Limits to tDCS effects in language:failures to modulate word production in healthy participants with frontal or temporal tDCS

Transcranial direct current stimulation (tDCS) is a method of non-invasive brain stimulation widely used to modulate cognitive functions. Recent studies, however, suggests that effects are unreliable, small and often non-significant at least when stimulation is applied in a single session to healthy individuals. We examined the effects of frontal and temporal lobe anodal tDCS on naming and reading tasks and considered possible interactions with linguistic activation and selection mechanisms as well possible interactions with item difficulty and participant individual variability. Across four separate experiments (N, Exp 1A = 18; 1B = 20; 1C = 18; 2 = 17), we failed to find any difference between real and sham stimulation. Moreover, we found no evidence of significant effects limited to particular conditions (i.e., those requiring suppression of semantic interference), to a subset of participants or to longer RTs. Our findings sound a cautionary note on using tDCS as a means to modulate cognitive performance. Consistent effects of tDCS may be difficult to demonstrate in healthy participants in reading and naming tasks, and be limited to cases of pathological neurophysiology and/or to the use of learning paradigms.

Effects of syllable structure in aphasic errors:implications for a new model of speech production

Current models of word production assume that words are stored as linear sequences of phonemes which are structured into syllables only at the moment of production. This is because syllable structure is always recoverable from the sequence of phonemes. In contrast, we present theoretical and empirical evidence that syllable structure is lexically represented. Storing syllable structure would have the advantage of making representations more stable and resistant to damage. On the other hand, re-syllabifications affect only a minimal part of phonological representations and occur only in some languages and depending on speech register. Evidence for these claims comes from analyses of aphasic errors which not only respect phonotactic constraints, but also avoid transformations which move the syllabic structure of the word further away from the original structure, even when equating for segmental complexity. This is true across tasks, types of errors, and, crucially, types of patients. The same syllabic effects are shown by apraxic patients and by phonological patients who have more central difficulties in retrieving phonological representations. If syllable structure was only computed after phoneme retrieval, it would have no way to influence the errors of phonological patients. Our results have implications for psycholinguistic and computational models of language as well as for clinical and educational practices.

Phonological–lexical activation:a lexical component or anoutput buffer? Evidence from aphasic errors

Single word production requires that phoneme activation is maintained while articulatory conversion is taking place. Word serial recall, connected speech and non-word production (repetition and spelling) are all assumed to involve a phonological output buffer. A crucial question is whether the same memory resources are also involved in single word production. We investigate this question by assessing length and positional effects in the single word repetition and reading of six aphasic patients. We expect a damaged buffer to result in error rates per phoneme which increase with word length and in position effects. Although our patients had trouble with phoneme activation (they made mainly errors of phoneme selection), they did not show the effects expected from a buffer impairment. These results show that phoneme activation cannot be automatically equated with a buffer. We hypothesize that the phonemes of existing words are kept active though permanent links to the word node. Thus, the sustained activation needed for their articulation will come from the lexicon and will have different characteristics from the activation needed for the short-term retention of an unbound set of units. We conclude that there is no need and no evidence for a phonological buffer in single word production.

Non-verbal signalling in digital discourse:the case of letter repetition

This study focuses on the interactional functions of non-standard spelling, in particular letter repetition, used in text-based computer-mediated communication as a means of non-verbal signalling. The aim of this paper is to assess the current state of non-verbal cue research in computer-mediated discourse and demonstrate the need for a more comprehensive and methodologically rigorous exploration of written non-verbal signalling. The study proposes a contextual and usage-centered view of written paralanguage. Through illustrative, close linguistic analyses the study proves that previous approaches to non-standard spelling based on their relation to the spoken word might not account for the complexities of this CMC cue, and in order to further our understanding of their interactional functions it is more fruitful to describe the role they play during the contextualisation of the verbal messages. The interactional sociolinguistic approach taken in the analysis demonstrates the range of interactional functions letter repetition can achieve, including contribution to the inscription of socio-emotional information into writing, to the evoking of auditory cues or to a display of informality through using a relaxed writing style.

Word order in Yiddish narrative discourse

Based on data from spoken narrative discourse in Yiddish, this paper analyses two structures common in Yiddish narrations: The placement of the finite verb in the first position of a declarative sentence, and topicalization.Like German, Yiddish word order is generally centered around a verb-second rule. However, both Yiddish and spoken German show configurations of word order that go against the rule, where the finite verb occupies the first position of the utterance. From a functional-pragmatic point of view, these structures can be said to serve special purposes in the interaction between speaker and listener, sometimes in particular discourse types.Differences and similarities in word order between Yiddish and German enable us to comment on the relationship between these two closely related languages.

Concreteness effects in different tasks: implications for models of short-term memory

This study investigates concreteness effects in tasks requiring short-term retention. Concreteness effects were assessed in serial recall, matching span, order reconstruction, and free recall. Each task was carried out both in a control condition and under articulatory suppression. Our results show no dissociation between tasks that do and do not require spoken output. This argues against the redintegration hypothesis according to which lexical-semantic effects in short-term memory arise only at the point of production. In contrast, concreteness effects were modulated by task demands that stressed retention of item versus order information. Concreteness effects were stronger in free recall than in serial recall. Suppression, which weakens phonological representations, enhanced the concreteness effect with item scoring. In a matching task, positive effects of concreteness occurred with open sets but not with closed sets of words. Finally, concreteness effects reversed when the task asked only for recall of word positions (as in the matching task), when phonological representations were weak (because of suppression), and when lexical semantic representations overactivated (because of closed sets). We interpret these results as consistent with a model where phonological representations are crucial for the retention of order, while lexical-semantic representations support maintenance of item identity in both input and output buffers.

The roles of family history of dyslexia, language, speech production and phonological processing in predicting literacy progress

It is well established that speech, language and phonological skills are closely associated with literacy, and that children with a family risk of dyslexia (FRD) tend to show deficits in each of these areas in the preschool years. This paper examines what the relationships are between FRD and these skills, and whether deficits in speech, language and phonological processing fully account for the increased risk of dyslexia in children with FRD. One hundred and fifty-three 4-6-year-old children, 44 of whom had FRD, completed a battery of speech, language, phonology and literacy tasks. Word reading and spelling were retested 6 months later, and text reading accuracy and reading comprehension were tested 3 years later. The children with FRD were at increased risk of developing difficulties in reading accuracy, but not reading comprehension. Four groups were compared: good and poor readers with and without FRD. In most cases good readers outperformed poor readers regardless of family history, but there was an effect of family history on naming and nonword repetition regardless of literacy outcome, suggesting a role for speech production skills as an endophenotype of dyslexia. Phonological processing predicted spelling, while language predicted text reading accuracy and comprehension. FRD was a significant additional predictor of reading and spelling after controlling for speech production, language and phonological processing, suggesting that children with FRD show additional difficulties in literacy that cannot be fully explained in terms of their language and phonological skills. It is well established that speech, language and phonological skills are closely associated with literacy, and that children with a family risk of dyslexia (FRD) tend to show deficits in each of these areas in the preschool years. This paper examines what the relationships are between FRD and these skills, and whether deficits in speech, language and phonological processing fully account for the increased risk of dyslexia in children with FRD. One hundred and fifty-three 4-6-year-old children, 44 of whom had FRD, completed a battery of speech, language, phonology and literacy tasks. © 2014 John Wiley & Sons Ltd.