Poster A27, Tuesday, August 20, 2019, 10:15 am – 12:00 pm, Restaurant Hall
Effects of semantic binding and plausibility on ERPs and oscillatory power in the theta, alpha and beta band
Katrien Segaert1,2, Roksana Markiewicz1, Ali Mazaheri1,2;1School of Psychology, University of Birmingham, 2Centre for Human Brain Health, University of Birmingham
Beyond accessing single-word meaning, language users must compute a representation for the message-level meaning of phrases and sentences. Using EEG, we investigated the neural processes involved in semantic binding and examined both the evoked response (i.e. ERPs: activity phase-locked to the word) and the induced response (i.e. oscillatory activity time-locked but not phase-locked to the word). We compared wordlists for which no binding occurs, to two-word phrases for which semantic binding takes place. We moreover manipulated whether semantic binding was plausible versus implausible. More plausible words might be easier to integrate in a message-level interpretation (e.g. Hagoort, Hald, Bastiaansen & Petersson, 2004), even in a two-word phrase task where the effects of predictability are minimized. We measured the EEG of 29 participants who read two-word phrases. Target words (e.g. monkey, yacht) were presented in 3 conditions: a no binding condition (e.g. mknwkjw monkey, bjkwd yacht), an implausible semantic binding condition (e.g. lavish monkey, elastic yacht) and a plausible semantic binding condition (naughty monkey, sailing yacht). Half of the target words were animate and the other half inanimate. The list of plausible and implausible adjectives was matched for frequency, number of syllables and length. Our results were as follows. There was an N400 effect for target words for which no binding could take place, compared to target words in the semantic binding conditions (p<.05, time interval 0.3 to 0.46 s from the onset of the target word). Target words for which semantic binding takes place (compared to no binding), elicited a smaller theta (4-7Hz) increase (p<.05, time interval 0.5 to 0.8 s from the onset of the target word) and a smaller alpha (8-12Hz) increase (p<.05, time interval 0.95 to 1.15 s from the onset of the target word). There were no significant ERP effects for the plausibility manipulation. However, binding plausible target words elicited less beta (15-20Hz) suppression (p<.05, time interval 0.2 to 0.35 s from the onset of the target word) than binding implausible target words. All statistics were computed using cluster-based permutation tests, which accounted for multiple comparisons (Maris & Oostenveld, 2007). These findings are in line with previous studies linking the N400 and oscillatory power differences in the alpha and beta range to semantic integration, with modulations in function of the ease of integration (e.g. Wang et al. 2012). This suggests that the nature of the binding process is invariant and a minimal paradigm with two-word phrases can be used to study binding. Pushing the complexity down to two-words offers the advantage of isolating the binding process from the contribution of other cognitive processes, such as working memory load. The paradigm might therefore be ideally suited to study the effects of healthy ageing on binding (data collection currently ongoing).
Themes: Meaning: Combinatorial Semantics, Reading
Method: Electrophysiology (MEG/EEG/ECOG)