Coping with phonological assimilation in speech perception : evidence for early compensation

The pronunciation of the same word may vary considerably as a consequence of its context. The Dutch word tuin (English, garden) may be pronounced tuim if followed by bank (English, bench), but not if followed by stoel (English, chair). In a series of four experiments, we examined how Dutch listeners cope with this context sensitivity in their native language. A first word identification experiment showed that the perception of a word-final nasal depends on the subsequent context. Viable assimilations, but not unviable assimilations, were often confused perceptually with canonical word forms in a word identification task. Two control experiments ruled out the possibility that this effect was caused by perceptual masking or was influenced by lexical top-down effects. A passive-listening study in which electrophysiological measurements were used showed that only unviable, but not viable, phonological changes elicited a significant mismatch negativity. The results indicate that phonological assimilations are dealt with by an early prelexical mechanism.peer-reviewe

The role of perceptual integration in the recognition of assimilated word forms

We investigated how spoken words are recognized when they have been altered by phonological assimilation. Previous research has shown that there is a process of perceptual compensation for phonological assimilations. Three recently formulated proposals regarding the mechanisms for compensation for assimilation make different predictions with regard to the level at which compensation is supposed to occur as well as regarding the role of specific language experience. In the present study, Hungarian words and nonwords, in which a viable and an unviable liquid assimilation was applied, were presented to Hungarian and Dutch listeners in an identification task and a discrimination task. Results indicate that viably changed forms are difficult to distinguish from canonical forms independent of experience with the assimilation rule applied in the utterances. This reveals that auditory processing contributes to perceptual compensation for assimilation, while language experience has only a minor role to play when identification is required.peer-reviewe

Atypical White Matter Connectivity in Dyslexic Readers of a Fairly Transparent Orthography

Atypical structural properties of the brain’s white matter bundles have been associated with failing reading acquisition in developmental dyslexia. Because these white matter properties may show dynamic changes with age and orthographic depth, we examined fractional anisotropy (FA) along 16 white matter tracts in 8- to 11-year-old dyslexic (DR) and typically reading (TR) children learning to read in a fairly transparent orthography (Dutch). Our results showed higher FA values in the bilateral anterior thalamic radiations of DRs and FA values of the left thalamic radiation scaled with behavioral reading-related scores. Furthermore, DRs tended to have atypical FA values in the bilateral arcuate fasciculi. Children’s age additionally predicted FA values along the tracts. Together, our findings suggest differential contributions of cortical and thalamo-cortical pathways to the developing reading network in dyslexic and typical readers, possibly indicating prolonged letter-by-letter reading or increased attentional and/or working memory demands in dyslexic children during reading

Orthographic depth and its impact on Universal Predictors of Reading: a cross-language investigation

Alphabetic orthographies differ in the transparency of their letter-sound mappings, with English orthography being less transparent than other alphabetic scripts. The outlier status of English has led scientists to question the generality of findings based on English-language studies. We investigated the role of phonological awareness, memory, vocabulary, rapid naming, and nonverbal intelligence in reading performance across five languages lying at differing positions along a transparency continuum (Finnish, Hungarian, Dutch, Portuguese, and French). Results from a sample of 1,265 children in Grade 2 showed that phonological awareness was the main factor associated with reading performance in each language. However, its impact was modulated by the transparency of the orthography, being stronger in less transparent orthographies. The influence of rapid naming was rather weak and limited to reading and decoding speed. Most predictors of reading performance were relatively universal across these alphabetic languages, although their precise weight varied systematically as a function of script transparenc

fMR-adaptation indicates selectivity to audiovisual content congruency in distributed clusters in human superior temporal cortex

