Ana Inés Ansaldo

Training-induced brain remapping in chronic aphasia: a pilot study.

Background. The neural correlates of training-induced improvements of cognitive functions after brain damage remain still scarcely understood. In the specific case of aphasia, although several investigations have addressed the issue of the neural substrates of functional recovery, only a few studies have attempted to assess the impact of language training on the damaged brain. Aims. The main goal of this study was to examine the neurobiological correlates of improved picture-naming performance in 2 aphasic patients who received intensive and specific training for a chronic and severe phonological anomia. Methods. In both participants, picture-naming performance was assessed before and after phonological cueing training. Training-induced changes in patients’ performance were correlated to brain activity patterns as revealed by pre- and post-training event-related functional magnetic resonance imaging scanning. Results. Training-induced improvement was observed concurrently with changes in the brain activation patterns. Better performance was observed in the patient with the smaller lesion, partially sparing Broca’s area, who showed a left perilesional reactivation. Conversely, the patient with complete destruction of Broca’s area showed a posttraining activation in the right mirror frontal region. Conclusions. The results show that, even in the chronic stage, phonological strategies may improve impaired naming and induce cerebral reorganization.

Anomia training and brain stimulation in chronic aphasia

Recent studies have reported enhanced performance on language tasks induced by non-invasive brain stimulation, i.e., repetitive transcranial magnetic stimulation (rTMS), or transcranial direct current stimulation (tDCS), in patients with aphasia due to stroke or Alzheimers disease (AD). The first part of this article reviews brain stimulation studies related to language recovery in aphasic patients. The second part reports results from a pilot study with three chronic stroke patients who had non-fluent aphasia, where real or placebo rTMS was immediately followed by 25 minutes of individualised speech therapy. Real rTMS consisted of high-frequency rTMS over the left dorsolateral prefrontal cortex (BA 8/9) for 25 minutes. Each patient underwent a total of four weeks of intervention. P1 underwent four weeks of real rTMS (5 days/week) where individualised speech therapy was provided for 25 minutes immediately following each rTMS session. P2 and P3 each underwent two weeks of placebo rTMS, followed immediately by individualised speech therapy; then two weeks of real rTMS, followed immediately by individualised speech therapy. Assessments took place at 2, 4, 12, 24 and 48 weeks post-entry/baseline testing. Relative to entry/baseline testing, a significant improvement in object naming was observed at all testing times, from two weeks post-intervention in real rTMS plus speech therapy, or placebo rTMS plus speech therapy. Our findings suggest beneficial effects of targeted behavioural training in combination with brain stimulation in chronic aphasic patients. However, further work is required in order to verify whether optimal combination parameters (rTMS alone or speech therapy alone) and length of rTMS treatment may be found.

The complementary role of the cerebral hemispheres in recovery from aphasia after stroke: A critical review of literature

Abstract Objectives: To review the literature on the specific role of the right cerebral hemisphere during recovery from aphasia in order to address the lack of consensus among authors. To derive a theoretical model reconciling the controversial findings in the literature. Methods: Initial PubMed, MEDLINE (1946 to 5 May 2012) and PsycINFO (1806 to first week June 2012) searches on recovery mechanisms from aphasia, whether treatment-related or not, retrieved a total of 35 English language articles. Articles, cross-referenced in this initial set were also reviewed if they met the inclusion criteria, thus resulting in a total of 42 articles included in this review. Main outcomes: Recruitment of the right hemisphere during recovery from aphasia can be effective if it occurs during a critical time window post-stroke. The recruitment’s effectiveness will depend on the lesion’s location, extent and permanence. Preservation of core language processing areas will generate minimal right hemisphere recruitment and vice versa. Some experimental studies seem to suggest that the improvement linked to a particular hemisphere can be modulated by specific therapy methods. Conclusion: The specific conditions in which effective right recruitment takes place may have important implications for rehabilitation treatment. These findings could lead to improved recovery in people suffering from aphasia. However, more research with non-invasive brain stimulation is needed.

