Neural patterns of word processing differ in children with dyslexia and isolated spelling deficit

Abnormal brain activation during speech perception and production in children and adults with reading difficulty

Reading difficulty (RD) is associated with phonological deficits; however, it remains unknown whether the phonological deficits are different in children and adults with RD as reflected in foreign speech perception and production. In the current study, using functional Near-infrared spectroscopy (fNIRS), we found less difference between Chinese adults and Chinese children in the RD groups than the control groups in the activation of the right inferior frontal gyrus (IFG) and the dorsolateral prefrontal cortex (DLPFC) during Spanish speech perception, suggesting slowed development in these regions associated with RD. Furthermore, using multivariate pattern analysis (MVPA), we found that activation patterns in the left middle temporal gyrus (MTG), premotor, supplementary motor area (SMA), and IFG could serve as reliable markers of RD. We provide both behavioral and neurological evidence for impaired speech perception and production in RD readers which can serve as markers of RD.

Letter-speech sound integration in typical reading development during the first years of formal education

This study investigated the neural basis of letter and speech sound (LS) integration in 53 typical readers (35 girls, all White) during the first 2 years of reading education (ages 7-9). Changes in both sensory (multisensory vs unisensory) and linguistic (congruent vs incongruent) aspects of LS integration were examined. The left superior temporal cortex and bilateral inferior frontal cortex showed increasing activation for multisensory over unisensory LS over time, driven by reduced activation to speech sounds. No changes were noted in the congruency effect. However, at age nine, heightened activation to incongruent over congruent LS pairs were observed, correlating with individual differences in reading development. This suggests that the incongruency effect evolves at varying rates depending on reading skills.

Atypical characteristic changes of surface morphology and structural covariance network in developmental dyslexia

BACKGROUND

Developmental dyslexia (DD) is a neurodevelopmental disorder that is characterized by difficulties with all aspects of information acquisition in the written word, including slow and inaccurate word recognition. The neural basis behind DD has not been fully elucidated.

METHOD

The study included 22 typically developing (TD) children, 16 children with isolated spelling disorder (SpD), and 20 children with DD. The cortical thickness, folding index, and mean curvature of Broca's area, including the triangular part of the left inferior frontal gyrus (IFGtriang) and the opercular part of the left inferior frontal gyrus, were assessed to explore the differences of surface morphology among the TD, SpD, and DD groups. Furthermore, the structural covariance network (SCN) of the triangular part of the left inferior frontal gyrus was analyzed to explore the changes of structural connectivity in the SpD and DD groups.

RESULTS

The DD group showed higher curvature and cortical folding of the left IFGtriang than the TD group and SpD group. In addition, compared with the TD group and the SpD group, the structural connectivity between the left IFGtriang and the left middle-frontal gyrus and the right mid-orbital frontal gyrus was increased in the DD group, and the structural connectivity between the left IFGtriang and the right precuneus and anterior cingulate was decreased in the DD group.

CONCLUSION

DD had atypical structural connectivity in brain regions related to visual attention, memory and which might impact the information input and integration needed for reading and spelling.

Words as Visual Objects: Neural and Behavioral Evidence for High-Level Visual Impairments in Dyslexia

Developmental dyslexia is defined by reading impairments that are disproportionate to intelligence, motivation, and the educational opportunities considered necessary for reading. Its cause has traditionally been considered to be a phonological deficit, where people have difficulties with differentiating the sounds of spoken language. However, reading is a multidimensional skill and relies on various cognitive abilities. These may include high-level vision—the processes that support visual recognition despite innumerable image variations, such as in viewpoint, position, or size. According to our high-level visual dysfunction hypothesis, reading problems of some people with dyslexia can be a salient manifestation of a more general deficit of high-level vision. This paper provides a perspective on how such non-phonological impairments could, in some cases, cause dyslexia. To argue in favor of this hypothesis, we will discuss work on functional neuroimaging, structural imaging, electrophysiology, and behavior that provides evidence for a link between high-level visual impairment and dyslexia.