Functional brain network abnormalities during verbal working memory performance in adolescents and young adults with dyslexia.
Behavioral and functional neuroimaging studies indicate deficits in verbal working memory (WM) and frontoparietal dysfunction in individuals with dyslexia. Additionally, structural brain abnormalities in dyslexics suggest a dysconnectivity of brain regions associated with phonological processing. However, little is known about the functional neuroanatomy underlying cognitive dysfunction in dyslexia. In this study, functional magnetic resonance imaging and multivariate analytic techniques were used to investigate patterns of functional connectivity during a verbal WM task in individuals with dyslexia (n=12) and control subjects (n=13). Dyslexics were not significantly slower than controls; however, they were less accurate with increasing WM demand. Independent component analysis identified 18 independent components (ICs) among which two ICs were selected for further analyses. These ICs included functional networks which were positively correlated with the delay period of the activation task in both healthy controls and dyslexics. Connectivity abnormalities in dyslexics were detected within both networks of interest: within a "phonological" left-lateralized prefrontal network, increased functional connectivity was found in left prefrontal and inferior parietal regions. Within an "executive" bilateral frontoparietal network, dyslexics showed a decreased connectivity pattern comprising bilateral dorsolateral prefrontal and posterior parietal regions, while increased connectivity was found in the left angular gyrus, the left hippocampal cortex and the right thalamus. The functional connectivity strength in the latter regions was associated with WM task accuracy and with the numbers of errors during a spelling test. These data suggest functional connectivity abnormalities in two spatiotemporally dissociable brain networks underlying WM dysfunction in individuals with dyslexia.
Department of Psychiatry and Psychotherapy III, University of Ulm, Leimgrubenweg 12-14, 89075 Ulm, Germany. christian.wolf@uni-ulm.de
Robert Christian
RC
Wolf
Fabio
F
Sambataro
Christina
C
Lohr
Claudia
C
Steinbrink
Claudia
C
Martin
Nenad
N
Vasic
D000293:Adolescent; D001921:Brain / Q000033:anatomy & histology / Q000098:blood supply / Q000503:physiopathology; D001931:Brain Mapping; D004410:Dyslexia / Q000473:pathology* / Q000503:physiopathology*; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D008570:Memory, Short-Term / Q000502:physiology*; D009415:Nerve Net / Q000098:blood supply / Q000473:pathology / Q000503:physiopathology; D009434:Neural Pathways / Q000098:blood supply / Q000503:physiopathology; D009483:Neuropsychological Tests; D010100:Oxygen / Q000097:blood; D025341:Principal Component Analysis / Q000379:methods; D011930:Reaction Time / Q000502:physiology; D013223:Statistics as Topic; D014705:Verbal Behavior / Q000502:physiology*; D055815:Young Adult
D010100:Oxygen