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Mark Schira

mobile:+ 61 (0) 4 0595 4853

I am interested in the visual system in general and retinotopic organization and the perception of contours and objects in particular. I use psychophysical methods and EEG, but primarily I work with fMRI, in particular high resolution fMRI.

High resolution fMRI

Partial voluming is a major confounder commonly ignored in fMRI. The blood oxygen level dependent changes measured by fMRI, typically occur in the thin (roughly 2.5 mm thick) sheet of gray matter that forms the cortex. This sheet of gray matter is deeply folded. Cortical locations that are far apart in the 2-dimensional sheet of gray matter are often extremely close in 3-dimensional space. Large fMRI voxels (3 mm +) will sample and confuse signals from two rather distant parts of the cortical surface (partial voluming), when they are adjacent to each other due to cortical folding.

 A high resolution EPI 0.9x0.9x1 mm. Marked in green is white matter, marked in blue and red are blood vessels.