attentional selection [95,[105][106][107][108][109][110].…”