Karin A. Buetler

Language context modulates reading route: an electrical neuroimaging study.

Introduction: The orthographic depth hypothesis (Katz and Feldman, 1983) posits that different reading routes are engaged depending on the type of grapheme/phoneme correspondence of the language being read. Shallow orthographies with consistent grapheme/phoneme correspondences favor encoding via non-lexical pathways, where each grapheme is sequentially mapped to its corresponding phoneme. In contrast, deep orthographies with inconsistent grapheme/phoneme correspondences favor lexical pathways, where phonemes are retrieved from specialized memory structures. This hypothesis, however, lacks compelling empirical support. The aim of the present study was to investigate the impact of orthographic depth on reading route selection using a within-subject design. Method: We presented the same pseudowords (PWs) to highly proficient bilinguals and manipulated the orthographic depth of PW reading by embedding them among two separated German or French language contexts, implicating respectively, shallow or deep orthography. High density electroencephalography was recorded during the task. Results: The topography of the ERPs to identical PWs differed 300–360 ms post-stimulus onset when the PWs were read in different orthographic depth context, indicating distinct brain networks engaged in reading during this time window. The brain sources underlying these topographic effects were located within left inferior frontal (German > French), parietal (French > German) and cingular areas (German > French). Conclusion: Reading in a shallow context favors non-lexical pathways, reflected in a stronger engagement of frontal phonological areas in the shallow versus the deep orthographic context. In contrast, reading PW in a deep orthographic context recruits less routine non-lexical pathways, reflected in a stronger engagement of visuo-attentional parietal areas in the deep versus shallow orthographic context. These collective results support a modulation of reading route by orthographic depth.

Electrical neuroimaging during auditory motion aftereffects reveals that auditory motion processing is motion sensitive but not direction selective

Following prolonged exposure to adaptor sounds moving in a single direction, participants may perceive stationary-probe sounds as moving in the opposite direction [direction-selective auditory motion aftereffect (aMAE)] and be less sensitive to motion of any probe sounds that are actually moving (motion-sensitive aMAE). The neural mechanisms of aMAEs, and notably whether they are due to adaptation of direction-selective motion detectors, as found in vision, is presently unknown and would provide critical insight into auditory motion processing. We measured human behavioral responses and auditory evoked potentials to probe sounds following four types of moving-adaptor sounds: leftward and rightward unidirectional, bidirectional, and stationary. Behavioral data replicated both direction-selective and motion-sensitive aMAEs. Electrical neuroimaging analyses of auditory evoked potentials to stationary probes revealed no significant difference in either global field power (GFP) or scalp topography between leftward and rightward conditions, suggesting that aMAEs are not based on adaptation of direction-selective motion detectors. By contrast, the bidirectional and stationary conditions differed significantly in the stationary-probe GFP at 200 ms poststimulus onset without concomitant topographic modulation, indicative of a difference in the response strength between statistically indistinguishable intracranial generators. The magnitude of this GFP difference was positively correlated with the magnitude of the motion-sensitive aMAE, supporting the functional relevance of the neurophysiological measures. Electrical source estimations revealed that the GFP difference followed from a modulation of activity in predominantly right hemisphere frontal-temporal-parietal brain regions previously implicated in auditory motion processing. Our collective results suggest that auditory motion processing relies on motion-sensitive, but, in contrast to vision, non-direction-selective mechanisms.

Balanced bilinguals favor lexical processing in their opaque language and conversion system in their shallow language.

Referred to as orthographic depth, the degree of consistency of grapheme/phoneme correspondences varies across languages from high in shallow orthographies to low in deep orthographies. The present study investigates the impact of orthographic depth on reading route by analyzing evoked potentials to words in a deep (French) and shallow (German) language presented to highly proficient bilinguals. ERP analyses to German and French words revealed significant topographic modulations 240-280 ms post-stimulus onset, indicative of distinct brain networks engaged in reading over this time window. Source estimations revealed that these effects stemmed from modulations of left insular, inferior frontal and dorsolateral regions (German>French) previously associated to phonological processing. Our results show that reading in a shallow language was associated to a stronger engagement of phonological pathways than reading in a deep language. Thus, the lexical pathways favored in word reading are reinforced by phonological networks more strongly in the shallow than deep orthography.

The Impact of Language Opacity and Proficiency on Reading Strategies in Bilinguals: An Eye Movement Study

Reading strategies vary across languages according to orthographic depth – the complexity of the grapheme in relation to phoneme conversion rules – notably at the level of eye movement patterns. We recently demonstrated that a group of early bilinguals, who learned both languages equally under the age of seven, presented a first fixation location (FFL) closer to the beginning of words when reading in German as compared with French. Since German is known to be orthographically more transparent than French, this suggested that different strategies were being engaged depending on the orthographic depth of the used language. Opaque languages induce a global reading strategy, and transparent languages force a local/serial strategy. Thus, pseudo-words were processed using a local strategy in both languages, suggesting that the link between word forms and their lexical representation may also play a role in selecting a specific strategy. In order to test whether corresponding effects appear in late bilinguals with low proficiency in their second language (L2), we present a new study in which we recorded eye movements while two groups of late German–French and French–German bilinguals read aloud isolated French and German words and pseudo-words. Since, a transparent reading strategy is local and serial, with a high number of fixations per stimuli, and the level of the bilingual participants’ L2 is low, the impact of language opacity should be observed in L1. We therefore predicted a global reading strategy if the bilinguals’ L1 was French (FFL close to the middle of the stimuli with fewer fixations per stimuli) and a local and serial reading strategy if it was German. Thus, the L2 of each group, as well as pseudo-words, should also require a local and serial reading strategy. Our results confirmed these hypotheses, suggesting that global word processing is only achieved by bilinguals with an opaque L1 when reading in an opaque language; the low level in the L2 gives way to a local and serial reading strategy. These findings stress the fact that reading behavior is influenced not only by the linguistic mode but also by top–down factors, such as readers’ proficiency.

