A restricted interaction account (RIA) of spoken word production: The best of both worlds.

Theories of spoken word production generally assume that mapping from conceptual representations (e.g., [furry, feline, domestic]) to phonemes (e.g., /k/, /ae/, /t/) involves both a meaning-based process and a sound-based process. A central question in this framework is how these two processes interact with one another. Two theories that occupy extreme positions on the continuum of interactivity are reviewed: a highly discrete position (e.g., Theories of single word production generally assume that two cognitive processes are required for mapping from a conceptual representations (e.g., [furry, feline, domestic]) to the set of phonemes used to communicate that concept (/k/, /ae/, /t/). The first process is meaning-based (semantic) and involves the selection of a particular word to express a nonverbal concept. The second is sound-based (phonological) and involves retrieving the phonemes that correspond to the selected word To motivate RIA, we first examine highly discrete and interactive theories and carry out a fairly extensive review of the data that are problematic for each. We then show that RIA has the necessary and sufficient features to account for the existing empirical findings and, furthermore, that it can be extended to account for more recent challenges A GENERIC TWO-STAGE FRAMEWORK Theories of spoken word production differ not only in terms of the degree of interactivity that they incorporate, but also with regard to a number of representational and architectural issues. In order to specifically focus on differences among the theories regarding discreteness/interactivity we adopt a ''generic'' architecture that abstracts away from many of the representational differences among current theories. To motivate this generic framework, we first briefly review certain prominent theories of spoken word production. Theories of spoken word production: Representations Most accounts of spoken word production assume a spreading-activation architecture, whereby processing involves sets of units or nodes that accumulate activation and transmit it to other units. The sets of units represent different types of information. Most theories assume separate sets for semantic, syntactic, and phonological information; theories differ, however, in other regards. We briefly review the proposals of Levelt et al

The effects of semantic and orthographic blocking on written word production

In investigating the efficacy of acquired dysgraphia treatments, relatively little attention has been directed to the relationships amongst treated items. Is it beneficial or detrimental to treat together items that belong to the same semantic category or share segments (phonemes or letters)? In spoken production, interference is observed when individuals produce items in the context of other semantically related vs. unrelated items—neurologically normal participants initiate naming more slowly and individuals with aphasia produce more errors (e.g. Damian et al., 2001; Schnur et al., 2006). On the other hand, facilitation is observed for the production of blocks of phonologically related vs. unrelated items— normal participants initiate naming more quickly (e.g. Damian, 2003), although there is some evidence of interference in individuals with aphasia (Hodgson et al., 2005). In the present study, we extend this research to examine the effects of semantic and orthographic blocking on written production in neurologically intact individuals (Experiments 1A and 1B) as well as one individual with acquired dysgraphia (Experiment 2). While the investigation does not involve treatment, the findings may have implications for word retrieval treatment

Examining the Central and Peripheral Processes of Written Word Production Through Meta-Analysis

Producing written words requires “central” cognitive processes (such as orthographic long-term and working memory) as well as more peripheral processes responsible for generating the motor actions needed for producing written words in a variety of formats (handwriting, typing, etc.). In recent years, various functional neuroimaging studies have examined the neural substrates underlying the central and peripheral processes of written word production. This study provides the first quantitative meta-analysis of these studies by applying activation likelihood estimation (ALE) methods (Turkeltaub et al., 2002). For alphabet languages, we identified 11 studies (with a total of 17 experimental contrasts) that had been designed to isolate central and/or peripheral processes of word spelling (total number of participants = 146). Three ALE meta-analyses were carried out. One involved the complete set of 17 contrasts; two others were applied to subsets of contrasts to distinguish the neural substrates of central from peripheral processes. These analyses identified a network of brain regions reliably associated with the central and peripheral processes of word spelling. Among the many significant results, is the finding that the regions with the greatest correspondence across studies were in the left inferior temporal/fusiform gyri and left inferior frontal gyrus. Furthermore, although the angular gyrus (AG) has traditionally been identified as a key site within the written word production network, none of the meta-analyses found it to be a consistent site of activation, identifying instead a region just superior/medial to the left AG in the left posterior intraparietal sulcus. These meta-analyses and the discussion of results provide a valuable foundation upon which future studies that examine the neural basis of written word production can build

