Experimental methods to study atypical language development

In this chapter we present current issues on experimental methods in the study of atypical language development with a focus on developmental language disorders (DLD). We first present a short history of terminology surrounding DLD and follow this with a discussion of critical topics related to DLD assessment including cross-linguistic research, multilingualism, persisting disorders in teenagers, age-differences (pre-school, school age, adolescence, and adults) in manifestations and domains studied, language comprehension versus production, and cognitive assessment. We also bring focus to the question of matching control groups in the study of atypical language development. We present the most common methods used in the investigation of language impairments from the behavioural and neurocognitive perspectives. We provide an overview of the issues related to establishing equivalence between groups with and without language impairments. We conclude with recommendations for practice and future directions in the study of atypical language development

Pupil size tracks semantic ambiguity as well as noise

Effortful listening is experienced by listeners when speech is hard to understand because it is degraded or masked by environmental noise. Pupillometry (i.e., measure of pupil size) can detect effortful listening: pupil size increases when speech is degraded compared to when it is clear. However, the pupil responds to a range of cognitive demands, including linguistic challenges such as syntactic complexity. Here I investigate whether it responds to the need to disambiguate words with more than one meaning, such as ‘bark’ or ‘bank’. Semantic ambiguity is common in English, and previous work indicates that it imposes a processing load. We combine this with an acoustic challenge in a factorial design so the pupil response to these two types of challenge can be directly compared. I found main effects of noise and semantic ambiguity on the pupillary area, indicating that pupil dilation can reflect processes associated with semantic disambiguation as well as noise. Pupil size reflect demands imposed by ambiguity both in the acoustic form of words (i.e. due to degradation) and in word meaning

Identifying Individual Differences in the Neural Correlates of Language Processing Using fMRI

Mapping language functions in the brain is of profound theoretical and clinical interest. The aim of the current Ph.D. project was to develop an fMRI paradigm to assesses different language processes (i.e., phonological, semantic, sentence processing) and modalities (listening, reading, repetition) in a stimulus-driven manner, keeping non-linguistic task demands to a minimum. Cortical activations and functional connectivity patterns were largely in line with previous research, validating the suitability of the paradigm for localizing different language processes. The first empirical chapter of the thesis investigated sentence comprehension in listening and reading, which elicited largely overlapping activations for the two modalities and for semantic and syntactic integration in the left anterior temporal lobe (ATL). Functional connectivity of the left ATL with other parts of the cortical language network differed between the modalities and processes. The second empirical chapter explored individual differences in brain activity in relation to verbal ability. Results supported the notion of more extended as well as stronger activations during language processing in individuals with higher verbal ability, possibly reflecting enhanced processing. The third empirical chapter further investigated individual differences in brain activity, focusing on lateralization in activity as a fundamental principle of how language processing is functionally organized in the brain. Degrees of left-lateralization differed significantly between language processes and were positively related to behaviorally assessed language lateralization. Furthermore, the results provided new evidence supporting a positive relationship between left-lateralization and verbal ability. The thesis concludes with a discussion of the significance of the results with regard to general principles of brain functioning and outlines potential clinical implications

The Effect of Background Music on the Visual Categorization of Printed Words in Normal Younger and Older Adults