<p>Abstract</p> <p>Background</p> <p>Efficient multisensory integration is of vital importance for adequate interaction with the environment. In addition to basic binding cues like temporal and spatial coherence, meaningful multisensory information is also bound together by content-based associations. Many functional Magnetic Resonance Imaging (fMRI) studies propose the (posterior) superior temporal cortex (STC) as the key structure for integrating meaningful multisensory information. However, a still unanswered question is how superior temporal cortex encodes content-based associations, especially in light of inconsistent results from studies comparing brain activation to semantically matching (congruent) versus nonmatching (incongruent) multisensory inputs. Here, we used fMR-adaptation (fMR-A) in order to circumvent potential problems with standard fMRI approaches, including spatial averaging and amplitude saturation confounds. We presented repetitions of audiovisual stimuli (letter-speech sound pairs) and manipulated the associative relation between the auditory and visual inputs (congruent/incongruent pairs). We predicted that if multisensory neuronal populations exist in STC and encode audiovisual content relatedness, adaptation should be affected by the manipulated audiovisual relation.</p> <p>Results</p> <p>The results revealed an occipital-temporal network that adapted independently of the audiovisual relation. Interestingly, several smaller clusters distributed over superior temporal cortex within that network, adapted stronger to congruent than to incongruent audiovisual repetitions, indicating sensitivity to content congruency.</p> <p>Conclusions</p> <p>These results suggest that the revealed clusters contain multisensory neuronal populations that encode content relatedness by selectively responding to congruent audiovisual inputs, since unisensory neuronal populations are assumed to be insensitive to the audiovisual relation. These findings extend our previously revealed mechanism for the integration of letters and speech sounds and demonstrate that fMR-A is sensitive to multisensory congruency effects that may not be revealed in BOLD amplitude per se.</p

In search of the auditory, phonetic, and/or phonological problems in dyslexia: Context effects in speech perception

There is a growing consensus that developmental dyslexia is associated with a phonological-core deficit. One symptom of this phonological deficit is a subtle speech-perception deficit. The auditory basis of this deficit is still hotly debated. If people with dyslexia, however, do not have an auditory deficit and perceive the underlying acoustic dimensions of speech as well as people who read normally, then why do they exhibit a categorical-perception deficit? A potential answer to this conundrum lies in the possibility that people with dyslexia do not adequately handle the context-dependent variation that speech signals typically contain. A mathematical model simulating such a sensitivity deficit mimics the speechperception deficits attributed to dyslexia. To assess the nature of the dyslexic problem, the authors examined whether children with dyslexia handle context dependencies in speech differently than do normal-reading individuals. Contrary to the initial hypothesis, children with dyslexia did not show less context sensitivity in speech perception than did normal-reading individuals at auditory, phonetic, and phonological levels of processing, nor did they reveal any categorization deficit. Instead, intrinsic properties of online phonological processes, not phonological representations per se, may be impaired in dyslexia. KEY WORDS: developmental dyslexia, speech perception, categorical perception, context effects, phonological deficit Developmental dyslexia refers to poor reading and writing abilities in spite of adequate intelligence and in the absence of any sensory disorder or neuropsychological signs. People with dyslexia, however, not only are impaired in reading but also show subtle deficits on a range of tasks that probe phonological processing and do not involve written material. People with dyslexia have been shown to be subtly impaired on tasks that involve repeating words and nonword

Exploring the Role of Low Level Visual Processing in Letter-Speech Sound Integration: A Visual MMN Study

In contrast with for example audiovisual speech, the relation between visual and auditory properties of letters and speech sounds is artificial and learned only by explicit instruction. The arbitrariness of the audiovisual link together with the widespread usage of letter-speech sound pairs in alphabetic languages makes those audiovisual objects a unique subject for crossmodal research. Brain imaging evidence has indicated that heteromodal areas in superior temporal, as well as modality-specific auditory cortex are involved in letter-speech sound processing. The role of low level visual areas, however, remains unclear. In this study the visual counterpart of the auditory mismatch negativity (MMN) is used to investigate the influences of speech sounds on letter processing. Letter and non-letter deviants were infrequently presented in a train of standard letters, either in isolation or simultaneously with speech sounds. Although previous findings showed that letters systematically modulate speech sound processing (reflected by auditory MMN amplitude modulation), the reverse does not seem to hold: our results did not show evidence for an automatic influence of speech sounds on letter processing (no visual MMN amplitude modulation). This apparent asymmetric recruitment of low level sensory cortices during letter-speech sound processing, contrasts with the symmetric involvement of these cortices in audiovisual speech processing, and is possibly due to the arbitrary nature of the link between letters and speech sounds