Neural Correlates of Visuomotor Learning

We are running our visuomotor study during a Magnetoencephalography (MEG) scan. MEG is a non-invasive, quiet, functional neuroimaging technique that measures magnetic fields created in the brain. Combined with a structural MRI scan, MEG allows us to visualise brain activations at greater spatial and temporal resolution compared to EEG or fMRI respectively.

Functional Connectivity in Developmental Disorders 

Im HY, Kheradmandsaadi Z, Asare A, Giaschi D (2023) Mapping whole-brain functional connectomes in amblyopia and dyslexia using resting-state fMRI. 29th Annual Meeting of the Organization for Human Brain Mapping, Montreal, Canada.

Good vision is essential for a child's overall development, including social and educational success. Here we investigated the whole-brain functional connectivity patterns of two common developmental disorders –amblyopia and dyslexia– that often disrupt various aspects of vision and have limited (often unsuccessful) treatment options. Amblyopia is reduced vision in one eye caused by abnormal visual experience early in life, and dyslexia is defined by poor word-reading ability despite average intelligence and motivation, but with an unknown cause. Although the two disorders are clinically quite different, they both involve similar disruptions in visual motion perception, face perception, reading, and attention. The neural correlates of these visual impairments have not been fully delineated for either amblyopia or dyslexia. Our cross-disorder approach has the potential to offer insight into unique and overlapping neural circuitry in amblyopia and dyslexia, informing transdiagnostic approaches to assessment and treatment.

Neural Correlates of Motion 

Task-based fMRI used to assess the effect of speed on motion perception. Read more here.

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. 

https://doi.org/10.1002/dys.1668  

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. 

https://doi.org/10.1016/j.neuropsychologia.2018.07.018 

Meier K, Partanen M, Giaschi D. (2018) Neural correlates of speed-tuned motion perception in healthy adults. Perception, 47, 660-683. 

https://doi.org/10.1177/0301006618771463 

Partanen M, Fitzpatrick K, Madler B, Edgell D, Bjornson B, Giaschi D. (2012) Cortical basis for dichotic pitch perception in developmental dyslexia. Brain and Language, 123,104-112.

https://doi.org/10.1016/j.bandl.2012.09.002 

Secen, J, Cullham, J, Ho C. & Giaschi, D. (2011). Neural correlates of the multiple-object tracking deficit in amblyopia.Vision Research, 51, 2517-2527.

https://www.sciencedirect.com/science/article/pii/S0042698911003683?via%3Dihub

Ho C, Giaschi D (2009) Low- and high-level motion perception deficits in anisometropic and strabismic amblyopia: evidence from fMRI. Vision Research, 49, 2891-901

https://www.sciencedirect.com/science/article/pii/S0042698909003447?via%3Dihub

Ho C, Giaschi D (2009) Low- and high-level first-order random-dot kinematograms: evidence from fMRI. Vision Research, 49, 1814-24

https://www.sciencedirect.com/science/article/pii/S0042698909001965

Giaschi D, Zwicker A, Young SA, Bjornson B. (2007) The role of cortical area V5/MT+ in speed-tuned directional anisotropies in global motion perception. Vision Research, 47(7), 887-898.

https://www.sciencedirect.com/science/article/pii/S004269890600589X?via%3Dihub

Giaschi D, Edwards V, Au Young S, Bjornson B (2005) Asymmetrical cortical activation by global motion in children with dyslexia. Journal of Vision, 5(8):848a.

Several groups have reported elevated motion coherence thresholds on global motion tasks in children and adults with dyslexia (eg. Edwards et al., 2004; Raymond & Sorensen, 1998; Talcott et al., 1998). The nature of the relationship between motion perception and reading deficits, however, has not been established. We used functional MRI to study the neural basis of the global motion deficit in 12 right-handed children with dyslexia and 12 age-matched controls. Area V5/MT+ was identified with a localizer task in which blocks of dots in expanding/contracting radial motion alternated with blocks of stationary dots. Activation in the V5/MT+ region was observed in 23 of 24 hemispheres in the control group and in all 24 hemispheres in the dyslexic group. This result is contrary to previous reports of reduced or no activation in response to moving stimuli in V5/MT+ in adults with dyslexia (Demb et al., 1998; Eden et al., 1996). Global motion direction discrimination was assessed using blocks of discrete trials of horizontally moving dots alternating with blocks of stationary dots. The coherence level was 85% or 30% on alternate motion blocks. Both groups showed more widespread activation when the coherence level was 30% than when the coherence level was 85%. At 30% coherence, activation was bilateral and symmetric in the controls. In contrast, the dyslexic group showed asymmetric activation with significantly reduced left hemisphere activation in V5/MT+, posterior occipital (putative V3A, V1, V2) and posterior parietal cortex. This finding, on motion tasks, is notable because, on reading tasks: 1) normal young readers show increasing left hemispheric lateralization as their reading fluency increases (Turkeltaub et al., 2003), and 2) children with dyslexia show reduced activation in left posterior regions compared to control children (Shaywitz et al., 2002). These results implicate left posterior cortex in both reading and global motion deficits in children with dyslexia.

Giaschi D, Jan J, Bjornson B, Au Young S, Tata M, Good W, Lyons C, Wong P (2003) Conscious visual abilities in a patient with early bilateral occipital damage. Developmental Medicine & Child Neurology, 45, 772-781.

https://onlinelibrary.wiley.com/doi/epdf/10.1111/j.1469-8749.2003.tb00888.x

Chen C-C, Giaschi D, Bjornson B, Au Young S (2003) Bold activation for detection and identification of motion-defined form in human brain. Society for Neuroscience Abstracts, 29, 591.18.

Figure-ground segregation can be achieved in a random dot kinematogram when the dots of the figure and the ground move in different directions. Focal cortical lesions in the region of the temporoparietal occipital junction disrupt the perception of such motion-defined (MD) forms, but some patients show dissociation between the detection and identification of MD form. We used functional MRI to investigate the neural basis of this dissociation by examining brain activation during passive viewing and during active identification of MD form.