Functional Dynamics of Dorsal and Ventral Reading Networks in Bilinguals

Abstract

word count: 200 words

Neural correlates of phonological, orthographic and semantic reading processing in dyslexia

“…On the other hand, the hippocampus has been largely ignored as a region of interest in reading-related tasks and in studies examining differences among readers with dyslexia and controls (but see Krishnan et al, 2016 ). However, results from single-word reading and sentence processing MRI studies conducted in our lab ( Molinaro et al, 2015 ; Oliver et al, 2017 ; Rueckl et al, 2015 ) and recent findings confirm the relevance of the hippocampus in semantic processes during reading ( Binder et al, 2009 ; Duff and Brown-Schmidt, 2012 ; Piai et al, 2016 ; see Jaimes-Bautista et al, 2015 for a neuropsychological review). Additionally, recent evidence has suggested that hippocampal function may be associated with sequential procedural learning deficits observed in readers with dyslexia ( Krishnan et al, 2016 ).…”

“…Importantly, we will also examine between-group differences in task-related functional connectivity for each of the four experimental conditions (i.e., Consistent Words, Inconsistent Words, Pseudowords, Pseudohomophones) among the left hemisphere regions showing hypoactivation for readers with dyslexia versus control readers. Since functional connectivity is thought to reflect the prior history of coactivations, in line with a Hebbian-like learning rule ( Harmelech et al, 2013 ; Hebb, 1949 ; Oliver et al, 2017 ), the present study constitutes an important attempt to further examine if the areas showing regional hypoactivations in dyslexia also show differences in functional connectivity for readers with and without dyslexia in terms of phonological, orthographic and semantic-related processes. If hypoactivation in readers with dyslexia reflects deficits in adequately resolving reading processes at the regional level, it could be possible to predict increases in functional connectivity among these regions in individuals with dyslexia to compensate for regional reading deficits.…”

“…Proficient reading involves mapping visual features, such as letters (orthography) to sound (input phonology) and to meaning (semantics) as well as, for reading aloud, to articulatory codes (output phonology) that generate the corresponding speech sounds (phonetics). These reading operations are typically accomplished by means of two processing streams that run through left hemisphere regions: a lexical ventral stream , including the ventral occipitotemporal (vOT) and anterior inferior frontal gyrus (IFG) regions, that supports mapping of orthographic-lexical stimuli to whole words (i.e., the direct route); and a non-lexical dorsal stream , encompassing the parietal lobe, superior temporal gyrus (STG) and posterior IFG, that is thought to subserve orthographic-to-phonological conversion (i.e., the indirect route; Oliver et al, 2017 ; Pugh et al, 2001 ; Sandak et al, 2004 ; Schlaggar and McCandliss, 2007 ). Neuroimaging research using reading tasks has consistently shown regional hypoactivation for readers with dyslexia as opposed to control readers in all of these left hemisphere ventral and dorsal areas, including IFG, temporal and parietal regions, and vOT (see Maisog et al, 2008 , Paulesu et al, 2014 ; Richlan et al, 2009 , Richlan et al, 2011 , for metanalytical reviews).…”

Reading-related functional activity in children with isolated spelling deficits and dyslexia

“…The ability to process written language involves the interplay of multiple brain regions for visual, language and motor processing (Dehaene et al, 2015). Two main streams within the left hemisphere have been described for reading-related neural processing (Oliver et al, 2017;Paz-Alonso et al, 2018;Price, 2012;Pugh et al, 2001;Schlaggar & McCandliss, 2007). The sublexical dorsal stream bonds left parietal and superior temporal regions with the posterior inferior frontal gyrus (IFG) "pars opercularis" (BA 44), enabling phonological decoding procedures based on grapheme-phoneme conversion rules.…”

Structural Brain Network Correlated with Reading Impairment in Alzheimer’s Disease

“…In the Japanese language system, reading involves both phonograms (Kana) and ideograms (Kanji), and thus strongly entails the conversion of orthography to meaning [5]. Reading operations in the alphabetic writing system are typically accomplished by means of two processing streams: the parietal lobe, superior temporal gyrus, and posterior inferior frontal gyrus, which are thought to subserve orthographic-to-phonological conversion; and the ventral occipitotemporal and anterior inferior frontal gyrus regions, which support orthographic-to-lexical conversation [6][7][8][9][10]. However, there has been no study evaluating the changes to brain neuralconnectivity responsible for language dysfunction in Japanese AD patients.…”