The spatial extent of the BOLD response.

An fMRI study of human visual cortex in response to spatiotemporal properties of visual stimuli

  ABSTRACT  Background: The brain response to temporal frequencies (TF) has been already reported, but with no study reported for different TF with respect to various spatial frequencies (SF).  Materials and Methods: fMRI was performed by 1.5T GE-system in 14 volunteers during checkerboard, with TFs of 4, 6, 8 and 10Hz in low and high SFs of 0.5 and 8cpd.  Results: Average percentage BOLD signa...

Repeatability of Detecting Visual Cortex Activity in Functional Magnetic Resonance Imaging

Introduction As functional magnetic resonance imaging (fMRI) is too expensive and time consuming, its frequent implementation is difficult. The aim of this study is to evaluate repeatability of detecting visual cortex activity in fMRI. Materials and Methods In this study, 15 normal volunteers (10 female, 5 male; Mean age±SD: 24.7±3.8 years) attended. Functional magnetic resonance images were ob...

Caffeine reduces the activation extent and contrast-to-noise ratio of the functional cerebral blood flow response but not the BOLD response

Measures of the spatial extent of functional activation are important for a number of functional magnetic resonance imaging (fMRI) applications, such as pre-surgical planning and longitudinal tracking of changes in brain activation with disease progression and drug treatment. The interpretation of the data from these applications can be complicated by inter-subject or inter-session variability ...

Re-imagining Research: A Bold Call, but Bold Enough?; Comment on “Experience of Health Leadership in Partnering with University-Based Researchers in Canada: A Call to ‘Re-Imagine’ Research”

Many articles over the last two decades have enumerated barriers to and facilitators for evidence use in health systems. Bowen et al’s article “Response to Experience of Health Leadership in Partnering with University-Based Researchers: A Call to ‘Re-imagine Research’” furthers the debate by focusing on an under-explored research area (health system design and health service organization) with ...

Influence of BOLD Contributions to Diffusion fMRI Activation of the Visual Cortex

Reliance on the hemodynamic response as a surrogate marker of neural activity imposes an intrinsic limit on the spatial specificity of functional MRI. An alternative approach based on diffusion-weighted functional MRI (DfMRI) has been reported as a contrast less reliant on hemodynamic effects, however current evidence suggests that both hemodynamic and unique neural sources contribute to the di...

Tackling HIV in MENA: Talk Is Not Enough–It Is Time for Bold Actions: A Response to Recent Commentaries