Semantic Processing in Bilingual Aphasia: Evidence of Language Dependency

French Phonological Component Analysis and aphasia recovery: A bilingual perspective on behavioral and structural data

Studies show bilingualism entails an advantage in cognitive control tasks. There is evidence of a bilingual advantage in the context of aphasia, resulting in better cognitive outcomes and recovery in bilingual persons with aphasia compared to monolingual peers. This bilingual advantage also results in structural changes in the right hemisphere gray matter. Very few studies have examined the so-called bilingual advantage by reference to specific anomia therapy efficacy. This study aims to compare the effect of French-Phonological Component Analysis (Fr-PCA) in monolinguals and bilingual persons with aphasia, both at the linguistic and cognitive control level, and to examine the structural impact of left hemisphere lesion location and right hemisphere structural data. Eight participants with chronic aphasia received Fr-PCA for a total of 15 h over 5 weeks. The results showed improved accuracy for treated words and generalization to untreated items and discourse in both groups, and improved Flanker task performance for some participants. Bilingual participants improved more than monolinguals for picture-naming tasks and narrative discourse. Damage to the left postcentral gyrus and the middle frontal gyrus was associated with less therapy-induced improvement. Additionally, left hemisphere damage to the inferior parietal gyrus and postcentral gyrus was associated with reduced cognitive control pre-therapy. Undamaged right hemisphere cortical thicknesses were significantly different between groups; the inferior frontal gyrus and the middle frontal gyrus were greater for the bilingual participants and correlated with cognitive control skills. These results suggest a bilingual advantage in anomia recovery following Fr-PCA, potentially resulting from enhanced cognitive control abilities that could be supported by right hemisphere neural reserve.

Distinguishing semantic control and phonological control and their role in aphasic deficits: A task switching investigation

People use cognitive control across many contexts in daily life, yet it remains unclear how cognitive control is used in contexts involving language. Distinguishing language-specific cognitive control components may be critical to understanding aphasia, which can co-occur with cognitive control deficits. For example, deficits in control of semantic representations (i.e., semantic control), are thought to contribute to semantic deficits in aphasia. Conversely, little is known about control of phonological representations (i.e., phonological control) in aphasia. We developed a switching task to investigate semantic and phonological control in 32 left hemisphere stroke survivors with aphasia and 37 matched controls. We found that phonological and semantic control were related, but dissociate in the presence of switching demands. People with aphasia exhibited group-wise impairment at phonological control, although individual impairments were subtle except in one case. Several individuals with aphasia exhibited frank semantic control impairments, and these individuals had relative deficits on other semantic tasks. The present findings distinguish semantic control from phonological control, and confirm that semantic control impairments contribute to semantic deficits in aphasia.

Evaluation of the Potential of Automatic Naming Latency Detection for Different Initial Phonemes during Picture Naming Task

Naming latency (NL) represents the speech onset time after the presentation of an image. We recently developed an extended threshold-based algorithm for automatic NL (aNL) detection considering the envelope of the speech wave. The present study aims at exploring the influence of different manners (e.g., "m" and "p") and positions (e.g., "t" and "p") of articulation on the differences between manual NL (mNL) and aNL detection.Speech samples were collected from 123 healthy participants. They named 118 pictures in German, including different initial phonemes. NLs were manually (Praat, waveform and spectrogram) and automatically (developed algorithm) determined. To investigate the accuracy of automatic detections, correlations between mNLs and aNLs were analyzed for different initial phonemes.ANLs and mNLs showed a strong positive correlation and similar tendencies in initial phoneme groups. ANL mean values were shorter than the ones of mNLs. Nasal sounds (e.g., /m/) showed the largest and those for fricatives (e.g., /s/) the smallest difference. However, in fricatives, 39% of NLs were detected later by automatic detections than by manual detections, which led to a reduced mean difference with mNLs. The signal energy of the initial phonemes, i.e., if they are voiced or voiceless, influences the form of the speech envelope: initial high signal energy is often responsible for an early detection by the algorithm.Our study provides evidence of a similar tendency in mNL and aNL according to different positions of articulation in each initial phoneme group. ANLs are highly sensitive to detection of speech onsets across different initial phonemes. The dependency of the NL differences on the initial phonemes will lose importance during progress evaluations in aphasia patients if the relative changes for each picture are considered separately. Nevertheless, the algorithm will be further optimized by adapting its parameters for each initial phoneme group individually.Clinical Relevance- This underlines the feasibility to use automatic naming latency detection for the evaluation of patients with aphasia in a clinical setting as well as for practices at home during picture naming.

Aphasia in Multilingual Patients

PURPOSE OF REVIEW

We summarize recent published work concerning assessment and treatment of aphasia in bilingual and multilingual people and review current related models of treatment outcomes. As well, we discuss studies that address the recently debated topic of cognitive processes in bilingual individuals with aphasia, with a focus on the effects of bilingualism on aphasia recovery and its potential protective effects.

