Meaningful semantic context has been shown to improve comprehension of spoken sentences by young and old adults, especially in difficult listening conditions. Whether older adults benefit differently than younger adults is a topic of some controversy. I asked young (14 participants, 18-25) and older adults (20 participants, 60-75) to report entire sentences which contained either a coherent or anomalous global semantic context (e.g. coherent: “Her new skirt was made of denim”, anomalous: “Her good slope was done in carrot”). Sentences were mixed with signal-correlated noise, at 10 signal-to-noise ratios (-6 to +2 dB and clear speech). Percentage scores were converted to rationalized arcsine units and subjected to a repeated-measures ANOVA; slopes from psychometric functions fitted to the transformed data were also analyzed. Cognitive and hearing threshold differences were considered as factors influencing results. Finally, individual variability in the use of context was explored. Comprehension by both groups benefited from meaningful context, without a clear difference in the overall amount of benefit obtained. Cognitive factors did not appear to influence the results, although differences in hearing thresholds likely contributed to the consistent performance decrement for older adults. Individuals varied greatly in their use of context, a possible explanation for inconsistent results in studies comparing context use by young and older people.
fMRI was then used to look at neural activity associated with deriving benefit from meaningful context. Whole-brain EPI data were acquired from young (16 participants, 19-26) adults using a sparse imaging design. Participants heard coherent and anomalous sentences in the scanner, and were asked to report what they heard on half of the trials. Individual’s word-report data obtained in the scanner were used to model intelligibility in the analysis and results were compared to an analysis conducted using intelligibility estimates based on group data from another study. In addition to bilateral temporal activity associated with increasing intelligibility, I observe a large left inferior-frontal region in which BOLD signal correlated more strongly with highly intelligible anomalous compared to highly intelligible coherent prose, presumably reflecting challenged semantic integration and supporting Hagoort’s (2005) model of semantic unification. / Thesis (Master, Neuroscience Studies) -- Queen's University, 2008-09-18 23:01:40.979
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:OKQ.1974/1450 |
| Date | 19 September 2008 |
| Creators | MacDonald, Heather |
| Contributors | Queen's University (Kingston, Ont.). Theses (Queen's University (Kingston, Ont.)) |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English, English |
| Detected Language | English |
| Type | Thesis |
| Format | 830268 bytes, application/pdf |
| Rights | This publication is made available by the authority of the copyright owner solely for the purpose of private study and research and may not be copied or reproduced except as permitted by the copyright laws without written authority from the copyright owner. |
| Relation | Canadian theses |
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