Magnetoencephalography Coherence Source Imaging in Dyslexia: Activation of Working Memory Pathways

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 * Corresponding author. A. Mansour et al. 1880 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.

Verbal Working Memory‐Balance program training alters the left fusiform gyrus resting‐state functional connectivity: A randomized clinical trial study on children with dyslexia

“…It has been reported that the bilateral fusiform areas activate in verbal WM tasks (Na et al, 2000), which might be due to a ventral visual pathway involved in the visual recognition of verbal stimuli (Büchel et al, 1998; Na et al, 2000). Another study revealed the hypoactivation of the fusiform gyrus in individuals with dyslexia when performing a verbal WM task (Mansour et al, 2014). Moreover, there is evidence that the bilateral fusiform gyri activate when performing active balance and ankle plantar/dorsi flexion tasks (Karim et al, 2014).…”