A Mini-Review: Toward a Comprehensive Theory of Dyslexia

Abstract

Current research suggests that the neurobiological substrate of dyslexia involves the dysfunctional orchestration of a multi-dimensional and hierarchical circuitry of at least three neuronal networks. This circuitry principally involves the posterior corpus callosum, left arcuate fasciculous, and the right frontostriatal attentional control network. The key to understanding the disability and in forging a comprehensive theory of dyslexia may be found in investigations aimed at interactions among all three networking territories.Keywords: Dyslexia; Corpus callosum; Arcuate fasciculus; Frontostriatal attention control Developmental dyslexia is a hereditary, neurocognitive-based learning difficulty, usually identified early in children's primary education when young children struggle to acquire proficiency in beginning reading skills. Prevalence estimates vary, ranging from 5% to as high as 20% [1]. After more than a century of research and the implementation of a broad range of remedial strategies, this disability, which affects individuals irrespective of their level of intelligence, motivation to learn and adequate educational and social circumstances, remains relatively intransigent to educational approaches. The reading, spelling, and array of related cognitive difficulties found in children with dyslexia persist into adulthood [2]. Familial studies indicate an etiological origin in an intricate interplay of neurobiological, genetic, epigenetic, and environmental factors [3].

Verbal fluency in relation to reading ability in students with and without dyslexia

“…Another possible explanation is related to the fact that verbal fluency has been reported to occur lateralized to the left hemisphere (Gaillard et al, 2003) with an increasing lateralization with age (Holland et al, 2001). This coincides with the atypical lateralization hypothesis in dyslexia, where studies have found that typically lateralized abilities are less lateralized (Habib, 2000; Vanderauwera et al, 2016; for a general discussion, see Kershner, 2015). This atypical pattern, specifically less left-lateralized activation, has been found in individuals with dyslexia during performance of a silent letter fluency task (Illingworth & Bishop, 2009).…”

“…Brain imaging studies of individuals with dyslexia have found alterations in both cortical and subcortical structures and activation patterns in individuals with dyslexia. These findings include atypical cortical lateralization (Habib, 2000; see Kershner, 2015; Vanderauwera et al, 2016), suggested to derive from abnormalities in early stages of brain maturation and development (Galaburda, 2006), and decreases in gray matter in the left temporal lobe, frontal lobe, striatum, thalamus, and cerebellum (Brown et al, 2001; Eckert, 2004; for a mini-review, see Kershner, 2015).…”

Designing a Computerized Neuro-Cognitive Program for Early Diagnosing Children at Risk for Dyslexia

“…To achieve the objective, the visual and auditory working memories were measured. According to various scientific studies and research, these two important cognitive components are among the most important affected cognitive components in dyslexia [14,20]. Furthermore, the information processing theory is considered as one of the most authentic theories in this field [29].…”

“…Therefore, in this research, we have designed a computer based screening program that can be used as a prediction method in schools in the absence of trained professionals. We have focused on neuro-cognitive impairments of dyslexic individuals, instead of reading ability, since it is believed that dyslexia is the result of some neural circuits dysfunctions and alterations [14], such as Fronto-striatal circuits [15], left arcuate fasciculus [16], and corpus callosum [14]. Visual and auditory working memories are among the most highlighted affected cognitive skills due to these alterations [17].…”