The right ear advantage (REA) phenomenon has been utilized in clinical and research settings to study auditory processing disorders and linguistic lateralization. Previous research has established that the REA is not reliable in its measures within or between individuals. This is likely due to the influence of other variables, such as neuromaturation and attention. One variable that has not been studied in depth in this context is linguistic complexity. It was hypothesized that stimulus conditions with levels of linguistic complexity would elicit corresponding levels of temporal lobe activity. Understanding and controlling the variables that affect the REA will increase the reliability of the measure. Twenty right handed, neurotypical individuals aged 18-29 participated in a functional magnetic resonance imaging (fMRI) study that identified the regions and the extent of activation involved in listening to dichotic syllables, words, and sentences. Three durations of speech babble corresponding to the mean duration of the syllables, words, and sentences were used as control stimuli. Participants listened to dichotic stimuli and reported the stimulus they heard best during an fMRI scan. Reaction time (RT), ear preference, and fMRI data were recorded simultaneously and analyzed post hoc. Behavioral results showed that words had the shortest RTs and the greatest REA; syllables and sentences were similar to each other for both measures. Significant main effects were found in brain regions known to be involved in cognitive control of attention and linguistic processing. Words were associated with significant activation differences for ear preferences and minimal frontal lobe involvement for right ear preference. Syllables caused the least activity in the frontal lobe regions and less voxel activity in the temporal lobes than syllable-length babble. Sentences had the greatest voxel activity in the frontal and temporal lobe regions. It was concluded that words would best reflect the REA in clinical and experimental designs. Words had minimal involvement of frontal lobe regions indicating minimal cognitive control of attention and the largest discrepancies in activation patterns between right and left ear preferences that showed less cognitive power to process right ear stimuli in a dichotic listening situation.
| Identifer | oai:union.ndltd.org:BGMYU2/oai:scholarsarchive.byu.edu:etd-6718 |
| Date | 01 December 2015 |
| Creators | Hyatt, Elizabeth |
| Publisher | BYU ScholarsArchive |
| Source Sets | Brigham Young University |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | Theses and Dissertations |
| Rights | http://lib.byu.edu/about/copyright/ |
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