Deafness for the meanings of number words

We describe the performance of an aphasic individual who showed a selective impairment affecting his comprehension of auditorily presented number words and not other word categories. His difficulty in number word comprehension was restricted to the auditory modality, given that with visual stimuli (written words, Arabic numerals and pictures) his comprehension of number and non-number words was intact. While there have been previous reports of selective difficulty or sparing of number words at the semantic and post-semantic levels, this is the first reported case of a pre-semantic deficit that is specific to the category of number words. This constitutes evidence that lexical semantic distinctions are respected by modality-specific neural mechanisms responsible for providing access to the meanings of words

Language processing from the perspective of electrical stimulation mapping

Electrical Stimulation (ES) is a neurostimulation technique that is used to localize language functions in the brain of people with intractable epilepsy and/or brain tumors. We reviewed 25 ES articles published between 1984 and 2018 and interpreted them from a cognitive neuropsychological perspective. Our aim was to highlight ES as a tool to further our understanding of cognitive models of language. We focused on associations and dissociations between cognitive functions within the framework of two non-neuroanatomically specified models of language. Also, we discussed parallels between the ES and the stroke literatures and showed how ES data can help us to generate hypotheses regarding how language is processed. A good understanding of cognitive models of language is essential to motivate task selection and to tailor surgical procedures, for example, by avoiding testing the same cognitive functions and understanding which functions may be more or less relevant to be tested during surgery

Cognitive and language performance predicts effects of spelling intervention and tDCS in Primary Progressive Aphasia

Predictors of treatment effects allow individual tailoring of treatment characteristics, thereby saving resources and optimizing outcomes. Electrical stimulation coupled with language intervention has shown promising results in improving language performance in individuals with Primary Progressive Aphasia (PPA). The current study aimed to identify language and cognitive variables associated with response to therapy consisting of language intervention combined with transcranial direct current stimulation (tDCS). Forty individuals with PPA received written naming/spelling intervention combined with anodal tDCS or Sham, using a between-subjects, randomized design, with intervention delivered over a period of 3 weeks. Participants were assessed using a battery of neuropsychological tests before and after each phase. We measured letter accuracy during spelling of trained and untrained words, before, immediately after, 2 weeks, and 2 months after therapy. We used step-wise regression methods to identify variables amongst the neuropsychological measures and experimental factors that were significantly associated with therapy outcomes at each time-point. For trained words, improvement was related to pre-therapy scores, in RAVLT (5 trials sum), pseudoword spelling, object naming, digit span backward, spatial span backward and years post symptom onset. Regarding generalization to untrained words, improvement in spelling was associated with pseudoword spelling, RAVLT proactive interference, RAVLT immediate recall. Generalization effects were larger under tDCS compared to Sham at the 2-month post training measurement. We conclude that, for trained words, patients who improve the most are those who retain for longer language skills such as sublexical spelling processes (phoneme-to-grapheme correspondences) and word retrieval, and other cognitive functions such as executive functions and working memory, and those who have a better learning capacity. Generalization to untrained words occurs through improvement in knowledge of phoneme-to-grapheme correspondences. Furthermore, tDCS enhances the generalizability and duration of therapy effects

Multimodal neural and behavioral data predict response to rehabilitation in chronic post-stroke aphasia

BACKGROUND: Poststroke recovery depends on multiple factors and varies greatly across individuals. Using machine learning models, this study investigated the independent and complementary prognostic role of different patient-related factors in predicting response to language rehabilitation after a stroke. METHODS: Fifty-five individuals with chronic poststroke aphasia underwent a battery of standardized assessments and structural and functional magnetic resonance imaging scans, and received 12 weeks of language treatment. Support vector machine and random forest models were constructed to predict responsiveness to treatment using pretreatment behavioral, demographic, and structural and functional neuroimaging data. RESULTS: The best prediction performance was achieved by a support vector machine model trained on aphasia severity, demographics, measures of anatomic integrity and resting-state functional connectivity (F1=0.94). This model resulted in a significantly superior prediction performance compared with support vector machine models trained on all feature sets (F1=0.82, P<0.001) or a single feature set (F1 range=0.68–0.84, P<0.001). Across random forest models, training on resting-state functional magnetic resonance imaging connectivity data yielded the best F1 score (F1=0.87). CONCLUSIONS: While behavioral, multimodal neuroimaging data and demographic information carry complementary information in predicting response to rehabilitation in chronic poststroke aphasia, functional connectivity of the brain at rest after stroke is a particularly important predictor of responsiveness to treatment, both alone and combined with other patient-related factors.P50 DC012283 - NIDCD NIH HHShttps://www.ahajournals.org/doi/10.1161/STROKEAHA.121.036749Published versio