scholarly journals Dynamic fMRI and EEG Recordings during Spike-Wave Seizures and Generalized Tonic-Clonic Seizures in WAG/Rij Rats

2004 ◽  
Vol 24 (6) ◽  
pp. 589-599 ◽  
Author(s):  
Hrachya Nersesyan ◽  
Fahmeed Hyder ◽  
Douglas L. Rothman ◽  
Hal Blumenfeld
Keyword(s):  
Somatosensory Cortex ◽  
Neuronal Activity ◽  
Epileptic Seizures ◽  
Occipital Cortex ◽  
Blood Oxygen Level Dependent ◽  
Blood Oxygen Level ◽  
Electrophysiological Recordings ◽  
Clonic Seizures ◽  
Eeg Recordings ◽  
Spike Wave

Generalized epileptic seizures produce widespread physiological changes in the brain. Recent studies suggest that “generalized” seizures may not involve the whole brain homogeneously. For example, electrophysiological recordings in WAG/Rij rats, an established model of human absence seizures, have shown that spike-and-wave discharges are most intense in the perioral somatosensory cortex and thalamus, but spare the occipital cortex. Is this heterogeneous increased neuronal activity matched by changes in local cerebral blood flow sufficient to meet or exceed cerebral oxygen consumption? To investigate this, we performed blood oxygen level-dependent functional magnetic resonance imaging (fMRI) measurements at 7T with simultaneous electroencephalogram recordings. During spontaneous spike-wave seizures in WAG/Rij rats under fentanylhaloperidol anesthesia, we found increased fMRI signals in focal regions including the perioral somatosensory cortex, known to be intensely involved during seizures, whereas the occipital cortex was spared. For comparison, we also studied bicuculline-induced generalized tonic-clonic seizures under the same conditions, and found fMRI increases to be larger and more widespread than during spike-and-wave seizures. These findings suggest that even in regions with intense neuronal activity during epileptic seizures, oxygen delivery exceeds metabolic needs, enabling fMRI to be used for investigation of dynamic cortical and subcortical network involvement in this disorder.

scholarly journals Saccadic Suppression Induces Focal Hypooxygenation in the Occipital Cortex

2000 ◽  
Vol 20 (7) ◽  
pp. 1103-1110 ◽  
Author(s):  
Rüdiger Wenzel ◽  
Petra Wobst ◽  
Hauke H. Heekeren ◽  
Kenneth K. Kwong ◽  
Stephan A. Brandt ◽  
...  
Keyword(s):  
Visual Cortex ◽  
Neuronal Activity ◽  
Near Infrared ◽  
Occipital Cortex ◽  
Blood Oxygen Level Dependent ◽  
Blood Oxygenation ◽  
Saccadic Suppression ◽  
Blood Oxygen Level ◽  
Behavioral Evidence ◽  
Cerebral Blood Oxygenation

This study investigated how a decrease in neuronal activity affects cerebral blood oxygenation employing a paradigm of acoustically triggered saccades in complete darkness. Known from behavioral evidence as saccadic suppression, electrophysiologically it has been shown in monkeys that during saccades an attenuation of activity occurs in visual cortex neurons ( Duffy and Burchfiel, 1975 ). In study A, using blood oxygen level-dependent (BOLD) contrast functional magnetic resonance imaging (fMRI), the authors observed signal intensity decreases bilaterally at the occipital pole during the performance of saccades at 2 Hz. In study B.1, the authors directly measured changes in deoxyhemoglobin [deoxy-Hb] and oxyhemoglobin [oxy-Hb] concentration in the occipital cortex with near-infrared spectroscopy (NIRS). Whereas a rise in [deoxy-Hb] during the performance of saccades occurred, there was a drop in [oxy-Hb]. In a second NIRS study (B.2), subjects performed saccades at different rates (1.6, 2.0, and 2.3 Hz). Here the authors found the increase in deoxy-Hb and the decrease of oxy-Hb to be dependent on the frequency of the saccades. In summary, the authors observed a focal hypooxygenation in the human visual cortex dependent on the saccade-frequency in an acoustically triggered saccades paradigm. This could be interpreted as evidence that corresponding to the focal hyperoxygenation observed in functional brain activation, caused by an excessive increase in cerebral blood flow (CBF) over the increase in CMRO2 during decreased neuronal activity CBF, is more reduced than oxygen delivery.

