High-resolution fMRI and Neurovascular Coupling in the Visual Cortex”
To understand cortical function it is important to gain a better understanding of the functional units of the cortex, i.e., its columns and layers. High-resolution fMRI can potentially offer tremendous advantages for the study of cortical microcircuits in vivo, evidenced by the increasing interest in high-resolution fMRI. However, many questions remain about the size of the cortical features that can be resolved, and which neural processes exactly are reflected in the BOLD signal. In this talk, I will discuss our work on high-resolution fMRI and electrophysiology in the primary visual cortex (V1) and temporal lobe of awake and anesthetized macaques, and our most recent work on the mechanisms of the BOLD response. Here, we exploit the well-studied layered structure of V1 to investigate whether we can detect laminar differences in the BOLD, cerebral blood flow (CBF) and cerebral blood volume (CBV) responses for excitatory and inhibitory stimuli. Not only did we find that the mechanisms for the positive and negative BOLD responses differ, but we also found laminar differences in neurovascular coupling, suggesting that high-resolution fMRI can potentially be used to resolve the functional microcircuits.