Noninvasive Neural Imaging and Tissue Oxygenation in the Visual System

Noninvasive functional magnetic resonance imaging (fMRI) has become a primary tool for the measurement of behavior-related neural activity in the human brain. However, the blood oxygen level-dependent (BOLD) signal used in fMRI does not directly measure neural activity. It measures hemodynamic local changes in deoxygenated hemoglobin. To understand the functional significance of these changes, local tissue oxygen concentration may be measured as a way of studying dynamic oxygenation in the brain. Here, we use a dual-purpose sensor to simultaneously measure changes in tissue oxygenation and neural activity in the central visual pathway. We find that this technique can be used reliably in an in vivo section of a functioning visual system. Based on a series of experiments, we have attempted to answer the following questions. First, are there two major components, a small initial dip and a large positive peak, in tissue oxygen response as shown in fMRI and optical imaging studies? If there are two components, is one better coupled with neural activity? If the initial dip in tissue oxygenation is found, we wish to determine if it is unreliable as is the case in fMRI. Second, is tissue oxygen response coupled linearly with neural activity for temporal, spatial, and scaling domains? Third, can neurometabolic coupling be modified by activation of intracortical inhibitory networks? Finally, extracellular neural recordings may be specified in three major categories: single cell, multip...
Source: Springer protocols feed by Neuroscience - Category: Neuroscience Source Type: news