Are fMRI Responses Localized to Sub-millimeter Functional Structures?
Recently introduced fMRI techniques provide the capability of visualizing elevat ed neuronal activity with spatiotemporal specificity and resolution that has not be en previously available with other non-invasive methods. Such a capability is essential for a system level understanding of human brain function, which posses ses unique attributes that are distinct from animal models and cannot be investigate d with invasive techniques available for animal studies. Despite the indispensable role of the BOLD fMRI technique in mapping human brain function, ability of mapp ing sub-millimeter functional structures such as cortical columns is controversial. We have investigated spatial specificity and resolution of fMRI using well-established anesthetized animal models, rat forepaw stimulation and cat orientation column. We found that columnar structures can be mapped by using metabolism-based early negative BOLD signal or draining vessels-free perfusion-based fMRI. Jack Lancaster (University o
