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Neural circuitry associated with two different approaches to novel word learning

Skilled reading depends upon successfully integrating orthographic, phonological, and semantic information; however, the process of becoming a skilled reader with efficient neural circuitry is not fully understood. Short-term learning paradigms can provide insight into learning mechanisms by revealing differential responses to training approaches. To date, neuroimaging studies have primarily focused on effects of teaching novel words either in isolation or in context, without directly comparing the two. The current study compared the behavioral and neurobiological effects of learning novel pseudowords (i.e., pronouncing and attaching meaning) trained either in isolation or in sentential context. Behavioral results showed generally comparable pseudoword learning for both conditions, but sentential context-trained pseudowords were spoken and comprehended slightly more quickly. Neurobiologically, fMRI activity for reading trained pseudowords was similar to real words; however, an interaction between training approach and reading proficiency was observed. Specifically, highly skilled readers showed similar levels of activity regardless of training approach. However, less skilled readers differentiated between training conditions, showing comparable activity to highly skilled readers only for isolation-trained pseudowords. Overall, behavioral and neurobiological findings suggest that training approach may affect rate of learning and neural circuitry, and that less skilled readers may need explicit training to develop optimal neural pathways.

from Developmental Cognitive Neuroscience

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Is developmental dyslexia modality specific? A visual auditory comparison of Italian dyslexics

Although developmental dyslexia is often referred to as a cross-modal disturbance, tests of different modalities using the same stimuli are lacking. We compared the performance of 23 children with dyslexia and 42 chronologically matched control readers on reading versus repetition tasks and visual versus auditory lexical decision using the same stimuli. With respect to control readers, children with dyslexia were impaired only on stimuli in the visual modality; they had no deficit on the repetition and auditory lexical decision tasks. By applying the rate-amount model (Faust et al., 1999), we showed that performance of children with dyslexia on visual (but not auditory) tasks was associated with that of control readers by a linear relationship (with a 1.78 slope), suggesting that a global factor accounts for visual (but not auditory) task performance.

from Neuropsychologia

Remembering ‘zeal’ but not ‘thing’: Reverse frequency effects as a consequence of deregulated semantic processing

More efficient processing of high frequency (HF) words is a ubiquitous finding in healthy individuals, yet frequency effects are often small or absent in stroke aphasia. We propose that some patients fail to show the expected frequency effect because processing of HF words places strong demands on semantic control and regulation processes, counteracting the usual effect. This may occur because HF words appear in a wide range of linguistic contexts, each associated with distinct semantic information. This theory predicts that in extreme circumstances, patients with impaired semantic control should show an outright reversal of the normal frequency effect. To test this prediction, we tested two patients with impaired semantic control with a delayed repetition task that emphasised activation of semantic representations. By alternating HF and low frequency (LF) trials, we demonstrated a significant repetition advantage for LF words, principally because of perseverative errors in which patients produced the previous LF response in place of the HF target. These errors indicated that HF words were more weakly activated than LF words. We suggest that when presented with no contextual information, patients generate a weak and unstable pattern of semantic activation for HF words because information relating to many possible contexts and interpretations is activated. In contrast, LF words tend to associate with more stable patterns of activation because similar semantic information is activated whenever they are encountered.

from Neuropsychologia

Some Prosodic Characteristics of Repeated Talk following Conversation Repair Requests by Adults with Hearing Impairment

When miscommunications occur in conversation, participants have access to both speech- and language-based cues to clarify the miscommunicated talk. This article investigates what changes occur in prosodic speech patterns between initial and repeated talk in a brief free and unstructured conversation between an adult bilateral cochlear implantee and his chosen familiar communication partner, his wife, conducted in a clinical setting. The 23-minute conversation between the two participants included 37 self-repetitions of one or more words by the familiar communication partner. Most instances were repetition-as-repair sequences. Each of the 37 instances was subjected to acoustic analysis to identify frequency, loudness, and duration of word tokens in both the initial and repeated talk as well as pause length between tokens. Data suggest that loudness, pitch, and duration are commonly all increased in the prominent words repeated by the communication partner by contrast with the initial utterance. Repeated sequences included more pauses, but not longer ones, than the initial utterances. Prosodic patterns of repetition were influenced by the turn(s) preceding the repeated talk and the co-occurrence of prosodic and lexical elements in the repair/repetition turn. The success of the repeated talk in resolving miscommunications for this dyad suggests that prosodic speech cues in conjunction with lexical cues are effective repair strategies.

from Seminars in Hearing

Naming and repetition in aphasia: Steps, routes, and frequency effects

This paper investigates the cognitive processes underlying picture naming and auditory word repetition. In the two-step model of lexical access, both the semantic and phonological steps are involved in naming, but the former has no role in repetition. Assuming recognition of the to-be-repeated word, repetition could consist of retrieving the word’s output phonemes from the lexicon (the lexical-route model), retrieving the output phonology directly from input phonology (the nonlexical-route model) or employing both routes together (the summation dual-route model). We tested these accounts by comparing the size of the word frequency effect (an index of lexical retrieval) in naming and repetition data from 59 aphasic patients with simulations of naming and repetition models. The magnitude of the frequency effect (and the influence of other lexical variables) was found to be comparable in naming and repetition, and equally large for both the lexical and summation dual-route models. However, only the dual-route model was fully consistent with data from patients, suggesting that nonlexical input is added on top of a fully-utilized lexical route.