The modulation of reading strategies by language opacity in early bilinguals: an eye movement study

Converging evidences from eye movement experiments indicate that linguistic contexts influence reading strategies. However, the question of whether different linguistic contexts modulate eye movements during reading in the same bilingual individuals remains unresolved. We examined reading strategies in a transparent (German) and an opaque (French) language of early, highly proficient French–German bilinguals: participants read aloud isolated French and German words and pseudo-words while the First Fixation Location (FFL), its duration and latency were measured. Since transparent linguistic contexts and pseudo-words would favour a direct grapheme/phoneme conversion, the reading strategy should be more local for German than for French words (FFL closer to the beginning) and no difference is expected in pseudo-words’ FFL between contexts. Our results confirm these hypotheses, providing the first evidence that the same individuals engage different reading strategy depending on language opacity, suggesting that a given brain process can be modulated by a given context.

Behavioral and electrophysiological signatures of word translation processes

&NA; Translation is a demanding process during which a message is analyzed, translated and communicated from one language to another. Despite numerous studies on translation mechanisms, the electrophysiological processes underlying translation with overt production remain largely unexplored. Here, we investigated how behavioral response patterns and spatial‐temporal brain dynamics differ in a translation compared to a control within‐language word‐generation task. We also investigated how forward and backward translation differs on the behavioral and electrophysiological level. To address these questions, healthy late bilingual subjects performed a translation and a within‐language control task while a 128‐channel EEG was recorded. Behavioral data showed faster responses for translation compared to within‐language word generation and faster responses for backward than forward translation. The ERP‐analysis revealed stronger early (< 200 ms) preparatory and attentional processes for between than within word generation. Later (424–630 ms) differences were characterized by distinct engagement of domain‐general control networks, namely self‐monitoring and lexical access interference. Language asymmetry effects occurred at a later stage (600 ms), reflecting differences in conceptual processing characterized by a larger involvement of areas implicated in attention, arousal and awareness for forward versus backward translation. HighlightsBehavioral responses are faster for backward than forward translation.Responses are faster in simultaneous translation than within‐language word generation.Neural attentional and self‐monitoring effects are stronger in translation.Lexical access interference needs more control in within‐language word generation.Late language asymmetry effects reflect differences in conceptual processing.

Dorsolateral Prefrontal Transcranial Direct Current Stimulation Modulates Language Processing but Does Not Facilitate Overt Second Language Word Production

Word retrieval in bilingual speakers partly depends on executive control systems in the left prefrontal cortex – including dorsolateral prefrontal cortex (DLPFC). We tested the hypothesis that DLPFC modulates word production of words specifically in a second language (L2) by measuring the effects of anodal transcranial direct current stimulation (anodal-tDCS) over the DLPFC on picture naming and word translation and on event-related potentials (ERPs) and their sources. Twenty-six bilingual participants with “unbalanced” proficiency in two languages were given 20 min of 1.5 mA anodal or sham tDCS (double-blind stimulation design, counterbalanced stimulation order, 1-week intersession delay). The participants then performed the following tasks: verbal and non-verbal fluency during anodal-tDCS stimulation and first and second language (L1 and L2) picture naming and translation [forward (L1 → L2) and backward (L2 → L1)] immediately after stimulation. The electroencephalogram (EEG) was recorded during picture naming and translation. On the behavioral level, anodal-tDCS had an influence on non-verbal fluency but neither on verbal fluency, nor on picture naming and translation. EEG measures revealed significant interactions between Language and Stimulation on picture naming around 380 ms post-stimulus onset and Translation direction and Stimulation on translation around 530 ms post-stimulus onset. These effects suggest that L2 phonological retrieval and phoneme encoding are spatially and temporally segregated in the brain. We conclude that anodal-tDCS stimulation has an effect at a neural level on phonological processes and, critically, that DLPFC-mediated activation is a constraint on language production specifically in L2.

Dementia of Alzheimer Type can Alter both Languages in Late Bilinguals

Introduction Behavioral, clinical and neuroimaging evidence indicate that the first (L1) and the second language (L2) of bilingual individuals are supported by partly overlapping anatomo-functional pathways. While in the specific cases of patients suffering from cortical neurodegenerative diseases neuropsychological models predict that, in late bilinguals, L2 could be more impaired than L2, clinical data so far failed to demonstrate such dissociation. Method To address this question, we compared language performance in different tasks of oral and comprehension (semantic and syntactic) and production (naming, repetition, and fluency) in L1 and L2 in a group of 13 late proficient bilinguals with dementia of Alzheimer type (DAT) with 12 healthy late bilinguals matched in several demographic and linguistic factors including education level, age of L2 acquisition and immersion. Results Two-way mixed repeated-measure ANOVAs with factors Language and Group reveal main effects of Group (P<0.05) in all language tasks except for the counting and the sentence repetition tasks, indicating that DAT impact all aspects of language. Our analyses did not reveal any Group X Language interaction, suggesting that DAT impacted similarly on both languages. Conclusion Our results suggest that, like in stroke patients, neurodegenerative disease affects in a parallel manner oral language in L1 and L2, particularly at level of semantic, lexical and syntactic level of processing. These results do not support divergent models of bilingual brain representations, but rather argue for a substantially shared L1 and L2 network in late bilinguals.