Training-induced brain plasticity in aphasia

Abstract

It has long been a matter of debate whether recovery from aphasia after left perisylvian lesions is mediated by the preserved left hemispheric language zones or by the homologous right hemisphere regions. Using PET, we investigated the short-term changes in the cortical network involved in language comprehension during recovery from aphasia. In 12 consecutive measurements of regional cerebral blood flow (rCBF), four patients with Wernicke's aphasia, caused by a posterior left middle cerebral artery infarction, were tested with a language comprehension task. Comprehension was estimated directly after each scan with a modified version of the Token Test. In the interval between the scans, the patients participated in brief, intense language comprehension training. A significant improvement in performance was observed in all patients. We correlated changes in blood flow measured during the language comprehension task with the scores achieved in the Token Test. The regions which best correlated with the training-induced improvement in verbal comprehension were the posterior part of the right superior temporal gyrus and the left precuneus. This study supports the role of the right hemisphere in recovery from aphasia and demonstrates that the improvement in auditory comprehension induced by specific training is associated with functional brain reorganization.

Verbal language spontaneous recovery after ischemic stroke

“…In Brazil we still have difficulties in referring how important the speech treatment is for the reduction of recovery time. Our treated patients had spontaneous recovery in almost half the time of untreated ones, suggesting that the speech treatment maximizes recovery by promoting reorganization of cortical structures, according to the findings in studies that show speech and language therapy improves the patient's ability to use verbal skills along with non-verbal means to achieve an adequate situation of the social communication, and has beneficial effect when started early and with intense training 5,11,13 . In conclusion, the verbal language spontaneous recovery occurred in most patients at the outpatient ischemic stroke clinic with an average time of 6 months, and the language alteration most presented was in language expression.…”

“…The reorganization processes begin soon after the injury 23 . This cortical area reorganization related to language (temporal chain pre-existing frontal), consists in the activation of not injured areas in both hemispheres, but particularly the right hemisphere, that may be decisive for the recovery of the language function 11,[22][23][24][25] . In this sample only 15 patients were under speech treatment, different from what happens in the United States, where most of the patients who have language disturbs achieve specific treatment to improve the maximum recovery 26 .…”

“…A re-search showed that the Broca aphasia recovery involves the reorganization between the superior temporal gyrus, putamen and lower inferior temporal gyrus, while Wernicke aphasia involves the reorganization of temporal gyrus, supramarginal gyrus and lower parietal lobe 9 . Aphasic patients who suffered lesion in the brain' s language zones present a certain level of spontaneous recovery in almost all cases, due to neuronal plasticity, defined as any changes on cortical regions such as a the functional or morphological answer to environmental alterations or lesions' 10,11 . Studies have shown that the linguistic capacities recovery occurs faster on the early months after the stroke due to neuronal plasticity and also because few improvements are obtained after one year post stroke 12,13 .…”

Rehabilitation after Stroke

“…[20][21][22] Improvements in targeted language impairments have been associated with changes in activity in the cortical regions of the brain associated with language skills. 23,24 Self-Care and Functional Use of the Arm-Significant benefit is most often achieved among patients with moderate levels of disability as measured on functional scales, but not among those with the greatest disability. 25 For patients with hemiplegia, the initial functional training emphasizes compensatory strategies.…”

Functional magnetic resonance imaging: A review of methodological aspects and clinical applications

“…This functional improvement is accompanied by an increased excitability of primary motor cortex, due to a focal disinhibition (97)(98)(99) by transcranial magnetic stimulation. Musso et al (100) investigated correlations between the training-induced improvement of comprehension in stroke patients with chronic aphasia and changes in the activation pattern. They found a significant correlation of the improvement of function with an increase of activation over time in the right-sided homologue of Wernicke's area in the left hemisphere.…”