Therapy-induced neuroplasticity in chronic aphasia

Research on the neural substrate of aphasia recovery has consistently increased since the advent of functional neuroimaging. The evidence from therapy-induced aphasia recovery studies shows that better recovery results from the reactivation of left hemisphere function; still, the specific left hemisphere key areas that sign successful outcome with a specific therapy approach remain to be identified. Nine participants suffering from aphasia received brief and intensive therapy with Semantic Feature Analysis (SFA). Behavioural and neuroimaging data during overt picture naming were obtained prior to and after therapy. This paper reports on a group of participants having benefited from SFA, and two distinct patterns of improvement. Correlational analysis showed that differences in outcome were not related to lesion size, but were negatively correlated with damage to Brocas area (BA45). Moreover, a group analysis showed that therapy-induced recovery following SFA was characterized by (a) a significant correlation between improvement and activation in the left precentral gyrus (BA4/6) before therapy, and (b) the recruitment of the left inferior parietal lobule, an area known for its role in semantic integration, following therapy with SFA. Individual fMRI analyses showed that although adaptive brain plasticity appeared to operate differently in each patient, best responders to SFA therapy recruited less areas after training compared to participants having shown less recovery who showed a larger number of activated areas sustaining recovery. The results of the present study suggest that a significant activation of BA4/6 could indicate the use of SFA to achieve successful outcome. Also our results suggest that greater SFA improvement in chronic aphasia is associated with recruitment of areas in the left hemisphere.

The neural correlates of semantic feature analysis in chronic aphasia: discordant patterns according to the etiology.

This event-related functional magnetic resonance imaging (fMRI) study reports on the impact of semantic feature analysis (SFA) therapy on the neural substrate sustaining the recovery from severe anomia in two patients: one participant was diagnosed with primary progressive aphasia (PPA) 2 years before this study; the other participant acquired aphasia 8 years before this study. The participant with PPA showed severe progressive nonfluent aphasia (PNFA), the language profile being similar to a Brocas aphasia; the stroke patient presented with Brocas aphasia and a severe apraxia of speech (AOS). To examine the neural substrate allowing for recovery, both patients received brief and intensive therapy with SFA; behavioral and event-related (ER)-fMRI measures during oral picture naming were obtained pre- and post-therapy. Both patients benefitted from SFA to improve their naming performance. Functional MRI performances on trained and correct pretraining items were contrasted. Adaptive brain plasticity appeared to operate differently in each patient, despite the similarity of naming recovery profiles.

Default-Mode Network Functional Connectivity in Aphasia: Therapy-Induced Neuroplasticity.

Previous research on participants with aphasia has mainly been based on standard functional neuroimaging analysis. Recent studies have shown that functional connectivity analysis can detect compensatory activity, not revealed by standard analysis. Little is known, however, about the default-mode network in aphasia. In the current study, we studied changes in the default-mode network in subjects with aphasia who underwent semantic feature analysis therapy. We studied nine participants with chronic aphasia and compared them to 10 control participants. For the first time, we identified the default-mode network using spatial independent component analysis, in participants with aphasia. Intensive therapy improved integration in the posterior areas of the default-mode network concurrent with language improvement. Correlations between integration and improvement did not reach significance, but the trend suggests that pre-therapy integration of the default-mode network may predict therapy outcomes. Functional connectivity allows a better understanding of the impact of semantic feature analysis in aphasia.

Clinical note: acquired pragmatic impairments and aphasia.

Recent advances in the field of communication sciences have led to the description of acquired communication disorders affecting pragmatic skills in patients with brain damage. The present article discusses the impact of such findings on the clinical concept of aphasia. Through reference to a number of articles contained in this Special Issue, it must be reiterated that pragmatic and other linguistic components of communication abilites are two sides of a same coin-that of language-and intimately interrelated. It is also argued that the difference between traditional (e.g., syntax) and pragmatic components of language cannot be explained in simple terms such as the former being subserved only by linguistic processes and the latter by other cognitive processes. Pragmatic components are thus to be considered as part of language. The evolution of the concept of language has a direct impact on the clinical concept of aphasia. Indeed, if aphasia corresponds to an acquired impairment of language, then pragmatic impairments must be considered part of aphasia. The inclusion of pragmatic impairments in the concept of aphasia does not hold only when they occur within the frame of classic types of aphasia, but also when they occur in isolation. Consequently, a new type of aphasia-pragmatic aphasia-should be considered and defined in order to describe the clinical condition of those individuals suffering from acquired pragmatic disorders as those reported among right-hemisphere-damaged right-handers. It is concluded that the recent evolution around the concept of language should be followed by an evolution of the concept of aphasia per se.

