ERP correlates of word production before and after stroke in an aphasic patient

No abstract available

Time course of evoked-potential changes in different forms of anomia in aphasia

No abstract available

Brain plasticity in aphasic patients: Intra- and inter-hemispheric reorganisation of the whole linguistic network probed by N150 and N350 components

The present study examined linguistic plastic reorganization of language through Evoked Potentials in a group of 17 non-fluent aphasic patients who had suffered left perisylvian focal lesions, and showed a good linguistic recovery. Language reorganisation was probed with three linguistic tasks (Phonological, Semantic, Orthographic), the early word recognition potential (N150) and the later phonological-related component (N350). Results showed the typical left-lateralised posterior N150 in healthy controls (source: left Fusiform Gyrus), that was bilateral (Semantic) or right sided (Phonological task) in patients (sources: right Inferior/Middle Temporal and Fusiform Gyri). As regards N350, controls revealed different intra- and inter-hemispheric linguistic activation across linguistic tasks, whereas patients exhibited greater activity in left intact sites, anterior and posterior to the damaged area, in all tasks (sources: Superior Frontal Gyri). A comprehensive neurofunctional model is presented, describing how complete intra- and inter-hemispheric reorganisation of the linguistic networks occurs after aphasic damage in the strategically dominant left perisylvian linguistic centres

The protective influence of bilingualism on the recovery of phonological input processing in aphasia after stroke

Language-related potentials are increasingly used to objectify (mal)adaptive neuroplasticity in stroke-related aphasia recovery. Using preattentive [mismatch negativity (MMN)] and attentive (P300) phonologically related paradigms, neuroplasticity in sensory memory and cognitive functioning underlying phonological processing can be investigated. In aphasic patients, MMN amplitudes are generally reduced for speech sounds with a topographic source distribution in the right hemisphere. For P300 amplitudes and latencies, both normal and abnormal results have been reported. The current study investigates the preattentive and attentive phonological discrimination ability in 17 aphasic patients (6 monolinguals and 11 bilinguals, aged 41-71 years) at two timepoints during aphasia recovery. Between the two timepoints, a significant improvement of behavioral language performance in both languages is observed in all patients with the MMN latency at timepoint 1 as a predictive factor for aphasia recovery. In contrast to monolinguals, bilingual aphasic patients have a higher probability to improve their processing speed during rehabilitation, resulting in a shortening of the MMN latency over time, which sometimes progresses toward the normative values

Treatment of non-fluent aphasia through melody, rhythm and formulaic language

Left-hemisphere stroke patients often suffer a profound loss of spontaneous speech — known as non-fluent aphasia. Yet, many patients are still able to sing entire pieces of text fluently. This striking finding has inspired mainly two research questions. If the experimental design focuses on one point in time (cross section), one may ask whether or not singing facilitates speech production in aphasic patients. If the design focuses on changes over several points in time (longitudinal section), one may ask whether or not singing qualifies as a therapy to aid recovery from aphasia. The present work addresses both of these questions based on two separate experiments. A cross-sectional experiment investigated the relative effects of melody, rhythm, and lyric type on speech production in seventeen patients with non-fluent aphasia. The experiment controlled for vocal frequency variability, pitch accuracy, rhythmicity, syllable duration, phonetic complexity and other influences, such as learning effects and the acoustic setting. Contrary to earlier reports, the cross-sectional results suggest that singing may not benefit speech production in non-fluent aphasic patients over and above rhythmic speech. Previous divergent findings could very likely be due to affects from the acoustic setting, insufficient control for syllable duration, and language-specific stress patterns. However, the data reported here indicate that rhythmic pacing may be crucial, particularly for patients with lesions including the basal ganglia. Overall, basal ganglia lesions accounted for more than fifty percent of the variance related to rhythmicity. The findings suggest that benefits typically attributed to singing in the past may actually have their roots in rhythm. Moreover, the results demonstrate that lyric type may have a profound impact on speech production in non-fluent aphasic patients. Among the studied patients, lyric familiarity and formulaic language appeared to strongly mediate speech production, regardless of whether patients were singing or speaking rhythmically. Lyric familiarity and formulaic language may therefore help to explain effects that have, up until now, been presumed to result from singing. A longitudinal experiment investigated the relative long-term effects of melody and rhythm on the recovery of formulaic and non-formulaic speech. Fifteen patients with chronic non-fluent aphasia underwent either singing therapy, rhythmic therapy, or standard speech therapy. The experiment controlled for vocal frequency variability, phonatory quality, pitch accuracy, syllable duration, phonetic complexity and other influences, such as the acoustic setting and learning effects induced by the testing itself. The longitudinal results suggest that singing and rhythmic speech may be similarly effective in the treatment of non-fluent aphasia. Both singing and rhythmic therapy patients made good progress in the production of common, formulaic phrases — known to be supported by right corticostriatal brain areas. This progress occurred at an early stage of both therapies and was stable over time. Moreover, relatives of the patients reported that they were using a fixed number of formulaic phrases successfully in communicative contexts. Independent of whether patients had received singing or rhythmic therapy, they were able to easily switch between singing and rhythmic speech at any time. Conversely, patients receiving standard speech therapy made less progress in the production of formulaic phrases. They did, however, improve their production of unrehearsed, non-formulaic utterances, in contrast to singing and rhythmic therapy patients, who did not. In light of these results, it may be worth considering the combined use of standard speech therapy and the training of formulaic phrases, whether sung or rhythmically spoken. This combination may yield better results for speech recovery than either therapy alone. Overall, treatment and lyric type accounted for about ninety percent of the variance related to speech recovery in the data reported here. The present work delivers three main results. First, it may not be singing itself that aids speech production and speech recovery in non-fluent aphasic patients, but rhythm and lyric type. Second, the findings may challenge the view that singing causes a transfer of language function from the left to the right hemisphere. Moving beyond this left-right hemisphere dichotomy, the current results are consistent with the idea that rhythmic pacing may partly bypass corticostriatal damage. Third, the data support the claim that non-formulaic utterances and formulaic phrases rely on different neural mechanisms, suggesting a two-path model of speech recovery. Standard speech therapy focusing on non-formulaic, propositional utterances may engage, in particular, left perilesional brain regions, while training of formulaic phrases may open new ways of tapping into right-hemisphere language resources — even without singing

Language Deficits Assessed in an Aphasic Patient

Aphasia is often the result of traumatic brain injury, stroke, brain disease or infection that has affected the language control centers of the brain. Here, event related potentials (ERPs) were used to explore differences in brain activation between an aphasic patient and controls in response to specific stimuli. Previous research indicates that aphasics have a dampened ERP response to different violations of sentence structure. Our aphasic patient, WD, and seven undergraduate controls were studied in three language processing tasks while continuous electroencephalography (EEG) was recorded. First, participants listened to a series of audio sentences that contained subject verb violations. Next, participants listened to a series of audio sentences that contained context mismatches. Finally, participants completed fill in the blank sentences by voicing the completing word aloud. The P600, N400, and P300 ERP components were examined in brain areas of interest, particularly in frontal regions. WD showed quantitative and qualitative ERP changes in all tasks revealing an atypical neural response despite typical behavioral performance

Semantic radical consistency and character transparency effects in Chinese: an ERP study

BACKGROUND: This event-related potential (ERP) study aims to investigate the representation and temporal dynamics of Chinese orthography-to-semantics mappings by simultaneously manipulating character transparency and semantic radical consistency. Character components, referred to as radicals, make up the building blocks used dur...postprin