title: Withholding planned speech is reflected in synchronized beta-band oscillations.
abstract: When engaged in a conversation, speakers sometimes have to withhold a planned response, for example, before it is their turn to speak. In the present study, using magnetoencephalography (MEG) outside of a conversational setting, we investigate the oscillatory brain mechanisms involved in the process of withholding a planned verbal response until it is time to speak. Our participants viewed a sequence of four random consonant strings and one pseudoword, which they had to pronounce when the fifth string (the imperative stimulus) was presented. The pseudoword appeared either as the fourth or fifth stimulus in the sequence, creating two conditions. In the withhold condition, the pseudoword was the fourth string and the verbal response was withheld until the imperative stimulus was presented. In the control condition, the fifth string was the pseudoword, so no response was withheld. We compared oscillatory responses to the withhold relative to the control condition in the time period preceding speech. Alpha-beta power (8-30 Hz) decreased over occipital sensors in the withhold condition relative to the control condition. Source-level analysis indicated a posterior source (i.e., occipital cortex) associated with the alpha-beta power decreases. This occipital alpha-beta desynchronization likely reflects attentional allocation to the upcoming imperative stimulus. Moreover, beta (12-20 Hz) power increased over frontal sensors. Source-level analysis indicated a frontal source (i.e., middle and superior frontal gyri) associated with the beta-power increases. We interpret the frontal beta synchronization to reflect a mechanism aiding the maintenance of the current motor or cognitive state. Our results provide a window into a possible oscillatory mechanism implementing the ability of speakers to withhold a planned verbal response until they have to speak.
authors.affiliation: Donders Institute for Brain, Cognition and Behaviour, Radboud University Nijmegen, Netherlands ; Knight Lab, Department of Psychology and Helen Wills Neuroscience Institute, University of California, Berkeley Berkeley, CA, USA.
authors.forename: Vitória
authors.initials: V
authors.lastname: Piai
authors.affiliation: Donders Institute for Brain, Cognition and Behaviour, Radboud University Nijmegen, Netherlands.
authors.forename: Ardi
authors.initials: A
authors.lastname: Roelofs
authors.affiliation: Department of Psychology and The Beckman Institute for Advanced Science and Technology, University of Illinois Urbana, IL, USA.
authors.forename: Joost
authors.initials: J
authors.lastname: Rommers
authors.affiliation: Independent Researcher Berkeley, CA, USA.
authors.forename: Kristoffer
authors.initials: K
authors.lastname: Dahlslätt
authors.affiliation: Donders Institute for Brain, Cognition and Behaviour, Radboud University Nijmegen, Netherlands.
authors.forename: Eric
authors.initials: E
authors.lastname: Maris
keywords: beta oscillations; conversation; delayed naming; dorsolateral prefrontal cortex; go/no-go; magnetoencephalography; synchronization; turn-taking