Equal Degrees of Object Selectivity for Upper and Lower Visual Field Stimuli

2010 ◽  
Vol 104 (4) ◽  
pp. 2075-2081 ◽  
Author(s):  
Lars Strother ◽  
Adrian Aldcroft ◽  
Cheryl Lavell ◽  
Tutis Vilis
Keyword(s):  
Visual Field ◽  
Occipital Cortex ◽  
Recognition System ◽  
Blood Oxygen Level Dependent ◽  
Lower Visual Field ◽  
Blood Oxygen Level ◽  
Visual Areas ◽  
Bold Responses ◽  
Cortical Regions ◽  
Lateral Occipital Cortex

Functional MRI (fMRI) studies of the human object recognition system commonly identify object-selective cortical regions by comparing blood oxygen level–dependent (BOLD) responses to objects versus those to scrambled objects. Object selectivity distinguishes human lateral occipital cortex (LO) from earlier visual areas. Recent studies suggest that, in addition to being object selective, LO is retinotopically organized; LO represents both object and location information. Although LO responses to objects have been shown to depend on location, it is not known whether responses to scrambled objects vary similarly. This is important because it would suggest that the degree of object selectivity in LO does not vary with retinal stimulus position. We used a conventional functional localizer to identify human visual area LO by comparing BOLD responses to objects versus scrambled objects presented to either the upper (UVF) or lower (LVF) visual field. In agreement with recent findings, we found evidence of position-dependent responses to objects. However, we observed the same degree of position dependence for scrambled objects and thus object selectivity did not differ for UVF and LVF stimuli. We conclude that, in terms of BOLD response, LO discriminates objects from non-objects equally well in either visual field location, despite stronger responses to objects in the LVF.

scholarly journals Rapid development of strong, persistent, spatiotemporally extensive cortical synchrony and underlying oscillations following acute MCA focal ischemia

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Ellen G. Wann ◽  
Anirudh Wodeyar ◽  
Ramesh Srinivasan ◽  
Ron D. Frostig
Keyword(s):  
Neuronal Activity ◽  
Rat Model ◽  
Microelectrode Array ◽  
Rapid Development ◽  
Similar Frequency ◽  
Electrophysiological Recordings ◽  
Ischemic Period ◽  
Spatiotemporal Analyses ◽  
Eeg Recordings ◽  
Evoked Activity

AbstractStroke is a leading cause of death and the leading cause of long-term disability, but its electrophysiological basis is poorly understood. Characterizing acute ischemic neuronal activity dynamics is important for understanding the temporal and spatial development of ischemic pathophysiology and determining neuronal activity signatures of ischemia. Using a 32-microelectrode array spanning the depth of cortex, electrophysiological recordings generated for the first time a continuous spatiotemporal profile of local field potentials (LFP) and multi-unit activity (MUA) before (baseline) and directly after (0–5 h) distal, permanent MCA occlusion (pMCAo) in a rat model. Although evoked activity persisted for hours after pMCAo with minor differences from baseline, spatiotemporal analyses of spontaneous activity revealed that LFP became spatially and temporally synchronized regardless of cortical depth within minutes after pMCAo and extended over large parts of cortex. Such enhanced post-ischemic synchrony was found to be driven by increased bursts of low multi-frequency oscillations and continued throughout the acute ischemic period whereas synchrony measures minimally changed over the same recording period in surgical sham controls. EEG recordings of a similar frequency range have been applied to successfully predict stroke damage and recovery, suggesting clear clinical relevance for our rat model.

scholarly journals Finger representations in primary somatosensory cortex are modulated during vibrotactile working memory

