Resting-state Spontaneous Brain Activity And The Rehabilitation Mechanism Of Language Function In Aphasia

Aphasia referred to the loss or impairment of language caused by brain damage,about 21%-38%of acute stroke survivors suffer from aphasia,which has a large impact on the quality of life.However,the characteristics of spontaneous brain activity in aphasia patients are not well characterized.Furthermore,little is known regarding the neural mechanisms of the functional recovery of language that underlie rehabilitation treatments in aphasia.The aims of this study were to investigate resting-state spontaneous brain activity in aphasic patients and the neural mechanisms underlying repetitive Transcranial Magnetic Stimulation(rTMS)treatments based on functional magnetic resonance imaging(fMRI).In the first study,resting-state fMRI was used to investigate the changes in spontaneous brain activity in aphasic patients.We examined the alterations in regional homogeneity(ReHo),amplitude of low-frequency fluctuation(ALFF)values and functional connectivity(FC)in 13 aphasic patients,all having suffered a stroke in the left hemisphere,compared to 13 aged-and sex-matched healthy controls.The results showed that compared with controls,aphasic patients exhibited ReHo,ALFF and FC difference in similar areas,and mainly located in the language processing network,and the activity in right hemisphere was enhanced and in the left hemisphere was reduced.In addition,the FC between the right frontal cortex and the corpus callosum is enhanced in aphasia,and the corpus callosum was involved in interaction of the two hemispheres.Our data indicated that it may be due to the disinhibition effect of the left dominant hemisphere through the corpus callosum,and the compensatory function of the right hemisphere of aphasic patients.In the second study,our aim was to investigate the mechanisms that underlay high-frequency rTMS treatments in an aphasic patient.The language behavior evaluation,fIRI and diffusion tensor imaging(DTI)data were respectively used to investigate the performance of language behavior,the functional and microstructural changes pre-and post-treatment.The results demonstrated that the patient’s language ability had actually improved.The fMRI results indicated a more focused activation pattern and showed significant activation in the left dominant hemisphere than right,especially perilesional areas,post-treatment compared with pre-treatment.Moreover,the fractional anisotropy increased in the left superior temporal gyrus,which comprises an important area involved in language processing.Our findings suggested that rTMS improved the speech-language ability of this aphasic patient,and induced language activation pattern changes and increased the white matter integrity.This may be due to rTMS enhancing the cerebral functional and microstructural reorganization of left dominant hemisphere.