Widespread and intense BOLD changes during brief focal electrographic seizures

Neurology ◽  
2006 ◽  
Vol 66 (7) ◽  
pp. 1049-1055 ◽  
Author(s):  
E. Kobayashi ◽  
C. S. Hawco ◽  
C. Grova ◽  
F. Dubeau ◽  
J. Gotman
Keyword(s):  
Blood Oxygenation Level Dependent ◽  
Blood Oxygenation ◽  
Angular Gyrus ◽  
Temporal Region ◽  
Bold Signal ◽  
Hemodynamic Response Function ◽  
Focal Seizures ◽  
Blood Oxygenation Level ◽  
Oxygenation Level ◽  
Electrographic Seizures

Background: Combined recording of EEG and fMRI has shown changes in blood oxygenation level dependent (BOLD) signal during focal interictal epileptic spikes. Due to difficult assessment of seizures inside the scanner little is known about BOLD changes during seizures.Objectives: To describe BOLD changes related to brief focal electrographic seizures in a patient with right temporo-parietal gray matter nodular heterotopia.Methods: The patient underwent two EEG-fMRI sessions during which several focal seizures were recorded. EEG was acquired continuously during scanning and seizure timing was used for statistical analysis. Functional maps were thresholded to disclose positive (activation) and negative (deactivation) BOLD changes.Results: Twenty-five focal electrographic seizures were analyzed, consisting of runs of polyspikes lasting 2 to 6 s in the right temporal region. Activation included a large volume, involving the heterotopia and the abnormal temporo-parietal cortex overlying the nodule, with a clear maximum over the angular gyrus. Deactivation was bilateral and maximum in the occipital regions. The hemodynamic response function showed a return to baseline of the BOLD signal 30 s after seizure end.Conclusions: The brief focal seizures resulted in high amplitude and widespread blood oxygenation level dependent (BOLD) responses taking 30 s to return to baseline. This suggests that such brief events could have important behavioral consequences despite absent overt manifestations. A clear focal BOLD peak was found at some distance from the main EEG discharge, raising the possibility that the seizure could have started in a region that did not generate a visible EEG change despite its superficial location.

Optogenetic fMRI Sheds Light on the Neural Basis of the BOLD Signal

2010 ◽  
Vol 104 (4) ◽  
pp. 1838-1840 ◽  
Author(s):  
Helen. S. Palmer
Keyword(s):  
Magnetic Resonance Imaging ◽  
Blood Oxygenation Level Dependent ◽  
Blood Oxygenation ◽  
Bold Signal ◽  
Functional Magnetic Resonance ◽  
Resonance Imaging ◽  
Neural Basis ◽  
Bold Responses ◽  
Blood Oxygenation Level ◽  
Oxygenation Level

Blood oxygenation level dependent (BOLD) functional magnetic resonance imaging (fMRI) is widely used as a measure of neuronal activity, despite an incomplete understanding of the hemodynamic and neural bases for BOLD signals. Recent work by Lee and colleagues investigated whether activating genetically specified neurons elicits BOLD responses. Integrating optogenetic control of specific cells and fMRI showed that stimulating excitatory neurons triggers a positive BOLD signal with conventional kinetics locally and delayed weaker BOLD signals distally.

scholarly journals Simultaneous Blood Oxygenation Level-Dependent and Cerebral Blood Flow Functional Magnetic Resonance Imaging during Forepaw Stimulation in the Rat

1999 ◽  
Vol 19 (8) ◽  
pp. 871-879 ◽  
Author(s):  
Afonso C. Silva ◽  
Sang-Pil Lee ◽  
Guang Yang ◽  
Costantino Iadecola ◽  
Seong-Gi Kim
Keyword(s):  
Correlation Coefficient ◽  
Cerebral Blood Volume ◽  
Blood Oxygenation Level Dependent ◽  
Blood Oxygenation ◽  
Single Shot ◽  
Bold Signal ◽  
Doppler Flowmetry ◽  
Blood Oxygenation Level ◽  
Oxygenation Level ◽  
Signal Changes