2021 ◽  
Author(s):  
Finn Rabe ◽  
Sanne Kikkert ◽  
Nicole Wenderoth
Keyword(s):  
Working Memory ◽  
Somatosensory Cortex ◽  
Pattern Analysis ◽  
Blood Oxygen Level Dependent ◽  
Brain Regions ◽  
Delay Period ◽  
Blood Oxygen Level ◽  
Secondary Somatosensory Cortex ◽  
Analysis Technique ◽  
Hand Area

It is well-established that vibrotactile stimulations elicit Blood-oxygen-level-dependent (BOLD) responses in somatotopically organized brain regions. Whether these somatotopic maps are modulated by working memory (WM) is still unknown. In our WM experiment, participants had to compare frequencies that were separated by a delay period. Vibrotactile stimuli were sequentially applied to either their right index or little finger. Using functional MRI, we investigated whether vibrotactile WM modulated neural activity in primary somatosensory (S1), an area that is known to contain individual finger representations. Our mass-univariate results revealed the well-described network of brain regions involved in WM. Interestingly, our mass-univariate results did not demonstrate S1 to be part of this network. However, when we parametrically modulated the time-binned regressors in our GLM we found that the delay activity in S1 and secondary somatosensory cortex (S2) was reflected in a U-shaped manner. Using multi-voxel pattern analysis (MVPA), an analysis technique that is more sensitive to subtle activity differences, we found finger-specific patterns of activation in the S1 hand area during the WM delay period. These results indicate that processes underlying WM modulate finger-specific representations during our discrimination task.

Increased regional homogeneity of blood oxygen level-dependent signals in occipital cortex of early blind individuals

Neuroreport ◽  
2011 ◽  
Vol 22 (4) ◽  
pp. 190-194 ◽  
Author(s):  
Chong Liu ◽  
Yong Liu ◽  
Weilan Li ◽  
Dawei Wang ◽  
Tianzi Jiang ◽  
...  
Keyword(s):  
Occipital Cortex ◽  
Blood Oxygen Level Dependent ◽  
Regional Homogeneity ◽  
Blood Oxygen ◽  
Oxygen Level ◽  
Blood Oxygen Level ◽  
Blind Individuals

scholarly journals Two distinct profiles of fMRI and neurophysiological activity elicited by acetylcholine in visual cortex

2018 ◽  
Vol 115 (51) ◽  
pp. E12073-E12082 ◽  
Author(s):  
Daniel Zaldivar ◽  
Alexander Rauch ◽  
Nikos K. Logothetis ◽  
Jozien Goense
Keyword(s):  
Visual Cortex ◽  
Injection Site ◽  
Blood Oxygen Level Dependent ◽  
Local Injection ◽  
Electrode Arrays ◽  
Blood Oxygen Level ◽  
Neural Signals ◽  
Electrophysiological Recordings ◽  
High Gamma ◽  
Neurophysiological Activity

Cholinergic neuromodulation is involved in all aspects of sensory processing and is crucial for processes such as attention, learning and memory, etc. However, despite the known roles of acetylcholine (ACh), we still do not how to disentangle ACh contributions from sensory or task-evoked changes in functional magnetic resonance imaging (fMRI). Here, we investigated the effects of local injection of ACh on fMRI and neural signals in the primary visual cortex (V1) of anesthetized macaques by combining pharmaco-based MRI (phMRI) with electrophysiological recordings, using single electrodes and electrode arrays. We found that local injection of ACh elicited two distinct profiles of fMRI and neurophysiological activity, depending on the distance from the injector. Near the injection site, we observed an increase in the baseline blood oxygen-level-dependent (BOLD) and cerebral blood flow (CBF) responses, while their visual modulation decreased. In contrast, further from the injection site, we observed an increase in the visually induced BOLD and CBF modulation without changes in baseline. Neurophysiological recordings suggest that the spatial correspondence between fMRI responses and neural activity does not change in the gamma, high-gamma, and multiunit activity (MUA) bands. The results near the injection site suggest increased inhibitory drive and decreased metabolism, contrasting to the far region. These changes are thought to reflect the kinetics of ACh and its metabolism to choline.