from the Journal of Memory and Language

Some Prosodic Characteristics of Repeated Talk following Conversation Repair Requests by Adults with Hearing Impairment

When miscommunications occur in conversation, participants have access to both speech- and language-based cues to clarify the miscommunicated talk. This article investigates what changes occur in prosodic speech patterns between initial and repeated talk in a brief free and unstructured conversation between an adult bilateral cochlear implantee and his chosen familiar communication partner, his wife, conducted in a clinical setting. The 23-minute conversation between the two participants included 37 self-repetitions of one or more words by the familiar communication partner. Most instances were repetition-as-repair sequences. Each of the 37 instances was subjected to acoustic analysis to identify frequency, loudness, and duration of word tokens in both the initial and repeated talk as well as pause length between tokens. Data suggest that loudness, pitch, and duration are commonly all increased in the prominent words repeated by the communication partner by contrast with the initial utterance. Repeated sequences included more pauses, but not longer ones, than the initial utterances. Prosodic patterns of repetition were influenced by the turn(s) preceding the repeated talk and the co-occurrence of prosodic and lexical elements in the repair/repetition turn. The success of the repeated talk in resolving miscommunications for this dyad suggests that prosodic speech cues in conjunction with lexical cues are effective repair strategies.

from Seminars in Hearing

The neural architecture of discourse compression

Re-telling a story is thought to produce a progressive refinement in the mental representation of the discourse. A neuroanatomical substrate for this compression effect, however, has yet to be identified. We used a discourse re-listening task and functional magnetic resonance imaging (fMRI) to identify brain regions responsive to repeated discourse in twenty healthy volunteers. We found a striking difference in the pattern of activation associated with the first and subsequent presentations of the same story relative to rest. The first presentation was associated with a highly significant increase in blood oxygen level dependent (BOLD) signal in a bilateral perisylvian distribution, including auditory cortex. Listening to the same story on subsequent occasions revealed a wider network with activation extending into frontal, parietal, and subcortical structures. When the first and final presentations of the same story were directly compared, significant increments in activation were found in the middle frontal gyrus bilaterally, and the right inferior parietal lobule, suggesting that the spread of activation with re-listening reflected an active neural process over and above that required for comprehension of the text. Within the right inferior parietal region the change in BOLD signal was highly correlated with a behavioural index of discourse compression based in re-telling, providing converging evidence for the role of the right inferior parietal region in the representation of discourse. Our findings demonstrate, for the first time, the existence of a neural network underlying discourse compression, showing that parts of this network are common to re-telling and re-listening effects.

from Neuropsychologia

Connectionist diagnosis of lexical disorders in aphasia

Background: In the cognitive neurolinguistic approach to lexical deficits in aphasia, impaired levels of processing are localised in a cognitive model. Model-oriented treatment may target these impaired components. Thus a precise assessment of the disorder is crucial. Connectionist models add to this by using computer simulation to specify the details of the functioning of these components. The connectionist semantic-phonological model of lexical access (Dell, Martin, & Schwartz, 2007; Schwartz, Dell, Martin, Gahl, & Sobel, 2006) explores the impairment by simulating error patterns in naming and repetition.

Aims: The purpose of the present study was to investigate the model’s range of application as a diagnostic tool, and to derive recommendations for the model’s use in clinical settings.

Methods & Procedures: We demonstrate how we adapted the error analysis to 15 German-speaking patients with aphasia, analysed the model’s accuracy in assessing naming and repetition disorders, and explained deviations between the error pattern produced by each patient and the one produced by the model’s simulation by appealing to an extended version of the model.

Outcomes & Results: Overall, the model yielded good fits of the patients’ error patterns. Larger model-patient deviations could be explained by the model’s limited set of lesionable components.

Conclusions: The “connectionist diagnosis” of naming and repetition disorders in the semantic-phonological model is a reasonable tool in model-oriented assessment. However, the diagnosis needs to be complemented by further language tests.

from Aphasiology

Uses and interpretations of non-word repetition tasks in children with and without specific language impairments (SLI)

from the International Journal of Language and Communication Disorders

Conclusions: Because repetition accuracy depends on lexical and sublexical properties, the NRT can be used to examine the structural properties of the lexicon in both children with NL and with SLI. Further, because the task taps so many underlying skills, it is a powerful tool that can be used to identify children with language impairments.

Going on with optimised feet: Evidence for the interaction between segmental and metrical structure in phonological encoding from a case of primary progressive aphasia

from Aphasiology

Conclusions: The present data provide evidence for specific forms of interaction between segmental and metrical knowledge: On the one hand, segmental information influenced the patient’s stress assignment errors in reading. On the other hand, prosodic information modified segmental errors even in severe jargon observed in repetition. With respect to the prosodic system of German, the observed error patterns show that the structure of the final syllable determines how syllables of a word are parsed into prosodic feet and, accordingly, which syllable has to be prominent. Thus, our results support quantity-sensitive approaches of stress assignment.