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Reading the dyslexic brain: multiple dysfunctional routes revealed by a new meta-analysis of PET and fMRI activation studies.

Paulesu E, Danelli L, Berlingeri M - Front Hum Neurosci (2014)

Bottom Line: Following binomial tests on the clusters, we found left hemispheric network specific for normal controls (i.e., of reduced involvement in dyslexics) including the left inferior frontal, premotor, supramarginal cortices and the left infero-temporal and fusiform regions: these were preferentially associated with reading and the visual-to-phonology processes.No cluster was identified in area V5 for no task, nor cerebellar clusters showed a reduced association with dyslexics.Additional deficits of motor and attentional systems relevant for reading may be associated with altered functionality of dorsal left fronto-parietal cortex.

View Article: PubMed Central - PubMed

Affiliation: Department of Psychology, University of Milano-Bicocca Milan, Italy ; NEUROMI- Milan Center for Neuroscience, University of Milano-Bicocca Milan, Italy ; fMRI - Unit, Istituto di Ricovero e Cura a Carattere Scientifico Galeazzi Milan, Italy.

ABSTRACT
Developmental dyslexia has been the focus of much functional anatomical research. The main trust of this work is that typical developmental dyslexics have a dysfunction of the phonological and orthography to phonology conversion systems, in which the left occipito-temporal cortex has a crucial role. It remains to be seen whether there is a systematic co-occurrence of dysfunctional patterns of different functional systems perhaps converging on the same brain regions associated with the reading deficit. Such evidence would be relevant for theories like, for example, the magnocellular/attentional or the motor/cerebellar ones, which postulate a more basic and anatomically distributed disorder in dyslexia. We addressed this issue with a meta-analysis of all the imaging literature published until September 2013 using a combination of hierarchical clustering and activation likelihood estimation methods. The clustering analysis on 2360 peaks identified 193 clusters, 92 of which proved spatially significant. Following binomial tests on the clusters, we found left hemispheric network specific for normal controls (i.e., of reduced involvement in dyslexics) including the left inferior frontal, premotor, supramarginal cortices and the left infero-temporal and fusiform regions: these were preferentially associated with reading and the visual-to-phonology processes. There was also a more dorsal left fronto-parietal network: these clusters included peaks from tasks involving phonological manipulation, but also motoric or visuo-spatial perception/attention. No cluster was identified in area V5 for no task, nor cerebellar clusters showed a reduced association with dyslexics. We conclude that the examined literature demonstrates a specific lack of activation of the left occipito-temporal cortex in dyslexia particularly for reading and reading-like behaviors and for visuo-phonological tasks. Additional deficits of motor and attentional systems relevant for reading may be associated with altered functionality of dorsal left fronto-parietal cortex.

No MeSH data available.


Related in: MedlinePlus

A schematic flowchart diagram showing the procedure by which data are selected, clusters are estimated, tested and classified using HC and ALE.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4227573&req=5

Figure 2: A schematic flowchart diagram showing the procedure by which data are selected, clusters are estimated, tested and classified using HC and ALE.

Mentions: However, hierarchical clustering does not provide a statistical test of the spatial significance of a given cluster against a random reference distribution of regional effects. This is permitted by the ALE approach (Turkeltaub et al., 2002; Eickhoff et al., 2009) that we used to complement our analyses. A schematic flowchart diagram is now reported in Figure 2. A previous example of this combined approach can be found in Crepaldi et al. (2013), where, in addition to the dual meta-analytical procedure, the clusters were assessed post-hoc not only for simple effects but also for interaction effects, as in the present study.


Reading the dyslexic brain: multiple dysfunctional routes revealed by a new meta-analysis of PET and fMRI activation studies.

Paulesu E, Danelli L, Berlingeri M - Front Hum Neurosci (2014)

A schematic flowchart diagram showing the procedure by which data are selected, clusters are estimated, tested and classified using HC and ALE.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4227573&req=5

Figure 2: A schematic flowchart diagram showing the procedure by which data are selected, clusters are estimated, tested and classified using HC and ALE.
Mentions: However, hierarchical clustering does not provide a statistical test of the spatial significance of a given cluster against a random reference distribution of regional effects. This is permitted by the ALE approach (Turkeltaub et al., 2002; Eickhoff et al., 2009) that we used to complement our analyses. A schematic flowchart diagram is now reported in Figure 2. A previous example of this combined approach can be found in Crepaldi et al. (2013), where, in addition to the dual meta-analytical procedure, the clusters were assessed post-hoc not only for simple effects but also for interaction effects, as in the present study.

Bottom Line: Following binomial tests on the clusters, we found left hemispheric network specific for normal controls (i.e., of reduced involvement in dyslexics) including the left inferior frontal, premotor, supramarginal cortices and the left infero-temporal and fusiform regions: these were preferentially associated with reading and the visual-to-phonology processes.No cluster was identified in area V5 for no task, nor cerebellar clusters showed a reduced association with dyslexics.Additional deficits of motor and attentional systems relevant for reading may be associated with altered functionality of dorsal left fronto-parietal cortex.

View Article: PubMed Central - PubMed

Affiliation: Department of Psychology, University of Milano-Bicocca Milan, Italy ; NEUROMI- Milan Center for Neuroscience, University of Milano-Bicocca Milan, Italy ; fMRI - Unit, Istituto di Ricovero e Cura a Carattere Scientifico Galeazzi Milan, Italy.

ABSTRACT
Developmental dyslexia has been the focus of much functional anatomical research. The main trust of this work is that typical developmental dyslexics have a dysfunction of the phonological and orthography to phonology conversion systems, in which the left occipito-temporal cortex has a crucial role. It remains to be seen whether there is a systematic co-occurrence of dysfunctional patterns of different functional systems perhaps converging on the same brain regions associated with the reading deficit. Such evidence would be relevant for theories like, for example, the magnocellular/attentional or the motor/cerebellar ones, which postulate a more basic and anatomically distributed disorder in dyslexia. We addressed this issue with a meta-analysis of all the imaging literature published until September 2013 using a combination of hierarchical clustering and activation likelihood estimation methods. The clustering analysis on 2360 peaks identified 193 clusters, 92 of which proved spatially significant. Following binomial tests on the clusters, we found left hemispheric network specific for normal controls (i.e., of reduced involvement in dyslexics) including the left inferior frontal, premotor, supramarginal cortices and the left infero-temporal and fusiform regions: these were preferentially associated with reading and the visual-to-phonology processes. There was also a more dorsal left fronto-parietal network: these clusters included peaks from tasks involving phonological manipulation, but also motoric or visuo-spatial perception/attention. No cluster was identified in area V5 for no task, nor cerebellar clusters showed a reduced association with dyslexics. We conclude that the examined literature demonstrates a specific lack of activation of the left occipito-temporal cortex in dyslexia particularly for reading and reading-like behaviors and for visuo-phonological tasks. Additional deficits of motor and attentional systems relevant for reading may be associated with altered functionality of dorsal left fronto-parietal cortex.

No MeSH data available.


Related in: MedlinePlus