Aim: Research has shown that background music, with and without vocal content, has a detrimental effect on cognitive task performance. Research has also shown a decline in processing speed as age increases. The present study seeks to answer the following questions: 1. Will background vocal music have any detrimental effects on performance of a visual semantic word categorization task? 2. Does age have any effect on performance of visual semantic word categorization in the presence of background music? Participants: Participants consisted of 36 adult native speakers of English with normal speech and language divided in to two groups based on age, an older group (63-79 years) and a younger group (18-33 years). The younger group was recruited from the population of students of the University of Tennessee and the Knoxville community. The older group was recruited from the Knoxville Office on Aging and the Knoxville community. Stimuli: Printed words were chosen from superordinate categories such as tools, utensils, animals, food, clothing, furniture, body parts, vehicles, toys, instruments, and insects. The auditory stimulus was Adele’s song “Someone Like You,” from the commercial CD recording. Instrumental recordings of the song were constructed using the music notation software program, Finale and sampled instruments. Procedure: Participants performed a categorization task of printed words on the computer screen in the presence of background music. Participants’ reaction times and the accuracy of their responses were recorded by a software program, SuperLab Pro. The experiment was presented four times consecutively for four randomized auditory conditions consisting of 26 word sets per condition. A questionnaire was administered at the end of the final experiment. Statistical Analysis: A mixed design 2x4 ANOVA was performed (between subjects factor – age group and within-subjects factor – condition) to test the main effects and/or interactions between groups and within groups. Paired sample T-tests were computed to test for comparisons within groups for any significant differences among conditions. Correlations and covariate analyses were performed for questionnaire data. Results: The results did not indicate any significant effect of auditory condition on categorization task performance. Vocal music did not increase reaction times or decrease the accuracy of word categorization. On the other hand, a significant effect of age was found for reaction time and accuracy. Older adults performed significantly more slowly and less accurately than younger adults

Acoustic correlates of encoded prosody in written conversation

This thesis presents an analysis of certain punctuation devices such as parenthesis, italics and emphatic spellings with respect to their acoustic correlates in read speech. The class of punctuation devices under investigation are referred to as prosodic markers. The thesis therefore presents an analysis of features of the spoken language which are represented symbolically in text. Hence it is a characterization of aspects of the spoken language which have been transcribed or symbolized in the written medium and then translated back into a spoken form by a reader. The thesis focuses in particular on the analysis of parenthesis, the examination of encoded prominence and emphasis, and also addresses the use of paralinguistic markers which signal attitude or emotion.In an effort to avoid the use of self constructed or artificial material containing arbitrary symbolic or prosodic encodings, all material used for empirical analysis was taken from examples of electronic written exchanges on the Internet, such as from electronic mail messages and from articles posted on electronic newsgroups and news bulletins. This medium of language, which is referred to here as written conversation, provides a rich source of material containing encoded prosodic markers. These occur in the form of 'smiley faces' expressing attitudes or feelings, words highlighted by a number of means such as capitalization, italics, underscore characters, or asterisks, and in the form of dashes or parentheses, which provide suggestions on how the information in a text or sentence may be structured with regard to its informational content.Chapter 2 investigates in detail the genre of written conversation with respect to its place in an emerging continuum between written and spoken language, concentrating on transcriptional devices and their function as indicators of prosody. The implications these symbolic representations bear on the task of reading, by humans as well as machines, are then examined.Chapters 3 and 4 turn to the acoustic analysis of parentheticals and emphasis markers respectively. The experimental work in this thesis is based on readings of a corpus of selected materials from written conversation with the acoustic analysis concentrating on the differences between readings of texts with prosodic markers and readings of the same texts from which prosodic markers have been removed. Finally, the effect of prosodic markers is tested in perception experiments involving both human and resynthesized utterances

Neural Systems for Reading Aloud: A Multiparametric Approach

Reading aloud involves computing the sound of a word from its visual form. This may be accomplished 1) by direct associations between spellings and phonology and 2) by computation from orthography to meaning to phonology. These components have been studied in behavioral experiments examining lexical properties such as word frequency; length in letters or phonemes; spelling–sound consistency; semantic factors such as imageability, measures of orthographic, or phonological complexity; and others. Effects of these lexical properties on specific neural systems, however, are poorly understood, partially because high intercorrelations among lexical factors make it difficult to determine if they have independent effects. We addressed this problem by decorrelating several important lexical properties through careful stimulus selection. Functional magnetic resonance imaging data revealed distributed neural systems for mapping orthography directly to phonology, involving left supramarginal, posterior middle temporal, and fusiform gyri. Distinct from these were areas reflecting semantic processing, including left middle temporal gyrus/inferior-temporal sulcus, bilateral angular gyrus, and precuneus/posterior cingulate. Left inferior frontal regions generally showed increased activation with greater task load, suggesting a more general role in attention, working memory, and executive processes. These data offer the first clear evidence, in a single study, for the separate neural correlates of orthography–phonology mapping and semantic access during reading aloud