The Chapter Skim interface presents what we've algorithmically identified as the most significant single chunk of text within every page in the chapter.
Select key terms on the right to highlight them within pages of the chapter.
From page 173... ...
A reduction in local glucose and oxygen stimulates the brain to increase local arteriolar vasodilation, which increases local cerebral blood flow (CBF) and cerebral blood volume through a mechanism known as neurovascular coupling.
|
From page 174... ...
or fiber-optic bundles, and a light detector that receives light after it has interacted with tissue. Light scatters after entering tissue, and a photodetector placed 2-7 cm away from the optode, an optical sensor device that optically measures a specific substance usually with the aid of a chemical transducer, can collect light after it has passed through tissue.
|
From page 175... ...
. Despite current limitations, the fast optical signal continues to be an important subject of investigation because it offers glimpses of the "holy grail" of neuroimaging: the direct measurement of neuronal activity with millisecond resolution and superior spatial resolution.
|
From page 176... ...
CW spectroscopy applies continuous or slow-pulse (up to several kilohertz) light to tissue and measures the attenuation of amplitude of the incident light (Strangman et al., 2002; Hoshi, �������������������������������� 2003; Izzetoglu et al., 2004; Obrig and Villringer, 2003)
|
From page 177... ...
Therefore, fMRI, like fNIRS, is an indirect measure of neuronal activity that assesses changes in the concentration of deoxy-Hb in local tissue. There is no simple relationship between the magnitude of the signal change and any single physiological measure inasmuch as the magnitude relies on changes in blood flow, blood volume, and local oxygen tension.
|
From page 178... ...
Functional Specialization The human brain evolved in layers, with evolutionarily newer structures covering older ones. The developing brain in a human embryo grows outward in a pattern that largely mirrors human evolution.
|
From page 179... ...
If we factor in circuits that involve thousands or tens of thousands or even millions of reciprocal connections, it becomes clear that there are far more combinations of neural circuits in the cerebral cortex than atoms in the known universe. Cautious but undaunted, scientists are busily mapping the connectivity of the human brain in thousands of new papers published each year. Many studies are investigating correlations between traditional psychological testing, clinical observations, and brain scans to establish biomarkers of pathological states, cognitive and behavioral tasks, task-specific aptitude measures, detection of deception, and even prediction of neuropathological propensity.
|
From page 180... ...
1991. The development of a near infrared spectroscopy system and its application for non invasive monitoring of cerebral blood and tissue oxygenation in the newborn infant.
|
From page 181... ...
2004. Are VEP correlated fast optical signals detectable in the human adult by non-invasive near infrared spectroscopy (NIRS)
|
Key Terms
This material may be derived from roughly machine-read images, and so is provided only to facilitate research.
More
information on Chapter Skim is available.