Poster D62, Wednesday, August 21, 2019, 5:15 – 7:00 pm, Restaurant Hall
Alpha Band ERD Associated with the Increased Use of Formulaic Language in a Naturalistic Production Task
Seana Coulson1,2, Claudio Hartmann1, Jared Gordon1, Jacob Momsen1,2;1University of California San Diego, 2San Diego State University
Here we examine event related spectral perturbations (ERSP) associated with the emergence and use of formulaic language in a demanding speech production task. In this task, participants viewed videos of actors performing simple actions and were asked to verbally describe the clips as a sportscaster might do. Actions included standing up, sitting down, picking up a box, putting down a box, jumping, and walking, performed by a variety of different actors in six different manners. Although all videos were unique, we hypothesized that the structured nature of this video corpus would induce participants to make increasing use of speech formulas, that is, sequences of words or structures including slots for variable content. In view of previous evidence that the retrieval of well-integrated semantic information is associated with event-related desynchronization (ERD) in the alpha band of the electroencephalogram (EEG), we hypothesized that the use of speech formulas (retrieved and produced as integrated units) would be indexed by changes in the amplitude of induced alpha-band activity. Participants were 12 adults, 18-30 years of age, who were fluent English speakers, and had no history of neurological or psychiatric disorders. As the study was designed to capture qualitative changes in speech over time and the corresponding shifts in participants’ ERSPs, we continuously recorded participants’ speech and EEG as they described the action in a total of 200 videos, divided into four blocks of 50 clips apiece. Two seconds after the onset of each clip, a tone sounded to signal participants to begin their narration, and the appearance of a fixation cross after the offset of the video signaled participants to stop. Linear mixed effects models suggested the number of words per utterance (video clip) increased as a function of Block (F=11.25, p<0.0001), with coefficient of 0.7 for the second block, 1.5 for the third block, and 1.8 for the final block. However, linguistic diversity, expressed as the percentage of unique words used by each participant went down overall (Block F=13.63, p<0.0001), with significantly negative coefficients emerging only in the third (-1.78) and fourth (-2.6) blocks. Behavioral data are thus consistent with our prediction that experience with the task would lead participants to increasingly utilize speech formulas. Oscillatory brain activity was examined by extracting EEG from 500ms before the onset of the beep that prompted speech production (the baseline interval) until 3 seconds afterwards. Artifactual activity due to eye movements and overt speech production was minimized via adaptive mixture ICA and blind source separation with cross-correlation analysis (BSSCCA), and remaining noisy trials were rejected by hand. Alpha band activity was measured between 7-11Hz during the time period 700-1200ms for analysis with linear mixed effects models. Relative to the pre-stimulus baseline, all measurements were negative, indicating ERD. Alpha band activity differed significantly as a function of Block (p<0.001), with a positive coefficient for the second block (0.2), and negative coefficients in the third (-0.30), and fourth (-0.38) blocks. Greater alpha band ERD during speech production thus paralleled the decrease in linguistic diversity due to formulaic language.
Themes: Language Production, Control, Selection, and Executive Processes
Method: Electrophysiology (MEG/EEG/ECOG)