scholarly journals Electrochemical carbon fiber-based technique for simultaneous recordings of brain tissue PO2, pH, and extracellular field potentials

2020 ◽  
Author(s):  
Patrick S. Hosford ◽  
Jack A. Wells ◽  
Isabel N. Christie ◽  
Mark Lythgoe ◽  
Julian Millar ◽  
...  
Keyword(s):  
Carbon Fiber ◽  
Brain Tissue ◽  
Electrochemical Detection ◽  
Neuronal Activity ◽  
Blood Oxygen Level Dependent ◽  
Blood Oxygen Level ◽  
Carbon Fiber Electrodes ◽  
Tissue Po2 ◽  
Fast Cyclic Voltammetry

AbstractA method for simultaneous electrochemical detection of brain tissue PO2 (PtO2) and pH changes together with neuronal activity using a modified form of fast cyclic voltammetry with carbon fiber electrodes is described. This technique has been developed for in vivo applications and recordings from discrete brain nuclei in experimental animals. The small size of the carbon fiber electrode (⍰7μm, length <100μm) ensures minimal disruption of the brain tissue and allows recordings from small brain areas. Sample rate (up to 4 Hz) is sufficient to resolve rapid changes in PtO2 and pH that follow changes in neuronal activity and metabolism. Rapid switching between current and voltage recordings allows combined electrochemical detection and monitoring of extracellular action potentials. For simultaneous electrochemical detection of PtO2 and pH, two consecutive trapezoidal voltage ramps are applied with double differential-subtraction of the background current. This enables changes in current caused by protons and oxygen to be detected separately with minimal interference between the two. The profile of PtO2 changes evoked by increases in local neuronal activity recorded using the described technique was similar to that of blood oxygen level dependent responses recorded using fMRI. This voltammetric technique can be combined with fMRI and brain vessel imaging to study the metabolic mechanisms underlying neurovascular coupling response with much greater spatial and temporal resolution than is currently possible.

scholarly journals Decision-Making, Errors, and Confidence in the Brain

2010 ◽  
Vol 104 (5) ◽  
pp. 2359-2374 ◽  
Author(s):  
Edmund T. Rolls ◽  
Fabian Grabenhorst ◽  
Gustavo Deco
Keyword(s):  
Decision Making ◽  
Neuronal Activity ◽  
Blood Oxygen Level Dependent ◽  
Linear Increase ◽  
Control Area ◽  
Neuronal Responses ◽  
Blood Oxygen Level ◽  
Decision Confidence ◽  
Fmri Study ◽  
Continuous Scale

To provide a fundamental basis for understanding decision-making and decision confidence, we analyze a neuronal spiking attractor-based model of decision-making. The model predicts probabilistic decision-making with larger neuronal responses and larger functional magnetic resonance imaging (fMRI) blood-oxygen-level-dependent (BOLD) responses on correct than on error trials because the spiking noise-influenced decision attractor state of the network is consistent with the external evidence. Moreover, the model predicts that the neuronal activity and the BOLD response will become larger on correct trials as the discriminability Δ I increases and confidence increases and will become smaller as confidence decreases on error trials as Δ I increases. Confidence is thus an emergent property of the model. In an fMRI study of an olfactory decision-making task, we confirm these predictions for cortical areas including medial prefrontal cortex and the cingulate cortex implicated in choice decision-making, showing a linear increase in the BOLD signal with Δ I on correct trials, and a linear decrease on error trials. These effects were not found in a control area, the orbitofrontal cortex, where reward value useful for the choice is represented on a continuous scale but that is not implicated in the choice itself. This provides a unifying approach to decision-making and decision confidence and to how spiking-related noise affects choice, confidence, synaptic and neuronal activity, and fMRI signals.

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