Brain activation and lexical learning: The impact of learning phase and word type

This study investigated the neural correlates of second-language lexical acquisition in terms of learning phase and word type. Ten French-speaking participants learned 80 Spanish words-40 cognates, 40 non-cognates-by means of a computer program. The learning process included the early learning phase, which comprised 5 days, and the consolidation phase, which lasted 2 weeks. After each phase, participants performed an overt naming task during an er-fMRI scan. Naming accuracy was better for cognates during the early learning phase only. However, cognates were named faster than non-cognates during both phases. The early learning phase was characterized by activations in the left iFG and Brocas area, which were associated with effortful lexical retrieval and phonological processing, respectively. Further, the activation in the left ACC and DLPFC suggested that monitoring may be involved during the early phases of lexical learning. During the consolidation phase, the activation in the left premotor cortex, the right supramarginal gyrus and the cerebellum indicated that articulatory planning may contribute to the consolidation of second-language phonetic representations. No dissociation between word type and learning phase could be supported. However, a Fisher r-to-z test showed that successful cognate retrieval was associated with activations in Brocas area, which could reflect the adaptation of known L1 phonological sequences. Moreover, successful retrieval of non-cognates was associated with activity in the anterior-medial left fusiform and right posterior cingulate cortices, suggesting that their successful retrieval may rely upon the access to semantic and lexical information, and even on the greater likelihood of errors.

Model‐driven intervention in bilingual aphasia: Evidence from a case of pathological language mixing

Background: Speech‐language pathologists are meeting an increasing number of bilingual clients. This poses a special challenge to clinical practice, given that bilingualism adds to the complexity of aphasia patterns and clinical decisions must be made accordingly. One question that has come to the attention of clinical aphasiologists is that of the language in which therapy should be administered. This issue becomes particularly relevant in cases of involuntary language switching, when choosing between L1 and L2 implies inhibiting one of the languages. Models of lexical selection in bilingual people offer a rationale for language choice based on the specificities of bilingual aphasia within each client. Aims: To provide evidence for model‐based intervention in bilingual aphasia, particularly in cases of pathological language switching. Methods & Procedures: This paper reports a model‐driven intervention in a case of involuntary language switching following aphasia in a Spanish–English bilingual client. Outcomes & Results: Intervention tailored to the clients strengths resulted in improved communication skills thanks to the implementation of a self‐regulated strategy to overcome involuntary language switching. Conclusions: Model‐driven descriptions of bilingual aphasia contribute to efficient intervention by identifying therapy approaches that take account of each clients language abilities. Further, clinical data analysed within models of bilingual language processing can provide evidence for dissociations between components of the bilingual lexical system.

The contribution of the right cerebral hemisphere to the recovery from aphasia: a single longitudinal case study

We examined the role of the right cerebral hemisphere in the recovery from aphasia of HJ, a 50-year-old right-handed and unilingual man who suffered from severe aphasia caused by an extensive left hemisphere (LH) lesion. He was followed-up over 10 months at 4-month intervals, with a lateralized lexical decision task (LDT), an attentional task, and a language battery. Testing started when HJ was 2 months poststroke. In the LDT, words were presented to central vision or lateralized to the left or right visual hemifield. At each test period, we examined the effect of the degree of imageability (high vs. low), and the grammatical class (noun vs. verb) of the targets on HJs response times and error rates, with left visual field, right visual field, and central vision presentations. The results of the experiment showed that the pattern obtained with the LDT could not be accounted for by fluctuations in attention. There was an interaction of grammatical class with degree of imageability with left visual field displays only. The right hemisphere (RH) was faster with high-imageability words than with low-imageability words, regardless of their grammatical class. There was also an overall RH advantage on response times at 2 and 6 months after onset. This RH predominance coincided with a major recovery of language comprehension and the observation of semantic paralexias, while no major change in language expression was observed at that point. Ten months after onset, the pattern of lateralization changed, and response times for the LDT with either presentation site were equivalent. This LH improvement coincided with some recovery of language expression at the single-word level. The results of this study suggest that, in cases of severe aphasia caused by extensive LH lesions, the RH may play an important role in the recovery process. Furthermore, these results show that the contribution of the two cerebral hemispheres to recovery may vary overtime and affect specific aspects of language.