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

Abstract

Retroactive cuing of information after encoding improves working memory performance.However, there is an ongoing debate on the contribution of target enhancement vs. distractor inhibition attentional sub-processes to this behavioral benefit. We investigated the electrophysiological correlates of retroactive attentional orienting by means of oscillatory EEG parameters. In order to disentangle excitatory and inhibitory attentional processes, the to-bememorized information was presented in a way that posterior hemispheric asymmetries in oscillatory power could be unambiguously linked to lateral target vs. distractor processing.Alpha power (8-13 Hz) asymmetries were insensitive to the number of cued or non-cued items, supporting their relation to the spatial orienting of attention. Furthermore, we found an increase in posterior alpha power contralateral to the position of non-cued working memory content that differed reliably from the alpha asymmetry in a neutral control condition. This correlate of an inhibitory sub-process of the spatial orienting of attention following the retroactive cues was further related to the participants' ability to control for the impact of irrelevant information on working memory retrieval. These findings indicate that shifting the spatial focus of attention within working memory makes use of an inhibitory attentional mechanism for guaranteeing a target-oriented retrieval process.

A dual mechanism underlying retroactive shifts of auditory spatial attention: dissociating target- and distractor-related modulations of alpha lateralization

“…Thus, it remains possible that distractor inhibition is an automatic consequence of target prioritization. Further, if we do conceptualize distractor inhibition as a top-down control mechanism that deteriorates the respective representations 36 , the question brought forth above likewise applies: If non-cued items are inhibited, why do non-cued items still cause interference when presented as a probe stimulus? Accordingly, both behavioral as well as neural evidence question the notion that an (active) inhibition mechanism completely deteriorates the non-cued item: On a behavioral level, using a series of cues, it has been shown that originally cued and then defocused items remain strengthened and result in faster and more accurate performance compared to trials in which a previously un-cued item (and thus “un-strengthened” item) is probed 11 .…”

A dual mechanism underlying retroactive shifts of auditory spatial attention: dissociating target- and distractor-related modulations of alpha lateralization

“…Yet, the exact nature of such an inhibitory attentional signature still remains elusive. That is, if we conceptualize distractor inhibition as a top-down control mechanism that deteriorates the respective representations 34 , the question brought forth above likewise applies (cf. 3.1): If non-cued items are actively inhibited, why do non-cued items still cause interference when presented as a probe stimulus?…”