Biomarkers of Neuroplasticity Improve Predictions of Aphasia Severity

EasyChair Preprint 6357

Abstract

Variability in aphasia has been associated with age, lesion size, and time post-stroke. However, predicting language recovery remains imprecise. We examine whether genetic and neuorphysiologcail biomarkers of neuroplasticity improve abilities to predict language recovery, measured by Western Aphasia Battery-Aphasia Quotient (WAB-AQ). We investigate whether predictions are improved by examining interactions between genetic polymorphism (brain-derived neurotropic factor, BDNF) and neurophysiological indicators of plasticity– cortical excitability measured through motor-evoked potentials (MEPs) pre- and post-continuous theta burst stimulation (cTBS). We collected MEPs pre- and post-cTBS to motor cortex in 19 adults with chronic post-stroke aphasia. We evaluated the extent to which BDNF interacted with pre-cTBS cortical excitability, and cTBS-induced MEP-suppression to predict WAB-AQ. These were analyzed in a backward stepwise linear regression model, with additional predictors of age, lesion volume, and time post-stroke. While controlling for time post-stroke and lesion volume, BDNF genotype showed a main effect such that ValVal carriers showed better recovery than Met carriers (β=22.68, p<0.001). Furthermore, BDNF interacted with age at stroke, baseline MEP, and change in MEP. Increased age was associated with lower WAB-AQ for both groups, but had a stronger effect for ValVal (β=-1.17, p<0.001) than Met carriers (β=-0.81, p<0.001). Cortical excitability was positively associated with WAB-AQ for ValVal carriers (β=6.48, p<0.001), but negatively associated for Met carriers (β=-8.49, p<0.001). Met carriers with lower WAB-AQ showed increased paradoxical responses to cTBS (β=-8.29, p<0.001), whereas cTBS-induced MEP changes were not associated with variability in WAB-AQ for ValVal carriers (β=0.30, p=0.59). These findings show how measures of neuroplasticity improve predictions of language recovery.

Keyphrases: Motor Evoked Potentials, Neuroplasticity, Non-invasive brain stimulation, aphasia severity, biomarkers, genotypes, language recovery

@booklet{EasyChair:6357,
  author    = {Haley Dresang and Denise Y. Harvey and Roy Hamilton},
  title     = {Biomarkers of Neuroplasticity Improve Predictions of Aphasia Severity},
  howpublished = {EasyChair Preprint 6357},
  year      = {EasyChair, 2021}}