Brain Regions Associated with Phonological Processing in Dyslexia
The left superior temporal gyrus is specifically associated with phonological processing in individuals with dyslexia, serving as a key area that has been consistently related to core deficits in dyslexia across neuroimaging studies. 1
Neuroanatomical Basis of Phonological Processing in Dyslexia
Dyslexia involves distinct patterns of brain activation that differ from typical readers, particularly in regions critical for language processing:
Left Superior Temporal Gyrus (STG): This region shows reduced activation during phonological tasks in individuals with dyslexia and is the primary area associated with phonological processing deficits 1
Left Temporoparietal Region: Individuals with dyslexia demonstrate failure to properly activate this region during phonological tasks, which is crucial for normal reading development 2
Left Dorsolateral Prefrontal Cortex (DLPFC): Typically developing children recruit this area when making explicit phonological judgments, while children with dyslexia show reduced activation in this region 3
Left Inferior Temporo-Occipital Region: This area shows abnormal activation patterns in dyslexic individuals during visual word processing, with controls showing sharp activation around 180ms after word presentation while dyslexics fail to activate this area or show delayed responses 4
Functional Connectivity Patterns
The integrity of neural networks is crucial for phonological processing:
Hyperconnectivity between the left and right superior temporal gyri correlates with poorer language function, highlighting the importance of balanced interhemispheric communication 5
Disruption of interactions between brain networks (DMN, frontotemporo-parietal, and cingulo-opercular networks) affects language production and phonological processing 5
Clinical Implications
Understanding the neuroanatomical basis of phonological processing deficits in dyslexia has important clinical implications:
Phonological deficits impact both sublexical and lexical stages of spoken word processing 1
These deficits cannot be fully compensated through neural reorganization of lexical-distributional information at the single word level 1
Abnormal activation in right temporoparietal areas between 300-700ms post-stimulus onset during phonological tasks correlates with reduced performance on phonological processing measures 6
Structural Connections
The integrity of white matter tracts is crucial for phonological processing:
The arcuate fasciculus plays a critical role in language function, with damage to this structure impairing repetition and contributing to naming deficits 5
Damage to white matter tracts, including the frontal aslant tract and frontal inferior longitudinal fasciculus, is associated with persistent speech production impairments 5
In summary, while dyslexia involves multiple brain regions, the left superior temporal gyrus stands out as the key area specifically associated with phonological processing deficits, with the most recent and comprehensive evidence supporting this conclusion 1.