Resting-State Functional Magnetic Resonance Imaging Connectivity Between Semantic and Phonological Regions of Interest May Inform Language Targets in Aphasia

Abstract

Purpose Brain imaging has provided puzzle pieces in the understanding of language. In neurologically healthy populations, the structure of certain brain regions is associated with particular language functions (e.g., semantics, phonology). In studies on focal brain damage, certain brain regions or connections are considered sufficient or necessary for a given language function. However, few of these account for the effects of lesioned tissue on the “functional” dynamics of the brain for language processing. Here, functional connectivity (FC) among semantic–phonological regions of interest (ROIs) is assessed to fill a gap in our understanding about the neural substrates of impaired language and whether connectivity strength can predict language performance on a clinical tool in individuals with aphasia. Method Clinical assessment of language, using the Western Aphasia Battery–Revised, and resting-state functional magnetic resonance imaging data were obtained for 30 individuals with chronic aphasia secondary to left-hemisphere stroke and 18 age-matched healthy controls. FC between bilateral ROIs was contrasted by group and used to predict Western Aphasia Battery–Revised scores. Results Network coherence was observed in healthy controls and participants with stroke. The left–right premotor cortex connection was stronger in healthy controls, as reported by New et al. (2015) in the same data set. FC of (a) connections between temporal regions, in the left hemisphere and bilaterally, predicted lexical–semantic processing for auditory comprehension and (b) ipsilateral connections between temporal and frontal regions in both hemispheres predicted access to semantic–phonological representations and processing for verbal production. Conclusions Network connectivity of brain regions associated with semantic–phonological processing is predictive of language performance in poststroke aphasia. The most predictive connections involved right-hemisphere ROIs—particularly those for which structural adaptions are known to associate with recovered word retrieval performance. Predictions may be made, based on these findings, about which connections have potential as targets for neuroplastic functional changes with intervention in aphasia. Supplemental Material https://doi.org/10.23641/asha.12735785

Association of ictal aphasia with hypoperfusion in language areas in temporal lobe epilepsy patients

“…Ictal aphasia associated with this location has been reported 13 highlighting its potential role as a key node for language. In the present report, additional data is provided supporting the existence of a language network connecting Wernicke's area, Broca's area, and the basal temporal region, as postulated in connectivity studies 14 . These findings may question the prevalent hypothesis of a basal temporal area specific to semantic aspects of language, and highlight the complexity of a network with cortical and subcortical hubs, and both excitation and inhibition phenomena.…”

“…In the present report, additional data is provided supporting the existence of a language network connecting Wernicke's area, Broca's area, and the basal temporal region, as postulated in connectivity studies. 14 These findings may question the prevalent hypothesis of a basal temporal area specific to semantic aspects of language, and highlight the complexity of a network with cortical and subcortical hubs, and both excitation and inhibition phenomena. Moreover, an extended network must be involved to explain a more widespread deactivation response as shown in Patient 3.…”

Longitudinal changes in functional connectivity in speech motor networks in apraxia of speech after stroke

“…To compensate, an increased activation of the right aINS may also occur ( 36 ). Ramage et al ( 65 ) used the same data set as New et al to study a network of brain regions considered as key regions for semantic and phonological processing in post stroke aphasia. Their results indicated that ipsilateral connections between temporal and frontal regions in both the left and the right hemisphere could predict access to semantic and phonological representations that serve as a basis for speech production.…”

Exploring the functional connectivity characteristics of brain networks in post-stroke patients with global aphasia: a healthy control based resting-state fMRI study

“…The auditory information is first transmitted to the temporalparietal-occipital association cortex, of which the AG is the center, and then transmitted to the Wernicke's area. Ramage et al (52) demonstrated that connections between the left AG and left ITG was the only significant predictor of auditory comprehension scores in chronic aphasia patients. The occipital lobe is thought to be mainly related to visual information integration.…”