Human Functional Brain Imaging Research Articles

S3 Non-invasive functional imaging of human brain

Measurements of the density and composition of the thermosphere between 150 and 500 km, which were obtained by the S3-1 satellite, have been compared with the Jacchia and MSIS models. The measurements of the densities of O, N2, N and Ar show some differences from the current models which should be considered during the preparation of the next CIRA model. The Ar measurements are particularly useful in examining the response of the neutral atmosphere to geomagnetic heating. These results are useful in establishing the appropriate lower boundary conditions for modeling of the thermosphere.

S3 Non-invasive functional imaging of human brain

S3 Non-invasive functional imaging of human brain

Human brain functional imaging with reflectance CWS.

Continuous Wave Spectroscopy (CWS) has been used in human subjects to detect brain function by observation of brain oxygenation and blood volume changes. In this research, we have developed a device for imaging brain oxygenation and blood volume with multiple sources and detectors in an area of 10 x 12 cm. Twelve, 1 watt tungsten bulbs were used as a light source, together with 8 detectors consisting of silicon-photodiodes with band-pass filters at 760 and 850 nms. The detectors were placed on a model system of the human head, providing 16 source-detector combinations with 4 cm separation. Eight to 16 seconds were required to image a brain function. Models using resin and a black object which have similar optical characteristics to a brain were studied. The model study showed that we can detect changes in absorption as deep as 2 cm from the surface. Human subjects with relatively thin hair, who volunteered for this study, were asked to tap fingers and rest, or to observe light flashing and darkness alternatively for 10 to 20 minutes while the images were being taken. In the finger tapping, the blood volume increased in a small, 1-2 cm area, while in the light stimulation, a much larger area was affected with a greater increased blood volume. Oxygenation occurred also in the area where blood volume increased. We concluded that the CWS can be used to image the location of brain activity by means of blood volume increase and oxygenation. In addition, brain disfunction and diseases, such as learning disability and brain hematoma may be detected with this imaging device.

Magnetic resonance imaging of human brain function

Previously the exclusive domain of the technology of positron emission tomography, functional MRI is now proving capable of mapping functional regions of the human cortex in near real time during specific task activations or in response to any hemodynamic stress. Of particular interest is the opportunity to observe secondary cortical responses, activation due to imagined tasks, memory function, time-resolved pathways through cortical regions, and activation in sub-cortical structures. One method of functional MRI uses blood oxygenation changes, which can be imaged continuously while functional centers are being stimulated. Image intensity can become darker if there is more deoxygenated blood and brighter if more oxygenated blood enters the brain. This concepts works in all perfused tissues in the body, and allows use of the blood oxygenation mechanism to image neuronal activation. A second method takes advantage of the fact that the protons within the MRI slice are always partially saturated by the rapid rate of imaging. As blood flow delivers unsaturated blood water protons into an imaged slice, these arterially-delivered protons will appear very bright in the image. Visualization of this effect is accomplished by simple image subtraction or by comparison of intensity changes as a function of the paradigm application frequency. Using either approach leads directly to a functional map. At present, clinical applications are rapidly moving toward routine non-invasive mapping of distortions of the functional motor and somatosensory cortex and other cortical regions as a result of brain tumors. Other clinical applications include the observation of the effect of degenerative diseases such as multiple sclerosis. Alzheimer's disease, stroke, migraine, epilepsy, and other diseases causing neuronal loss and Parkinsonism. Functional MRI and its applications will continue to grow exponentially throughout the decade.

S-H2-03 Imaging of human brain function with high magnetic fields: Kâmil Uǧurbil Center for Magnetic Resonance Research, Departments of Radiology, Medicine and Biochemistry, University of Minnesota, Minneapolis, MN

S-H2-03 Imaging of human brain function with high magnetic fields: Kâmil Uǧurbil Center for Magnetic Resonance Research, Departments of Radiology, Medicine and Biochemistry, University of Minnesota, Minneapolis, MN

Noninvasive near infrared optical imaging of human brain function with subsecond temporal resolution

Our understanding of human brain function can clearly benefit from neurophysiological techniques capable of providing dynamic maps of activity. A series of studies is reviewed indicating that noninvasive nearinfrared optical imaging methods can provide a unique combination of spatial and temporal resolution that could be used to derive dynamic maps of human brain activity. The noninvasive NIR optical data reviewed are based on the frequency-domain time-resolved measurement of photon migration parameters (intensity and delay) through brain tissue. These measurements are taken through the intact surface of the head. With these methods, two distinct components of the optical response can be identified: the ‘‘slow optical signal’’ (2–10 s latency), presumably due to hemodynamic and metabolic changes, and the ‘‘fast optical signal’’ (or event-related optical response) occurring as early as 50 to 100 ms from stimulation, and probably due to neuronal activation.

Effects of biophysical and physiologic parameters on brain activation‐induced R2* and R2 changes: Simulations using a deterministic diffusion model

AbstractA central issue in magnetic resonance imaging of human brain function using blood oxygenation level‐dependent (BOLD) contrast is the accurate interpretation of the signal changes that are observed. Using a method that incorporates repeated phase rotation and convolution with a smoothing function to simulate spin diffusion in the presence of magnetic field perturbers, the dependencies of the absolute and relative changes in transverse relaxation rates (δR2* and δR2) on biophysical and physiologic parameters were explored. First we introduce the modeling methodology. Then we simulate δR2* and δR2 as physiologic and biophysical parameters are modulated within the ranges that they vary across subjects and voxels in the brain. The simulations demonstrate that the δR2* and δR2 values that occur with activation‐induced changes in blood oxygenation depend most strongly on the resting state blood volume and field strength. The δR2*/δR2 ratios depend most strongly on the vessel radius and spin diffusion coefficient.

Magnetic resonance functional imaging of the brain at 4 t

Blood Oxygenation Level Dependent (BOLD) contrast imaging of human brain function using echo-planar imaging at 4 T gives good freedom from motion artifact, high signal-to-noise ratio/unit time, and adequate spatial resolution. Studies were made of brain activation associated with perceptual and cognitive tasks of several minutes duration.

463. MRI による脳機能画像(MR 脳機能画像-2)

通常用いられている臨床用MRI装置を用いて光刺激及び運動負荷に対して、脳機能画像としての信号変化を捉え得ることが可能であった。しかし、実際的な臨床応用には刺激方法の工夫、撮影条件の最適化(S/Nの向上)、画像処理等解決しなければならない多くの問題点がある。

Changes in neuron structure during action potential propagation and synaptic transmission.

Changes in neuron structure during action potential propagation and synaptic transmission.