Cumulative effects of prior knowledge and semantic coherence during speech perception: an fMRI study
2015 (English)Conference paper, Poster (Other academic)
Semantic coherence and prior knowledge enhance perceptual clarity of degraded speech. Recent study by our team has shown that these two effects interact such that the perceptual clarity of noise-vocoded speech (NVS) is still enhanced by semantic coherence when prior knowledge is available from text cues and prior knowledge enhances perceptual clarity of NVS even when semantic coherence is low (Signoret et al., 2015). Here, we investigated the neural correlates of this interaction. We predicted 1) an effect of matching cues for both sentences with high and low semantic coherence in left-lateralized perisylvian areas (Zekveld et al., 2012) and right superior temporal gyrus (Wild et al., 2012), but stronger for low than for high coherent sentences since more resources are required to process sentences with low semantic coherence in the left inferior frontal gyrus (Obleser and Kotz, 2010) and 2) an effect of semantic coherence in temporal and inferior frontal cortex (Lau et al., 2008). The additive effect of semantic coherence when matching cues were provided should be observed in the angular gyrus (Obleser and Kotz, 2010). Twenty participants (age; M=25.14, SD=5.01) listened to sentences and performed an unrelated attentional task during sparse-imaging fMRI. The sentences had high or low semantic coherence, and were either clear, degraded (6-band NV) or unintelligible (1-band NV). Each spoken word was preceded (200 ms) by either a matching cue or a consonant string. Preliminary results revealed significant main effects of Cue (F(1,228) = 21.26; p < .05 FWE) in the left precentral gyrus, the left inferior frontal gyrus and the left middle temporal gyrus confirming the results of Zekveld et al (2012), but neither the main effect of Coherence nor the interaction between Cue and Coherence survived FWE correction. In accordance with our predictions, contrasts revealed a greater effect of matching cues for low than for high coherent sentences (t(19) = 6.25; p < .05 FWE) in the left superior temporal gyrus as well as left inferior frontal gyrus (BA 44 and 45), suggesting greater involvement of both top-down and bottom-up processing mechanisms during integration of prior knowledge with the auditory signal when sentence coherence is lower. There was a marginally greater effect of semantic coherence (t(19) = 3.58; p < .001unc) even when matching cues were provided in the left angular gyrus, the left middle frontal gyrus and the right superior frontal gyrus, suggesting greater involvement of top-down activation of semantic concepts, executive processes and the phonological store during integration of prior knowledge with the auditory signal when the semantic content of the speech is more readily available.
Place, publisher, year, edition, pages
2015. 51-51 p.
IdentifiersURN: urn:nbn:se:liu:diva-123961OAI: oai:DiVA.org:liu-123961DiVA: diva2:894512
The Seventh Annual Meeting of the Society for the Neurobiology of Language, Neurobiology of Language Conference, Chicago, IL, USA, October 15-17, 2015