RECENT FINDINGS

Providing assessment and treatment tools that best serve multilingual individuals with aphasia and unpacking the variables and mechanisms that underlie response to treatment have emerged as goals of several recent studies. Additionally, while findings are still contradictory, some empirical studies reported that aphasia may manifest less severely in multilingual individuals and may improve faster compared to in monolingual counterparts. The findings of recent studies with the focus of aphasia in multilingual individuals are crucial to understanding theoretical and clinical aspects of brain-related language impairment in multilingual people and to the study of language representation and processing in the brain.

Understanding the human language processor: Neurobiology's insights into the human brain's semantic processing of information could inform education and therapies for language disorders

Brain imaging and research on bilinguals and patients with speech disorders is helping to unravel semantic processing - the way how the brain interprets and stores sentences and stories.

The Relationship between Language Control, Semantic Control and Nonverbal Control

The purpose of this study was to examine the relationship between language control, semantic control, and nonverbal control in bilingual aphasia. Twelve bilingual adults with aphasia (BPWA) and 20 age-matched bilingual adults (AMBA) completed a language control task, semantic control task, and nonverbal control task, each designed to examine resistance to distractor interference. AMBA and BPWA exhibited significant effects of control on all tasks. To examine efficiency of control, conflict magnitudes for each task and group were analyzed. Findings revealed that AMBA exhibited larger conflict magnitudes on the semantic control task and nonverbal control task compared to the language control task, whereas BPWA exhibited no difference in conflict magnitudes between the language control task and semantic control task. Further analysis revealed that BPWA semantic control conflict magnitude was smaller than AMBA semantic control conflict magnitude. Taken together, these findings suggest that BPWA present with diminished effects of semantic control. In the final analysis, conflict magnitudes across tasks were correlated. For AMBA, semantic control and nonverbal control conflict magnitudes were significantly correlated, suggesting that these two types of control are related. For BPWA, language control and nonverbal control conflict magnitudes were significantly correlated; however, this finding may capture effects of domain general cognitive control as a function of increased cognitive load, rather than domain general cognitive control as a function of language control.

Variables and Mechanisms Affecting Response to Language Treatment in Multilingual People with Aphasia

BACKGROUND

Despite substantial literature exploring language treatment effects in multilingual people with aphasia (PWA), inconsistent results reported across studies make it difficult to draw firm conclusions.

METHODS

We highlight and illustrate variables that have been implicated in affecting cross-language treatment effects in multilingual PWA.

MAIN CONTRIBUTION

We argue that opposing effects of activation and inhibition across languages, influenced by pertinent variables, such as age of language acquisition, patterns of language use, and treatment-related factors, contribute to the complex picture that has emerged from current studies of treatment in multilingual PWA. We propose a new integrated model-Treatment Effects in Aphasia in Multilingual people (the TEAM model)-to capture this complexity.

Voluntary Language Switching in the Context of Bilingual Aphasia

As studies of bilingual language control (BLC) seek to explore the underpinnings of bilinguals’ abilities to juggle two languages, different types of language switching tasks have been used to uncover switching and mixing effects and thereby reveal what proactive and reactive control mechanisms are involved in language switching. Voluntary language switching tasks, where a bilingual participant can switch freely between their languages while naming, are being utilized more often due to their greater ecological validity compared to cued switching paradigms. Because this type of task had not yet been applied to language switching in bilingual patients, our study sought to explore voluntary switching in bilinguals with aphasia (BWAs) as well as in healthy bilinguals. In Experiment 1, we replicated previously reported results of switch costs and mixing benefits within our own bilingual population of Catalan-Spanish bilinguals. With Experiment 2, we compared both the performances of BWAs as a group and as individuals against control group performance. Results illustrated a complex picture of language control abilities, indicating varying degrees of association and dissociation between factors of BLC. Given the diversity of impairments in BWAs’ language control mechanisms, we highlight the need to examine BLC at the individual level and through the lens of theoretical cognitive control frameworks in order to further parse out how bilinguals regulate their language switching.

Active bilingualism delays the onset of mild cognitive impairment

Lifelong bilingualism may contribute to cognitive reserve (CR) in neurodegenerative diseases as shown by a delay of the age at symptom onset in bilinguals with Alzheimer's disease (AD) and Mild Cognitive Impairment (MCI). However, some studies have failed to show this bilingual advantage, suggesting that it might depend on the type and degree of bilingualism. In the present study, we tested the hypothesis that active bilingualism, defined as the continuous use of the two languages as opposed to second language exposition only, may protect against cognitive decline. Moreover, we investigated whether bilingualism as a CR factor may be explained by an advantage within the executive control (EC) system. To do so, we collected clinical measures (age at onset of cognitive symptoms, age at the first medical visit for cognitive impairments, and age at diagnosis) in patients with MCI and patients with AD with different degrees of language experience and usage of Catalan and Spanish. Additionally, all participants were tested on four EC tasks and one long-term memory recognition task. First, results from multiple regression analyses showed that active bilingualism was a significant predictor of delay in the age at onset for all the clinical measures in MCI, but not AD patients. Second, the effect of active bilingualism was independent of occupation, educational level and job attainment across the individuals' lifespan. Finally, although we did not find an effect of active bilingualism across all EC tasks, we did find an effect for conflict resolution. These results are discussed in the context of CR hypotheses, suggesting that compensatory mechanisms may play a role in protecting against cognitive decline.