Q2. How many voxels were needed to correct for multiple comparisons?
Assuming an individual voxel type The authorerror of P < 0.001, a cluster threshold of 21 contiguous resampled voxels (equivalent to eight original voxels) was indicated as necessary to correct for multiple voxel comparisons at P < 0.05.
Q3. How many orthogonal regressors were used to reduce variance?
A total of nine orthogonal regressors (covariates of no interest) were used to reduce variance unlikely to reflect functional connectivity-related neuronal activity (Fair et al., 2007; Fox et al., 2005; Villalobos et al., 2005): six regressors corresponding to the six parameters obtained by the rigid body head motion correction; three regressors corresponding to the whole brain, white matter and ventricular (CSF) signal, which included the averaged signals over voxels within the respective SPM template masks.
Q4. What were the children excluded from the study?
Children with a history of neurological diseases, psychiatric disorders,uncorrected-vision problems and children from families with a foreign language background were excluded from the study.
Q5. What is the popular method for the in vivo examination of the cooperation between brain regions?
A popular method for the in vivo examination of the cooperation between brain regions is called functional connectivity MRI (fcMRI), which examines the temporal coherence in which brain areas are engaged (Biswal et al., 1995; Cordes et al., 2000; Friston, 1994; Lowe et al., 1998).
Q6. What regions of the brain were found to have greater connectivity for dyslexics than controls?
Greater connectivity for dyslexics than controls for ROI4 was found mainly in the left superior temporal gyrus and the left insula.
Q7. How many regressors were included in the analysis?
four regressors related to the stimuli were included in order to minimize the stimulus-related variance (Brown et al., 2005; Fair et al., 2006; Miezin et al., 2000; Schlaggar et al., 2002).
Q8. What is the role of the VWF-System in dyslexia?
Adults with dyslexia show functional deficits in several brain regions including the so-called “Visual Word Form Area” (VWFA), which is implicated in visual word processing and located within the larger left occipitotemporal VWF-System.
Q9. What is the role of the left occipitotemporal system in dyslexia?
The current findings add to their understanding of dyslexia by showing that functional disconnection of the left occipitotemporal system is limited to the small VWFA region crucial for automatic visual word processing, and emerges early during reading acquisition in children with dyslexia, along with deficits in orthographic and phonological processing of visual word forms.
Q10. What was the first step of the seed-voxel correlation mapping analysis?
The initial step of the seed-voxel correlation mapping analysis (Biswal et al., 1995) was to define five non-overlapping seed regions of interest (ROIs; spheres with a 6mm radius) (Figure 1a), centered on the VWFA of the fusiform gyrus (Cohen et al., 2000) and covering neighbouring areas along a posterior-anterior axes in the left hemisphere.
Q11. What is the difference between functional connectivity and hypothesis-driven fcMRI?
Compared to effective connectivity (the influence one neural system exertsover another), functional connectivity (temporal correlations between remote, spontaneous neurophysiological events) has the advantage that it is a data-driven rather than a hypothesis-driven type of analysis, thus not reducing its validity to the validity of the model (Friston, 1994).