Spoken language is produced with a great deal of variability with which listeners must be able to cope. One source of variation is coarticulation, which is due to articulatory planning and transitions between segments. Recently, the temporal features of coarticulation were investigated during a picture/spoken-word matching task by using spliced stimuli carrying either congruent or incongruent subphonemic cues at the CV juncture (Archibald & Joanisse, 2011). ERPs were recorded with attention paid to the phonological mapping negativity (PMN) (Connolly & Phillips, 1994; Newman & Connolly, 2004) – a prelexical response sensitive to violations of phonological expectations. Results found that the PMN varied in response to coarticulation violations and concluded that phonetic features in spoken words influence prelexical processing during word recognition. Using a written-/spoken-word paradigm, Arbour, 2012 controlled phonological shape by using onsets that were either fricatives or stops, hypothesizing that coarticulatory information would be differentially processed due to their temporal differences. Findings supported the PMN’s sensitivity to coarticulation but also showed that temporal and physical differences between onsets modulated the effect. These results raise the question of whether acoustic distance between vowels will modulate prelexical processing of speech as reflected by the PMN amplitude: the focus of the current study. Words were organized into minimal sets such that all onset/coda combinations appeared with each vowel provided that English words resulted. Vowels were one of /i, u, æ, ɑ/, maximizing acoustic distance (height and backness). Data from 20 subjects indicate that the PMN is sensitive to the degree of difference between the original and post-splice vowels. When the number of distinctive features changing is greater, the result is an earlier, more robust PMN. This suggests that the rate of speech recognition is not static but dynamic, and is dependent on likeness of subphonemic features. / Thesis / Master of Science (MSc)

Current models of spoken word recognition have been predominantly based on studies of Indo-European languages. As a result, little is known about the recognition processes involved in the perception of tonal languages (e.g., Mandarin Chinese), and the role of lexical tone in speech perception. One view is that tonal languages are processed phonologically through individual segments, while another view is that they are processed lexically as a whole. Moreover, a recent study claimed to be the first to discover an early phonological processing stage in Mandarin (Huang et al., 2014). There seems to be a lack of investigations concerning tonal languages, as no clear conclusions have been made about the nature of tonal processes, or a model of spoken word recognition that best incorporates lexical tone. The current study addressed these issues by presenting 18 native Mandarin speakers with aural sentences with medial target words, which either matched or mismatched the preceding visually presented sentences with medial target words (e.g, 家 /jia1/ “home”). Violation conditions involved target words that differed in the following ways: tone violation, where only the tone was different (e.g., 价 /jia4/ “price”), onset violation, where only the onset was different (e.g., 虾 /xia1/ “shrimp”), and syllable violation, where both the tone and the onset were different (e.g., 糖 /tang2/ “candy”). We did not find evidence for an early phonological processing stage in Mandarin. Instead, our findings indicate that Mandarin syllables are processed incrementally through phonological segments and that lexical tone is strongly associated with semantic access. These results are discussed with respect to modifications for existing models in spoken word recognition to incorporate the processes involved with tonal language recognition. / Thesis / Master of Science (MSc)

<p>The goal of this study was to elucidate whether articulations of visual-speech are processed phonologically, and in the same manner as auditory-speech. Phonological processing, measured through the amplitude of the Phonological Mapping Negativity (PMN), was compared across three conditions using the electroencephalogram (EEG). Planned polynomial contrasts compared conditions of related and unrelated linguistic stimuli versus a non-linguistic control stimulus. A significant Site x Condition polynomial trend at posterior sites (Pz and Oz) during the N400 tine window revealed that the unrelated condition was most negative in amplitude, an N400-like deflection in the control condition reached similar negative amplitude, while the related condition was the most positive. A significant quadratic trend of PMN amplitude differentiated between the linguistic conditions and the non-linguistic control at site Fz, but did not differentiate the related and unrelated linguistic conditions from each other. These results support a conclusion that non-lexical speech-like and gurning motions of the lips are treated differently than articulations of a meaningful nature. Moreover, the PMN response patterned similarly in the linguistic conditions, compared to the non-linguistic control, indicating phonological processing. The prediction that PMN amplitude will distinguish visual-speech events congruent or incongruent to a phonologically constrained context was not supported.</p> / Master of Science (MSc)

<p><b>Purpose:</b> Children with speech sound disorder (SSD) mispronounce more speech sounds than is typical for their age and a growing body of research suggests that a deficit in speech perception abilities contributes to development of the disorder. However, little work has been done to characterize the neurophysiological processes indexing speech perception deficits in SSD. The primary aim of the current study was to compare the neural activity underlying speech perception in young children with SSD and typical development (TD).</p><p><b>Method</b>: Twenty-eight children ages 4;1-6;0 participated in the current study. Event-related potentials (ERPs) were recorded while children completed a speech perception task which included phonetic (speech sound) and lexical (meaning) matches and mismatches. Groups were compared on their judgment accuracy for matches and mismatches as well as the mean amplitude of the Phonological Mapping Negativity (PMN) and N400 ERP components.</p><p><b>Results</b>: Children with SSD demonstrated lower judgment accuracy across the phonetic and lexical conditions compared to peers with TD. The ERPs elicited by lexical matches and mismatches did not distinguish the groups. However, in the phonetic condition, the SSD group exhibited a more consistent left lateralized PMN effect and a delayed N400 effect over frontal sites compared to the TD group.</p><p><b>Conclusions</b>: These findings provide some of the first evidence of a delay in the neurophysiological processing of phonological information for young children with SSD compared to their peers with TD. This delay was not present for the processing of lexical information, indicating a unique difference between children with SSD and TD related to speech perception of phonetic errors.</p>