|Hee Yeon Im|
|UBC Vision Lab|
|Visual Cognition Group|
Neural Correlates of Reading Disability
To determine, using functional magnetic resonance imaging (fMRI), if overlapping cortical networks for reading and temporal processing are compromised in individuals with dyslexia. This research is funded by the Canadian Institutes of Health Research (CIHR).
Reading and Cognitive Abilities
As a follow up to the fMRI study, using the Cambridge Brain Science Platform, we are looking to assess the relationship between reading and cognitive ability in both heatlhy controls and participants with dyslexia.
Select Completed Projects
Kheradmandsaadi, Z., Im, H.Y., Partanen, M., Siegel, L.S., & Giaschi, D. (2023). Effects of reading intervention on whole-brain resting-state functional connectivity in dyslexia. Organization for Human Brain Mapping, Montreal, Canada
Here, we used a whole-brain, functional connectome approach to fully examine the effects of an intensive 3-month school-based reading intervention program on resting-state FC in children with dyslexia. These children comprise a subset of those for which recently reported on the effectiveness of this intervention in improving various aspects of reading (Partanen et al.,2019). We also examined correlations between resting-state FC changes and reading ability changes following the intervention. The results from the dyslexia group were compared with those from typical readers who provided measures of maturational changes.
Kheradmandsaadi, Z., Im, H.Y., Partanen, M., Siegel, L.S., & Giaschi, D. (2023). Dorsal and lateral visual processing stream functional connectivity in children with dyslexia and typical readers. Language Sciences Research Day, Vancouver, Canada
Dyslexia is a neurodevelopmental reading disorder associated with deficits in motion perception. These deficits have been attributed to vulnerability in the dorsal visual processing stream involved in motion, attention, and visually-guided action. Contrary to this traditional view, an alternative framework proposes a lateral stream, that includes visual areas MT and lateral occipital complex (LOC). This lateral stream is proposed to mediate both motion perception and language processing, and its function may be disrupted by dyslexia. To investigate whether the brain’s functional connection is altered in either or both visual streams in dyslexia, we examined functional connectivity between regions of interest (ROIs) in the dorsal and lateral streams.
Partanen M, DHC Kim, Rauscher A, Siegel LS, Giaschi DE (2021). White matter but not grey matter predicts change in reading skills after intervention. Dyslexia, 27(2), 224-244.
Partanen M, Siegel L, Giaschi D. (2019) Effect of reading intervention and task difficulty on orthographic and phonological reading systems in the brain. Neuropsychologia, 130, 13-25.
Partanen M; Fitzpatrick K; Mädler B; Edgell D; Bjornson B; Giaschi DE (2012) Cortical basis for dichotic pitch perception in developmental dyslexia. Brain and Language , 123 (2), 104-112
The current study examined auditory processing deficits in dyslexia using a dichotic pitch stimulus and functional MRI. Cortical activation by the dichotic pitch task occurred in bilateral Heschl's gyri, right planum temporale, and right superior temporal sulcus. Adolescents with dyslexia, relative to age-matched controls, illustrated greater activity in left Heschl's gyrus for random noise, less activity in right Heschl's gyrus for all auditory conditions, and less activity in right superior temporal sulcus for a dichotic melody. Subsequent analyses showed that these group differences were attributable to dyslexic readers who performed poorly on the psychophysical task. Furthermore, behavioral performance on phonological reading was correlated to activity from dichotic conditions in right Heschl's gyrus and right superior temporal sulcus. It is postulated that these differences between reader groups is primarily due to a noise exclusion deficit shown previously in dyslexia.
Boden C, Giaschi D (2007) M-stream deficits and reading-related visual processes in developmental dyslexia. Psychological Bulletin, 133, 346-66
Some visual processing deficits in developmental dyslexia have been attributed to abnormalities in the subcortical M stream and/or the cortical dorsal stream of the visual pathways. The nature of the relationship between these visual deficits and reading is unknown. The purpose of the present article was to characterize reading-related perceptual processes that may link the visual deficits to reading problems. We identified contrast sensitivity, position encoding, oculomotor control, visual attention, parafoveal/foveal interactions, and saccadic suppression as potential reading-related dorsal stream processes. We then evaluated the role of each process in reading and the status of each process in dyslexia. In theory, a number of dorsal stream processes (e.g., oculomotor control and visual attention) might contribute to reading problems in developmental dyslexia. More work is needed to demonstrate the connection empirically.
Visser T, Boden C, Giaschi D (2004) Children with dyslexia: evidence for visual attention deficits in perception of rapid sequences of objects. Vision Research, 44, 2521-2535.
Edwards V, Giaschi D, Dougherty R, Edgell D, Bjornson B, Lyons C, Douglas R (2004) Psychophysical indices of temporal processing abnormalities in children with dyslexia. Developmental Neuropsychology, 25, 321-354.
Children with dyslexia and children progressing normally in reading performed several perceptual tasks to determine (a) the psychophysical measures that best differentiate children with dyslexia from children with average reading abilities; (b) the extent of temporal processing deficits in a single, well-defined group of children with dyslexia; and (c) the co-occurrence of visual and auditory temporal processing deficits in children with dyslexia. Four of our twelve psychophysical tasks indicated differences in temporal processing ability between children with dyslexia and children with good reading skills. These included two auditory tasks (dichotic pitch perception and FM tone discrimination) and two visual tasks (global motion perception and contrast sensitivity). The battery of 12 tasks successfully classified 80% of the children into their respective reading-level groups. Within the group of children with dyslexia who had temporal processing deficits, most were affected in either audition or vision; few children were affected in both modalities. The observed deficits suggest that impaired temporal processing in dyslexia is most evident on tasks that require the ability to synthesize local, temporally modulated inputs into a global percept and the ability to extract the resultant global percept from a noisy environment.