PubMed Health⌕ Search
Home/Archive/PubMed

PubMed · 10571920

Perfusion-based event-related functional MRI.

H L Liu·J H Gao
View original source ↗Export metadata ↓

Abstract

Perfusion-based event-related functional MRI was performed by measuring flow-sensitive alternating inversion recovery (FAIR) signal changes during repeated single-trial, short visual stimulation (250 msec). In the visual cortex activation area, the blood flow increases immediately after the stimulus, reaches the maximum 4 sec later with a perfusion-sensitized signal change of 16. 1 +/- 2.6 %, and then decreases to baseline approximately 11 sec after the stimuli. As it is a more direct reflection of the hemodynamic response, perfusion-based event-related functional MRI techniques may be more useful for human cognitive function studies, compared with blood oxygenation level-dependent (BOLD)-based event-related functional MRI techniques. Magn Reson Med 42:1011-1013, 1999.

Explore related subjects

Cerebrovascular CirculationEcho-Planar ImagingHumansMagnetic Resonance ImagingPhotic StimulationVisual CortexJournal Article

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

H L Liu, J H Gao. 1999. Perfusion-based event-related functional MRI.. https://doi.org/10.1002/(sici)1522-2594(199912)42%3A6%3C1011%3A%3Aaid-mrm3%3E3.0.co%3B2-r

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related citations

PubMed2006

High frequency deep brain stimulation: what are the therapeutic mechanisms?

High frequency deep brain stimulation (HFS) used to treat the symptoms of Parkinson's disease (PD) was first assumed to act by reducing an excessive tonic GABAergic inhibitory output from the internal globus pallidus (GPi). Stimulation in GPi might produce this directly by mechanisms such as depolarization block or activation of presynaptic inhibitory fibers, and the same mechanisms evoked by HFS in the subthalamic nucleus (STN) could reduce the excitatory action of STN on GPi neurons. Although somatic recordings from neurons near the stimulation site may appear to support this potential mechanism, the action downstream from the site of stimulation often is not consistent with this interpretation. A more parsimonious explanation for the similar effects of HFS in STN or GPi and a lesion of either of these structures is that both HFS and pallidotomy interrupt an abnormal pattern of firing in cortico-basal ganglia-thalamocortical loops that is responsible for the symptoms of PD.

Cerebrovascular Circulation↗
PubMed2006

STN stimulation alters pallidal-frontal coupling during response selection under competition.

To investigate the effects of bilateral subthalamic nucleus (STN) stimulation on patterns of brain activation during random number generation (RNG), a task that requires suppression of habitual counting and response selection under competition. We used H(2)(15)O positron emission tomography to investigate the changes of regional cerebral blood flow (rCBF) induced by bilateral STN stimulation during a RNG task, in six patients with Parkinson's disease. Paced RNG at 1 Hz was compared with a control counting task. Both tasks were performed off medication with deep brain stimulation on and off. Subthalamic nucleus stimulation had a negative effect on performance of fast-paced RNG, leading to reduced randomness and increased habitual counting. Subthalamic nucleus stimulation also induced a reduction of rCBF in the left dorsal frontal gyrus, inferior frontal gyrus, dorsolateral prefrontal cortex, posterior and right anterior cingulate, and an increase of rCBF in the right internal globus pallidum (GPi) during RNG. Stimulation of the STN significantly altered pallidal coupling with frontal and temporal areas compared with when the stimulators were off. In conclusion, during RNG: (i) STN stimulation activates its output neurons to the GPi; (ii) STN stimulation induces increased inhibition of a prefrontal-cingulate network. This is the first direct evidence that STN stimulation significantly alters pallidal coupling with prefrontal, cingulate, and temporal cortices during performance of a task that requires response selection under competition.

Cerebrovascular Circulation↗
PubMed2006

Cerebral perfusion imaging in vasospasm.

Vasospasm following cerebral aneurysm rupture is one of the most devastating sequelae and the most common cause of delayed ischemic neurological deficit (DIND). Because vasospasm also is the most common cause of morbidity and mortality in patients who survive the initial bleeding episode, it is imperative not only to diagnose the condition but also to predict which patients are likely to become symptomatic. The exact pathophysiology of vasospasm is complex and incompletely elucidated. Early recognition of vasospasm is essential because the timely use of several therapeutic interventions can counteract this disease and prevent the occurrence of DIND. However, the prompt implementation of these therapies depends on the ability to predict impending vasospasm or to diagnose it at its early stages. A number of techniques have been developed during the past several decades to evaluate cerebral perfusion, including positron emission tomography, xenon-enhanced computed tomography, single-photon emission computed tomography, perfusion- and diffusion-weighted magnetic resonance imaging, and perfusion computed tomography. In this article, the authors provide a general overview of the currently available perfusion imaging techniques and their applications in treating vasospasm after a patient has suffered a subarachnoid hemorrhage. The use of cerebral perfusion imaging techniques for the early detection of vasospasm is becoming more common and may provide opportunities for early therapeutic intervention to counteract vasospasm in its earliest stages and prevent the occurrence of DINDs.

Cerebrovascular Circulation↗