We are scanning with a 3T Philips Achieve X-Series scanner at NeuRA Imaging Centre.
We have several current projects ranging from Visual Perception, Decision Making to Working Memory.
High resolution fMRI
We employ cutting edge high resolution protocols resolving 1.2x1.2x1.2 mm. This resolution is critically
important since 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. This sheet of gray matter is deeply folded. Cortical locations that are far apart in the
2-dimensional sheet ofgray 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. To address this
shortcoming, we have developed and employed high resolution protocols covering occipital cortex for
functional imaging. Retinotopic mapping allows to test and validate the benefits of these high resolution
protocols, demonstrating high resolution is not only feasible but highly recommendable for everyday
imaging using clinical 3T scanners.
The image shows the result of a retinotopic mapping
experiment at two different resolutions. Only significantly active voxels are
coloured. Colours indicate different positions in the receptive field (not significance). This image shows that using high resolution protocols
results in very localised fMRI activity.
We routinely use retinotopic mapping techniques for
method research or as a tool for investigating the visual system.
As noise levels within fMRI acquisition decrease we are able to adequately image the spatiotemporal BOLD response. Our work seeks to truly understand the spatiotemporal hemodynamic response from both a theoretical and experimental perspective. By understanding this response we are developing methods to utilize these spatiotemporal properties to improve inferences of neural activity (click the image on the right to see a movie of spatiotemporal hemodynamics).