News | June 29, 2008

New Research Opens Eyes to Understanding Brain Imaging

June 30, 2008 – New research from Harvard University neuroscientists has pinpointed exactly how neural activity boosts blood flow to the brain, helping to better understand brain imaging techniques such as fMRI.

The research is described in the June 26 issue of the journal Neuron.

"When you see a brain image from fMRI studies, you are actually looking at changes in blood flow and oxygenation," says Venkatesh N. Murthy, professor of molecular and cellular biology in Harvard's Faculty of arts and sciences. "But because of the tight coupling between neural activity and blood flow, we are able to use the blood flow changes as a surrogate for brain activity. A better understanding of exactly how brain activity boosts blood flow should help us better read this process in reverse, which is what we do when interpreting fMRI images."

While it represents only about five percent of the human body's mass, the brain consumes 20 percent of the oxygen carried in its blood. Unlike muscle and other types of tissue, the brain has no internal energy stores, so all its metabolic needs must be met through the continuous flow of blood.

Murthy and colleagues studied mice and found that neurovascular coupling occurs through intermediary cells called astrocytes. By manipulating calcium levels, astrocytes can dilate or constrict blood vessels, depending on whether or not the cells are bound by neurotransmitters.

When a region of the brain becomes active, neurotransmitters begin to trickle out of that area's neural circuitry. The most common of these neurotransmitters in the mammalian brain, glutamate, is widely released at synapses and binds to astrocytes as well as to postsynaptic receptors. Murthy's group found that after binding glutamate, astrocytes elevate their intracellular calcium levels, dilating blood vessels and increasing blood flow to that region of the nervous system.

Murthy and colleagues studied this process in the olfactory bulb, which processes odors.

"When a mouse encounters a scent, discrete loci in its olfactory bulb are activated, which in turn increases blood flow in those spots," Murthy says. "We measured all this using sophisticated optical microscopy, actually counting the number and rate of red blood cells passing through capillaries in the area. In addition to showing directly that astrocytes are involved in neurovascular coupling, we discovered that there are multiple molecular signaling pathways involved."

The new research by Murthy and colleagues lays the groundwork for further study of how this exquisite neurovascular coupling may go awry in neurodegenerative diseases, such as Alzheimer's disease, as well as in the normally aging brain. A growing body of evidence suggests that as people age -- and especially with the onset of neurodegenerative disease -- neurovascular coupling can be impaired. It's still unknown whether this impairment can add to the cognitive defects associated with both healthy and diseased aging.

For more information: www.harvard.edu

Related Content

Youth Football Changes Nerve Fibers in Brain

Statistically significant clusters (red-colored) showing group differences (Control vs. Football) in white matter strain along the primary (F1) and secondary (F2) fibers. While body of corpus callosum (BBC) showed relative shrinkage in Football group, the other clusters showed relative stretching of fibers. PCR: Posterior Corona Radiata, PLIC: Posterior Limb of Internal Capsule, SCR: Superior Corona Radiata, SLF: Superior Longitudinal Fasciculus, SCC: Splenium of Corpus Callosum. Image courtesy of Kim et al.

News | Neuro Imaging | December 07, 2018
Magnetic resonance imaging (MRI) scans show repetitive blows to the head result in brain changes among youth football...
Siemens Healthineers Debuts Magnetom Altea 1.5T MRI Scanner
Technology | Magnetic Resonance Imaging (MRI) | December 06, 2018
During the 104th Scientific Assembly and Annual Meeting of the Radiological Society of North America (RSNA), Nov. 25-30...
GE Healthcare Unveils New Applications and Smart Devices Built on Edison Platform
Technology | Artificial Intelligence | December 05, 2018
GE Healthcare recently announced new applications and smart devices built on Edison – a platform that helps accelerate...
Snoring Poses Greater Cardiac Risk to Women
News | Women's Health | November 29, 2018
Obstructive sleep apnea (OSA) and snoring may lead to earlier impairment of cardiac function in women than in men,...
Vital Showcases Enterprise Imaging Advances at RSNA 2018

Global Illumination from Vital Images

News | Enterprise Imaging | November 28, 2018
Vital, a Canon Group company, will highlight the latest additions to its enterprise imaging portfolio at the 2018...
Artificial Intelligence May Help Reduce Gadolinium Dose in MRI

Example of full-dose, 10 percent low-dose and algorithm-enhanced low-dose. Image courtesy of Enhao Gong, Ph.D.

News | Contrast Media | November 27, 2018
Researchers are using artificial intelligence (AI) to reduce the dose of a contrast agent that may be left behind in...
Arterys Demonstrates AI Cloud-Based Medical Image Analysis Solutions at RSNA 2018
News | Computer-Aided Detection Software | November 26, 2018
Medical imaging software company Arterys will demonstrate its wide-ranging suite of artificial intelligence (AI)-...
HeartVista Announces One Click Autonomous MRI Solution
News | Magnetic Resonance Imaging (MRI) | November 25, 2018
HeartVista announced its artificial intelligence (AI)-driven, One-Click Autonomous MRI acquisition software for cardiac...
Siemens Healthineers Showcases syngo Virtual Cockpit for More Flexible Workforce Management
News | Teleradiology | November 25, 2018
During the 104th Scientific Assembly and Annual Meeting of the Radiological Society of North America (RSNA), Nov. 25-30...
Canon Medical Receives FDA Clearance for Vantage Orian 1.5T MRI
Technology | Magnetic Resonance Imaging (MRI) | November 15, 2018
Canon Medical Systems USA Inc. received 510(k) clearance from the U.S. Food and Drug Administration (FDA) on its new...