The blood oxygenation level-dependent (BOLD) contrast mechanism can be modeled as a complex interplay between CBF, cerebral blood volume (CBV), and CMRO2. Positive BOLD signal changes are presumably caused by CBF changes in excess of increases in CMRO2. Because this uncoupling between CBF and CMRO2 may not always be present, the magnitude of BOLD changes may not be a good index of CBF changes. In this study, the relation between BOLD and CBF was investigated further. Continuous arterial spin labeling was combined with a single-shot, multislice echo-planar imaging to enable simultaneous measurements of BOLD and CBF changes in a well-established model of functional brain activation, the electrical forepaw stimulation of a-chloralose-anesthetized rats. The paradigm consisted of two 18- to 30-second stimulation periods separated by a 1-minute resting interval. Stimulation parameters were optimized by laser Doppler flowmetry. For the same cross-correlation threshold, the BOLD and CBF active maps were centered within the size of one pixel (470 µm). However, the BOLD map was significantly larger than the CBF map. Measurements taken from 15 rats at 9.4 T using a 10-millisecond echo-time showed 3.7 ± 1.7% BOLD and 125.67 ± 81.7% CBF increases in the contralateral somatosensory cortex during the first stimulation, and 2.6 ± 1.2% BOLD and 79.3 ± 43.6% CBF increases during the second stimulation. The correlation coefficient between BOLD and CBF changes was 0.89. The overall temporal correlation coefficient between BOLD and CBF time-courses was 0.97. These results show that under the experimental conditions of the current study, the BOLD signal changes follow the changes in CBF.

scholarly journals Origin of Negative Blood Oxygenation Level—Dependent fMRI Signals

2002 ◽  
Vol 22 (8) ◽  
pp. 908-917 ◽  
Author(s):  
Noam Harel ◽  
Sang-Pil Lee ◽  
Tsukasa Nagaoka ◽  
Dae-Shik Kim ◽  
Seong-Gi Kim
Keyword(s):  
Neural Activity ◽  
Spike Activity ◽  
Visual Stimulation ◽  
Blood Oxygenation Level Dependent ◽  
Blood Oxygenation ◽  
Bold Signal ◽  
Area 18 ◽  
Blood Oxygenation Level ◽  
Oxygenation Level ◽  
Negative Bold

Functional magnetic resonance imaging (fMRI) techniques are based on the assumption that changes in spike activity are accompanied by modulation in the blood oxygenation level—dependent (BOLD) signal. In addition to conventional increases in BOLD signals, sustained negative BOLD signal changes are occasionally observed and are thought to reflect a decrease in neural activity. In this study, the source of the negative BOLD signal was investigated using T2*-weighted BOLD and cerebral blood volume (CBV) techniques in isoflurane-anesthetized cats. A positive BOLD signal change was observed in the primary visual cortex (area 18) during visual stimulation, while a prolonged negative BOLD change was detected in the adjacent suprasylvian gyrus containing higher-order visual areas. However, in both regions neurons are known to increase spike activity during visual stimulation. The positive and negative BOLD amplitudes obtained at six spatial-frequency stimuli were highly correlated, and negative BOLD percent changes were approximately one third of the postitive changes. Area 18 with positive BOLD signals experienced an increase in CBV, while regions exhibiting the prolonged negative BOLD signal underwent a decrease in CBV. The CBV changes in area 18 were faster than the BOLD signals from the same corresponding region and the CBV changes in the suprasylvian gyrus. The results support the notion that reallocation of cortical blood resources could overcome a local demand for increased cerebral blood flow induced by increased neural activity. The findings of this study imply that caution should be taken when interpreting the negative BOLD signals as a decrease in neuronal activity.

scholarly journals Quantitative aspects of brain perfusion dynamic induced by BOLD fMRI

