Phonological processing in primary progressive aphasia

Primary progressive aphasia (PPA) is a debilitating condition wherein speech and language deteriorate as a result of neurodegenerative disease. Three variants of PPA are now recognized, each of which shows a unique constellation of speech-language deficits and pattern of underlying atrophy in the brain (Gorno-Tempini et al., 2011). The variants include a nonfluent/agrammatic type (nfvPPA), characterized by syntactic and motor speech deficits and fronto-insular atrophy in the left hemisphere. The semantic variant (svPPA) shows degradation of semantic knowledge in the context of anterior and inferior temporal lobe atrophy (left hemisphere greater than right). Finally, the more recently characterized logopenic variant (lvPPA) shows impairments in naming and repetition that are thought to be phonological in nature. This variant, associated with atrophy of temporoparietal regions in the left hemisphere, has also been referred to as the “phonological” variant of PPA due to observed deficits on tasks that require phonological storage (i.e., the “phonological loop”) and to the presence of phonological paraphasias in connected speech (Gorno-Tempini et al., 2008). Impaired phonological processing has been considered a unique feature of the logopenic variant of PPA, however, phonological skills have not been thoroughly characterized across the three variants. Recent models of the functional neuroanatomy of language propose two pathways by which speech is processed in the brain (Hickok & Poeppel, 2007). A dorsal pathway involving temporoparietal and posterior frontal structures is thought to be involved in mapping phonological representations onto articulatory representations. A ventral pathway located in the middle and inferior temporal lobes is considered crucial for mapping phonological representations onto lexical-semantic representations. Both the dorsal and ventral streams emanate from a common cortical region in posterior, superior temporal cortex/sulcus that appears critical to the mental representation of phonology. We investigated phonological processing in PPA, with the goal of identifying whether patterns of performance in the different variants support this functional-anatomical framework. Based on our knowledge of the locus of anatomical damage in the subtypes of PPA, we hypothesized that patients with damage to dorsal route structures (nonfluent and logopenic variants) would show greater impairment on phonological processing tasks, whereas patients with damage to ventral route structures (semantic variant) would show relative preservation of phonological abilities

Statistical distributions of consonant variants in infant-directed speech: evidence that /t/ may be exceptional

Statistical distributions of phonetic variants in spoken language influence speech perception for both language learners and mature users. We theorized that patterns of phonetic variant processing of consonants demonstrated by adults might stem in part from patterns of early exposure to statistics of phonetic variants in infant-directed (ID) speech. In particular, we hypothesized that ID speech might involve greater proportions of canonical /t/ pronunciations compared to adult-directed (AD) speech in at least some phonological contexts. This possibility was tested using a corpus of spontaneous speech of mothers speaking to other adults, or to their typically-developing infant. Tokens of word-final alveolar stops – including /t/, /d/, and the nasal stop /n/ – were examined in assimilable contexts (i.e., those followed by a word-initial labial and/or velar); these were classified as canonical, assimilated, deleted, or glottalized. Results confirmed that there were significantly more canonical pronunciations in assimilable contexts in ID compared with AD speech, an effect which was driven by the phoneme /t/. These findings suggest that at least in phonological contexts involving possible assimilation, children are exposed to more canonical /t/ variant pronunciations than adults are. This raises the possibility that perceptual processing of canonical /t/ may be partly attributable to exposure to canonical /t/ variants in ID speech. Results support the need for further research into how statistics of variant pronunciations in early language input may shape speech processing across the lifespan

Can children with speech difficulties process an unfamiliar accent?

This study explores the hypothesis that children identified as having phonological processing problems may have particular difficulty in processing a different accent. Children with speech difficulties (n = 18) were compared with matched controls on four measures of auditory processing. First, an accent auditory lexical decision task was administered. In one condition, the children made lexical decisions about stimuli presented in their own accent (London). In the second condition, the stimuli were spoken in an unfamiliar accent (Glaswegian). The results showed that the children with speech difficulties had a specific deficit on the unfamiliar accent. Performance on the other auditory discrimination tasks revealed additional deficits at lower levels of input processing. The wider clinical implications of the findings are considered

Life on the Edge: A sociophonological analysis of diphthong variation and change

This paper presents an innovative socio-phonological analysis of dialect variation and change. The analysis uses sociolinguistic data regarding the diphthongs |au|, |ai| and |ei| in Mersea Island English, a variety of British English. The trajectory of change shown by the data, as well as certain aspects of contextual variation (namely Canadian Raising) will provide the basis for outlining a three-tiered model that represents both internal (linguistic) and external (sociolinguistic) factors on variation and, ultimately, change . The model draws on the mechanics of both Dispersion Theory and Optimality Theory. This allows for system optimisation in the underlying phonology to be represented alongside optimal candidate selections after phonetic contextual information becomes available. The outputs from these levels, together with other possible surface variants, are then shown to have sociolinguistic associations that influence which form is ultimately selected as the surface form

Sleep May Not Benefit Learning New Phonological Categories

It is known that sleep participates in memory consolidation processes. However, results obtained in the auditory domain are inconsistent. Here we aimed at investigating the role of post-training sleep in auditory training and learning new phonological categories, a fundamental process in speech processing. Adult French-speakers were trained to identify two synthetic speech variants of the syllable /d∂/ during two 1-h training sessions. The 12-h interval between the two sessions either did (8 p.m. to 8 a.m. ± 1 h) or did not (8 a.m. to 8 p.m. ± 1 h) included a sleep period. In both groups, identification performance dramatically improved over the first training session, to slightly decrease over the 12-h offline interval, although remaining above chance levels. Still, reaction times (RT) were slowed down after sleep suggesting higher attention devoted to the learned, novel phonological contrast. Notwithstanding, our results essentially suggest that post-training sleep does not benefit more than wakefulness to the consolidation or stabilization of new phonological categories

Working Memory in Writing: Empirical Evidence From the Dual-Task Technique

The dual-task paradigm recently played a major role in understanding the role of working memory in writing. By reviewing recent findings in this field of research, this article highlights how the use of the dual-task technique allowed studying processing and short-term storage functions of working memory involved in writing. With respect to processing functions of working memory (namely, attentional and executive functions), studies investigated resources allocation, step-by-step management and parallel coordination of the writing processes. With respect to short-term storage in working memory, experiments mainly attempted to test Kellogg's (1996) proposals on the relationship between the writing processes and the slave systems of working memory. It is concluded that the dual-task technique revealed fruitful in understanding the relationship between writing and working memory

Research methods and intelligibility studies

This paper first briefly reviews the concept of intelligibility as it has been employed in both English as a Lingua Franca (ELF) and world Englishes (WE) research. It then examines the findings of the Lingua Franca Core (LFC), a list of phonological features that empirical research has shown to be important for safeguarding mutual intelligibility between non-native speakers of English. The main point of the paper is to analyse these findings and demonstrate that many of them can be explained if three perspectives (linguistic, psycholinguistic and historical-variationist) are taken. This demonstration aims to increase the explanatory power of the concept of intelligibility by providing some theoretical background. An implication for ELF research is that at the phonological level, internationally intelligible speakers have a large number of features in common, regardless of whether they are non-native speakers or native speakers. An implication for WE research is that taking a variety-based, rather than a features-based, view of phonological variation and its connection with intelligibility is likely to be unhelpful, as intelligibility depends to some extent on the phonological features of individual speakers, rather than on the varieties per se