TITLE:
Magnetoencephalography Coherence Source Imaging in Dyslexia: Activation of Working Memory Pathways
AUTHORS:
Alfred Mansour, Susan M. Bowyer, Annette E. Richard, John E. Moran, Laszlo A. Erdodi, Amy Olszewski, Lesley Pawluk, Daniel Jacobson, Kelly Vogt, Aimee M. Moore, Renée Lajiness-O’Neill
KEYWORDS:
Dyslexia, Reading Disorder, Learning Disorder, Magnetoencephalography, Functional Brain Imaging
JOURNAL NAME:
Psychology,
Vol.5 No.16,
October
31,
2014
ABSTRACT: This
study investigates the functional connectivity of neuronal networks critical
for working memory in individuals with dyslexia by means of
magnetoenchephalographic (MEG) coherence imaging. Individuals with dyslexia
showed an early onset of activation in anterior cortical regions (precentral
gyrus and the superior frontal gyrus), which differed from controls where
activation initiated in posterior cortical regions (supramarginal gyrus and
superior temporal gyrus). Further, individuals with dyslexia showed lower brain
activity in the right superior temporal gyrus and right middle temporal gyrus
than controls during a spatial working memory (SWM) task. In contrast, during a
verbal working memory (VWM) task, individuals with dyslexia showed lower
activity in the right insular cortex and right superior temporal gyrus and
higher, likely compensatory, activity in the right fusiform gyrus, left
parahippocampal gyrus, and left precentral gyrus. When performing a SWM task,
individuals with dyslexia showed significantly lower coherent activity and
synchronization in 1) right frontal connectivity, 2) right fronto-temporal
connectivity, 3) left and right frontal connectivity, 4) left temporal and
right frontal connectivity, and 5) left occipital and right frontal
connectivity. MEG coherence source imaging (CSI) by frequency bands showed
lower mean coherence values in individuals with dyslexia compared to controls
for each frequency range during the SWM task. In contrast, during the VWM task,
individuals with dyslexia showed higher coherent low frequency (3 - 15 Hz) and
lower coherent high frequency (30 - 45 Hz) synchronization than control
subjects. Logistic regression of coherent activity by group membership was
significant, with an overall predictive
success of 84.4% (88.9% for controls and 77.8% for dyslexia). Coherence between
the right lateral orbitofrontal and middle orbitofrontal gyri pair
substantially contributed to group membership. The results suggest a pattern of
aberrant connectivity as evidenced by the early onset and reliance on prefrontal
cortical areas, the differential activation of fronto-temporal brain systems,
and an altered pattern of functional connectivity in the frontotemporal
pathways mediating these behaviors.