2006 ◽  
Vol 64 (4) ◽  
pp. 895-898 ◽  
Author(s):  
Katia C. Andrade ◽  
Octavio M. Pontes-Neto ◽  
Joao P. Leite ◽  
Antonio Carlos Santos ◽  
Oswaldo Baffa ◽  
...  
Keyword(s):  
Blood Flow ◽  
Grey Matter ◽  
Brain Perfusion ◽  
Blood Oxygenation Level Dependent ◽  
Blood Oxygenation ◽  
Breath Holding ◽  
Bold Signal ◽  
Blood Oxygenation Level ◽  
Oxygenation Level ◽  
Dependent Signal

The increase of relative cerebral blood flow (rCBF) may contribute for a change in blood oxygenation level dependent signal (BOLD). The main purpose of this study is to investigate some aspects of perfusional alterations in the human brain in response to a uniform stimulation: hypercapnia induced by breath holding. It was observed that the BOLD signal increased globally during hypercapnia and that it is correlated with the time of breath holding. This signal increase shows a clear distinction between gray and white matter, being greater in the grey matter.

scholarly journals Syntactic and Thematic Constraint Effects on Blood Oxygenation Level Dependent Signal Correlates of Comprehension of Relative Clauses

2008 ◽  
Vol 20 (4) ◽  
pp. 643-656 ◽  
Author(s):  
David Caplan ◽  
Louise Stanczak ◽  
Gloria Waters
Keyword(s):  
Relative Clauses ◽  
Syntactic Structure ◽  
Blood Oxygenation Level Dependent ◽  
Blood Oxygenation ◽  
Bold Signal ◽  
Thematic Roles ◽  
Middle Temporal ◽  
Blood Oxygenation Level ◽  
Oxygenation Level ◽  
Left Middle

The effects of plausibility of thematic role assignment and syntactic structure on blood oxygenation level dependent (BOLD) signal were studied using event-related functional magnetic resonance imaging by orthogonally varying syntactic structure (subject-vs. object-extracted relative clauses) and the plausibility of nouns playing thematic roles (constrained vs. unconstrained sentences) in a plausibility judgment task. In plausible sentences, BOLD signal increased for object-compared to subject-extracted clauses in unconstrained sentences in left middle temporal and left inferior frontal areas, for this contrast in constrained sentences in left middle temporal but not left inferior frontal areas, and for constrained subject-extracted sentences compared to unconstrained subject-extracted sentences in the left inferior frontal gyrus and the left dorsolateral prefrontal cortex. We relate these areas of activation to the assignment of the syntactic structure of object-compared to subject-extracted structures and the process of checking which thematic roles activated in the course of processing a sentence are licensed by the syntactic structure of the sentence.

scholarly journals BOLD-Perfusion Coupling during Monocular and Binocular Stimulation

2008 ◽  
Vol 2008 ◽  
pp. 1-6 ◽  
Author(s):  
Claudine Gauthier ◽  
Richard D. Hoge
Keyword(s):  
Visual Cortex ◽  
Oxidative Metabolism ◽  
Visual Stimulation ◽  
Blood Oxygenation Level Dependent ◽  
Blood Oxygenation ◽  
Bold Signal ◽  
Blood Oxygenation Level ◽  
Monocular Stimulation ◽  
Binocular Stimulation ◽  
Oxygenation Level

Previous studies have suggested that during selective activation of a subset of the zones comprising a columnar system in visual cortex, perfusion increases uniformly in all columns of the system, while increases in oxidative metabolism occur predominantly in the activated columns. This could lead to disproportionately large blood oxygenation level-dependent (BOLD) signal increases for a given flow increase during monocular (relative to binocular) stimulation, due to contributions from columns which undergo large increases in perfusion with little or no change in oxidative metabolism. In the present study, we sought to test this hypothesis by measuring BOLD-perfusion coupling ratios in spatially averaged signals over V1 during monocular and binocular visual stimulation. It was found that, although withholding input to one eye resulted in statistically significant decreases in BOLD and perfusion signals in primary visual cortex, the ratio between BOLD and perfusion increases did not change significantly. These results do not support a gross mismatch between spatial patterns of flow and metabolism response during monocular stimulation.

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