The goal of the current research was to provide a novel and comprehensive examination of the connection between rhythm and reading through the combination of multiple experimental stimuli, and to translate the reading aloud research to neurological patients.
Both speech and music perception/production involve sequences of rhythmic events that unfold over time, and the presence of rhythm in both processes has motivated researchers to consider whether musical and speech rhythm engage shared neural regions (Patel, 2008), and whether musical rhythm can influence speech processing (Cason & Schön, 2012). The experimental paradigm involved examining whether reading aloud is affected by the presentation of a rhythmic prime that was either congruent or incongruent with the syllabic stress of the target letter string. The experiments in Chapter 2 used targets that were words that placed the stress on either the first or second syllable (practice vs. police), as well as their corresponding pseudohomophones (praktis vs. poleese), which allowed us to compare lexical and sublexical reading, respectively. In Chapter 3, the experiments involved a paradigm in which target words have stress on the first syllable for nouns, and on the second syllable for verbs. Thus, the design used identical noun-verb word pairs (conflict vs. conflict), as well as their corresponding pseudohomophones (konflikt vs. konflikt). The results from the behavioural experiments demonstrated that naming reaction times were faster for words and pseudohomophones when the rhythmic prime was congruent with the syllabic stress, and slower when the rhythmic prime was incongruent, which suggests that a rhythmic prime matched to the syllabic stress of a letterstring aids reading processes. Functional magnetic resonance imaging (fMRI) was also used in Chapters 2 and 3 to test whether a network involving the putamen is involved in the effect of rhythm on reading aloud. The fMRI results revealed that a network involving the putamen is associated with the effect of congruency between rhythmic stress and syllabic stress on reading aloud, which is consistent with previous literature that has shown this region is involved in reading, rhythm processing, and predicting upcoming events. Chapter 4 was to provide a behavioural and neuroanatomical examination of reading processes in two patients. Case Study 1 examined the effect of rhythmic priming on reading aloud in a patient with Parkinson’s disease (PD), given that these patients exhibit abnormalities in the putamen, which has been associated with rhythm and reading processes. The patient demonstrated the same behavioural effect as normal participants, whereby individuals benefited from the rhythm prime being congruent with the syllabic stress of the target letter string, and the fMRI results revealed that despite disruptions in basal ganglia functioning following PD, there was still activation in the putamen for reading real words. Case Study 2 examined a patient with intractable left temporal lobe epilepsy (TLE) who was undergoing a temporal lobectomy that involved removing regions of the left temporal lobe that are often thought to be important in language processing. The fMRI results showed that all four reading tasks activated the right posterior occipitotemporal region in the ventral visual stream, confirming the right hemisphere dominance in this patient. Together, these findings have implications for developing neurobiological models of reading, translation to localization of function in neurological conditions such as PD and TLE, and may also reveal potential remedial applications for treating speech deficits in patient populations, such as Parkinson’s disease, stuttering, aphasia, and dyslexia
