Table 3.
Systematic review of the Neuroanatomical correlates of dyslexia and the neuroanatomic correlates of dyscalculia.
| Method | Neuroanatomical correlates of dyslexia | Neuroanatomical correlates of dyscalculia |
|---|---|---|
| Functional Neuroimaging Studies (fMRI, PET) |
Hypoactivation during phonological tasks: •Left superior frontal gyrus (105) •Left middle frontal gyrus (105) •Left inferior frontal gyrus (106–108) •Left superior temporal gyrus (107, 109–111) •Left superior temporal sulcus (107, 109–112) •Left middle temporal gyrus (113) •Left inferior temporal gyrus (108, 109, 114) •Left fusiform gyrus (112, 114–116) •Left superior parietal cortex (117) •Left inferior parietal cortex (117) •Left angular gyrus (105, 109, 110, 118, 119) •Left supramarginal gyrus (120, 121) •Left middle occipital gyrus (112) Hyperactivation during phonological tasks: •Right medial prefrontal cortex (113) •Left primary motor cortex (109, 113) •Left anterior insula (109, 110, 113) •Left caudate nuclei (109, 110) •Lobule VI of the Left cerebellum (122) •Precuneus (112) No significant differences in activation between individuals with dyslexia and controls •Cerebellum (123) Null Findings: No significant differences in activation between individuals with dyslexia and controls during phonological tasks (129) |
Hypoactivation during numerical magnitude tasks: •Left superior frontal gyrus (124) •Left medial prefrontal cortex (125) •Right fusiform gyrus (124, 125) •Right intraparietal sulcus (125) •Bilateral intraparietal sulci (124, 126, 127) Hyperactivation during numerical magnitude tasks: •Right superior frontal gyrus (124) •Left postcentral gyrus (124) •Left angular gyrus (124, 126, 128) •Bilateral supramarginal gyrus (124) Null findings: No significant differences in activation between individuals with dyscalculia and controls during numerical magnitude tasks (129) |
| Structural Neuroimaging Studies (MRI) |
Lower gray matter volume vs. controls: •Right middle frontal gyrus (130) •Left inferior frontal gyrus (115, 131) •Left inferior temporal gyrus (115) •Left fusiform gyrus (115, 132) •Left angular gyrus (115, 132) •Occipitotemporal cortex (133) Greater cortical thickness vs. controls: •Right superior temporal gyrus (134) •Left fusiform gyrus (134) No difference in gray matter volume between individuals with dyslexia and controls in the following regions •Cerebellum (135) |
Lower gray matter volume vs. controls: •Left fusiform gyrus (132) •Left angular gyrus (132) •Right intraparietal sulcus (136) Null findings: No difference in matter volume between individuals with dyslexia and controls (135) |
| Functional Connectivity Studies (DTI) |
Lower functional connectivity in the following white matter tracts vs. controls: •Right superior longitudinal fasciculus (137) •Left arcuate fasciculus, connecting the left inferior frontal gyrus and the left auditory cortex (138) •Reduced connectivity between the left inferior frontal gyrus and multiple left posterior temporal areas, including the left fusiform gyrus, left inferior temporal gyrus, left middle temporal gyrus, and left superior temporal gyrus (139) •White matter tracts between the right parahippocampal gurus the left fusiform gyrus (140) •White matter tracts between the left angular gyrus and left lingual gyrus, as well as the left angular gyrus and the left cerebellum (105) •Left auditory thalamus and the left planum temporale (141) •Left angular gyrus and left superior temporal gyrus (123) Greater functional connectivity between the following structures among individuals with dyslexia vs. controls: •Left cerebellum and the left supramarginal gyrus (122) •Thalamus and the inferior parietal cortex (117) |
Lower functional connectivity in the following white matter tracts vs. controls: •Inferior fronto-occipital fasciculus and inferior longitudinal fasciculus, connecting the right fusiform gyrus and right intraparietal sulcus (145) •Bilateral posterior superior longitudinal fasciculus (146) Greater functional connectivity between the following structures among individuals with dyscalculia vs. controls: •Bilateral intraparietal sulci and the left superior frontal gyrus (147) •Bilateral intraparietal sulci, the right superior temporal gyrus, and the right supramarginal gyrus (148) •Primary visual cortex and inferior occipital cortex (129) •Primary visual cortex and fusiform gyrus (129) Null findings: No significant differences between individuals with dyslexia and typical readers in the following white matter tracts: •Bilateral arcuate fasciculus (142) •Corona radiata (142) |
|
Null findings: No significant differences between individuals with dyslexia and controls in the following white matter tracts: •Bilateral arcuate fasciculus (142) •Corona radiata (142–144) |
||
| Lesion-Symptom Mapping Studies |
Alexia associated with damage to: •Left inferior frontal gyrus (115, 149, 150) •Right Posterior middle temporal gyrus (151) •Right fusiform gyrus (152) •Left fusiform gyrus (149, 153–155) •Left angular gyrus, via the posterior cerebral artery (156, 157) •Left supramarginal gyrus (158) |
Acquired dyscalculia associated with damage to: •Left thalamus (159, 160) •Left angular gyrus (161, 162) •Left intraparietal sulcus (163) |
The bolded and italicized brain regions were identified as a neuroanatomical correlate of dyslexia or dyscalculia in all four types of studies in included in the systematic review (functional neuroimaging studies, structural neuroimaging studies, functional connectivity studies, and lesion-symptom mapping studies).