scholarly journals BRIDGING THE GAP BETWEEN NEUROIMAGING AND NEURONAL PHYSIOLOGY

2011 ◽  
Vol 21 (2) ◽  
pp. 97 ◽  
Author(s):  
Dae-Shik Kim ◽  
Kamil Ugurbil
Keyword(s):  
Functional Mri ◽  
Functional Neuroimaging ◽  
Explanatory Power ◽  
Blood Oxygenation ◽  
Functional Magnetic Resonance ◽  
Neural Correlate ◽  
Neuroimaging Data ◽  
Oxygenation Level ◽  
Spatial Specificity ◽  
Neuronal Physiology

Despite the fact that blood oxygenation level dependent (BOLD) functional magnetic resonance imaging (fMRI) studies have become ubiquitous and are of ever increasing importance for clinical and basic neurosciences, the fundamental relationships between BOLD and the underlying neuronal physiology are not understood. This raises severe concerns about the validity of BOLD contrast per se, and the conceptual frameworks currently employed in interpreting cognitive neuroimaging data. In order to expand the explanatory power of functional MRI data, several crucial questions will have to be addressed. The two most important questions are: First, what is the ultimate spatial resolution of fMRI?, secondly, what is the "neural correlate" of functional MRI? This article attempts to compile a series of results from our and other laboratories, suggesting that both the questions of "spatial specificity" and "neural correlate" might be within the reach of a tentative solution, thus finally bridging the gap between functional neuroimaging and neuronal physiology.

scholarly journals Time-dependent spatial specificity of high-resolution fMRI: insights into mesoscopic neurovascular coupling

2020 ◽  
Vol 376 (1815) ◽  
pp. 20190623
Author(s):  
Mitsuhiro Fukuda ◽  
Alexander J. Poplawsky ◽  
Seong-Gi Kim
Keyword(s):  
High Resolution ◽  
Neuronal Activity ◽  
Cerebral Blood Volume ◽  
Functional Neuroimaging ◽  
Neurovascular Coupling ◽  
Blood Oxygenation ◽  
Non Invasive ◽  
True Location ◽  
Oxygenation Level ◽  
Spatial Specificity

High-resolution functional magnetic resonance imaging (fMRI) is becoming increasingly popular because of the growing availability of ultra-high magnetic fields which are capable of improving sensitivity and spatial resolution. However, it is debatable whether increased spatial resolutions for haemodynamic-based techniques, like fMRI, can accurately detect the true location of neuronal activity. We have addressed this issue in functional columns and layers of animals with haemoglobin-based optical imaging and different fMRI contrasts, such as blood oxygenation level-dependent, cerebral blood flow and cerebral blood volume fMRI. In this review, we describe empirical evidence primarily from our own studies on how well these fMRI signals are spatially specific to the neuronally active site and discuss insights into neurovascular coupling at the mesoscale. This article is part of the theme issue ‘Key relationships between non-invasive functional neuroimaging and the underlying neuronal activity’.

Attenuated Brain Response to Auditory Word Stimulation with Sevoflurane

2005 ◽  
Vol 103 (1) ◽  
pp. 11-19 ◽  
Author(s):  
Chantal Kerssens ◽  
Stephan Hamann ◽  
Scott Peltier ◽  
Xiaoping P. Hu ◽  
Michael G. Byas-Smith ◽  
...  
Keyword(s):  
Magnetic Resonance Imaging ◽  
Occipital Cortex ◽  
Blood Oxygenation Level Dependent ◽  
Blood Oxygenation ◽  
Functional Magnetic Resonance ◽  
Resonance Imaging ◽  
Brain Response ◽  
Auditory Word ◽  
Blood Oxygenation Level ◽  
Oxygenation Level

Background Functional magnetic resonance imaging offers a compelling, new perspective on altered brain function but is sparsely used in studies of anesthetic effect. To examine effects on verbal memory encoding, the authors imaged human brain response to auditory word stimulation using functional magnetic resonance imaging at different concentrations of an agent not previously studied, and tested memory after recovery. Methods Six male volunteers were studied breathing 0.0, 2.0, and 1.0% end-tidal sevoflurane (awake, deep, and light states, respectively) via laryngeal mask. In each condition, they heard 15 two-syllable English nouns via closed headphones. Each word was repeated 15 times (1/s), followed by 15 s of rest. Blood oxygenation level-dependent brain activations during blocks of stimulation versus rest were assessed with a 3-T Siemens Trio scanner and a 20-voxel spatial extent threshold. Memory was tested approximately 1.5 h after recovery with an auditory recognition task (chance performance = 33% correct). Results Scans showed widespread activations (P < 0.005, uncorrected) in the awake state, including bilateral superior temporal, frontal, and parietal cortex, right occipital cortex, bilateral thalamus, striatum, hippocampus, and cerebellum; more limited activations in the light state (bilateral superior temporal gyrus, right thalamus, bilateral parietal cortex, left frontal cortex, and right occipital cortex); and no significant auditory-related activation in the deep state. During recognition testing, subjects correctly selected 77 +/- 12% of words presented while they were awake as "old," versus 32 +/- 15 and 42 +/- 8% (P < 0.01) correct for the light and deep stages, respectively. Conclusions Sevoflurane induces dose-dependent suppression of auditory blood oxygenation level-dependent signals, which likely limits the ability of words to be processed during anesthesia and compromises memory.

scholarly journals Greater BOLD Variability is Associated With Poorer Cognitive Function in an Adult Lifespan Sample

2020 ◽  
Vol 31 (1) ◽  
pp. 562-574
Author(s):  
Maria A Boylan ◽  
Chris M Foster ◽  
Ekarin E Pongpipat ◽  
Christina E Webb ◽  
Karen M Rodrigue ◽  
...  
Keyword(s):  
Healthy Aging ◽  
Blood Oxygenation ◽  
Functional Magnetic Resonance ◽  
Resonance Imaging ◽  
Adult Lifespan ◽  
Age Related ◽  
Oxygenation Level ◽  
Linear Slope ◽  
Subcortical Regions ◽  
Effects Of Aging

Abstract Moment-to-moment fluctuations in brain signal assessed by functional magnetic resonance imaging blood oxygenation level dependent (BOLD) variability is increasingly thought to represent important “signal” rather than measurement-related “noise.” Efforts to characterize BOLD variability in healthy aging have yielded mixed outcomes, demonstrating both age-related increases and decreases in BOLD variability and both detrimental and beneficial associations. Utilizing BOLD mean-squared-successive-differences (MSSD) during a digit n-back working memory (WM) task in a sample of healthy adults (aged 20–94 years; n = 171), we examined effects of aging on whole-brain 1) BOLD variability during task (mean condition MSSD across 0–2–3-4 back conditions), 2) BOLD variability modulation to incrementally increasing WM difficulty (linear slope from 0–2–3-4 back), and 3) the association of age-related differences in variability with in- and out-of-scanner WM performance. Widespread cortical and subcortical regions evidenced increased mean variability with increasing age, with no regions evidencing age-related decrease in variability. Additionally, posterior cingulate/precuneus exhibited increased variability to WM difficulty. Notably, both age-related increases in BOLD variability were associated with significantly poorer WM performance in all but the oldest adults. These findings lend support to the growing corpus suggesting that brain-signal variability is altered in healthy aging; specifically, in this adult lifespan sample, BOLD-variability increased with age and was detrimental to cognitive performance.

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