scholarly journals Low Frequency Stimulation of the Perforant Pathway Generates Anesthesia-Specific Variations in Neural Activity and BOLD Responses in the Rat Dentate Gyrus

2011 ◽  
Vol 32 (2) ◽  
pp. 291-305 ◽  
Author(s):  
Karla Krautwald ◽  
Frank Angenstein
Keyword(s):  
Dentate Gyrus ◽  
Stimulus Frequency ◽  
Low Frequency ◽  
Blood Oxygen Level Dependent ◽  
Bold Response ◽  
Blood Oxygen Level ◽  
Perforant Pathway ◽  
Bold Responses ◽  
Dependent Signal ◽  
Frequency Stimulation

To study how various anesthetics affect the relationship between stimulus frequency and generated functional magnetic resonance imaging (fMRI) signals in the rat dentate gyrus, the perforant pathway was electrically stimulated with repetitive low frequency (i.e., 0.625, 1.25, 2.5, 5, and 10 Hz) stimulation trains under isoflurane/N2O, isoflurane, medetomidine, and α-chloralose. During stimulation, the blood oxygen level-dependent signal intensity (BOLD response) and local field potentials in the dentate gyrus were simultaneously recorded to prove whether the present anesthetic controls the generation of a BOLD response via targeting general hemodynamic parameters, by affecting mechanisms of neurovascular coupling, or by disrupting local signal processing. Using this combined electrophysiological/fMRI approach, we found that the threshold frequency (i.e., the minimal frequency required to trigger significant BOLD responses), the optimal frequency (i.e., the frequency that elicit the strongest BOLD response), and the spatial distribution of generated BOLD responses are specific for each anesthetic used. Concurrent with anesthetic-dependent characteristics of the BOLD response, we found the pattern of stimulus-induced neuronal activity in the dentate gyrus is also specific for each anesthetic. Consequently, the anesthetic-specific influence on local signaling processes is the underlying cause for the observation that an identical stimulus elicits different BOLD responses under various anesthetics.

Identification of Cerebral Networks by Classification of the Shape of BOLD Responses

2003 ◽  
Vol 90 (1) ◽  
pp. 360-371 ◽  
Author(s):  
Giovanni d'Avossa ◽  
Gordon L. Shulman ◽  
Maurizio Corbetta
Keyword(s):  
Formal Analysis ◽  
Blood Oxygen Level Dependent ◽  
Bold Response ◽  
Blood Oxygen Level ◽  
Match To Sample ◽  
Sustained Activity ◽  
Bold Responses ◽  
Transient Activity ◽  
Posterior Parietal ◽  
Time Courses

Changes in regional blood oxygen level dependent (BOLD) signals in response to brief visual stimuli can exhibit a variety of time-courses. To demonstrate the anatomical distribution of BOLD response shapes during a match to sample task, a formal analysis of their time-courses is presented. An event-related design was used to estimate regional BOLD responses evoked by a cue word, which instructed the subject to attend to the motion or color of an upcoming target, and those evoked by a briefly presented moving target consisting of colored dots. Regional BOLD time-courses were adequately represented by the linear combination of three orthogonal waveforms. BOLD response shapes were then classified using a fuzzy clustering scheme. Three classes (sustained, phasic, and negative) best characterized cue responses. Four classes (sustained, sustained-phasic, phasic, and bi-phasic) best characterized target responses. In certain regions, the shape of the BOLD responses was modulated by the instruction to attend to the target's motion or color. A left frontal and a posterior parietal region showed sustained activity when motion was cued and transient activity when color was cued. A right thalamic and a left lateral occipital region showed sustained activity when color was cued and transient activity when motion was cued. Following the target several regions showed more sustained activity during motion than color trials. In summary, the effect of the task variable was focal following the cue and widespread following the target. We conclude that the temporal patterns of neural activity affected the shape of the BOLD signal.

scholarly journals BOLD Responses in Human Auditory Cortex Are More Closely Related to Transient MEG Responses Than to Sustained Ones

2010 ◽  
Vol 103 (4) ◽  
pp. 2015-2026 ◽  
Author(s):  
Alexander Gutschalk ◽  
Matti S. Hämäläinen ◽  
Jennifer R. Melcher
Keyword(s):  
Auditory Cortex ◽  
Blood Oxygen Level Dependent ◽  
Bold Response ◽  
Blood Oxygen Level ◽  
Bold Fmri ◽  
Duty Cycles ◽  
Wide Range ◽  
Bold Responses ◽  
Tightly Coupled ◽  
Click Train

Blood oxygen level dependent–functional magnetic resonance imaging (BOLD–fMRI) and magnetoencephalographic (MEG) signals are both coupled to postsynaptic potentials, although their relationship is incompletely understood. Here, the wide range of BOLD–fMRI and MEG responses produced by auditory cortex was exploited to better understand the BOLD–fMRI/MEG relationship. Measurements of BOLD and MEG responses were made in the same subjects using the same stimuli for both modalities. The stimuli, 24-s sequences of click trains, had duty cycles of 2.5, 25, 72, and 100%. For the 2.5% sequence, the BOLD response was elevated throughout the sequence, whereas for 100%, it peaked after sequence onset and offset and showed a diminished elevation in between. On the finer timescale of MEG, responses at 2.5% consisted of a complex of transients, including N1m, to each click train of the sequence, whereas for 100% the only transients occurred at sequence onset and offset between which there was a sustained elevation in the MEG signal (a sustained field). A model that separately estimated the contributions of transient and sustained MEG signals to the BOLD response best fit BOLD measurements when the transient contribution was weighted 8- to 10-fold more than the sustained one. The findings suggest that BOLD responses in the auditory cortex are tightly coupled to the neural activity underlying transient, not sustained, MEG signals.

scholarly journals Mapping cognitive and emotional networks in neurosurgical patients using resting-state functional magnetic resonance imaging

2020 ◽  
Vol 48 (2) ◽  
pp. E9 ◽  
Author(s):  
Michael P. Catalino ◽  
Shun Yao ◽  
Deborah L. Green ◽  
Edward R. Laws ◽  
Alexandra J. Golby ◽  
...  
Keyword(s):  
Resting State ◽  
Imaging Modality ◽  
Low Frequency ◽  
Blood Oxygen Level Dependent ◽  
Blood Oxygen Level ◽  
Brain Functions ◽  
Neurosurgical Patients ◽  
Potential Applications ◽  
Dependent Signal ◽  
Intraoperative Electrical Stimulation

Neurosurgery has been at the forefront of a paradigm shift from a localizationist perspective to a network-based approach to brain mapping. Over the last 2 decades, we have seen dramatic improvements in the way we can image the human brain and noninvasively estimate the location of critical functional networks. In certain patients with brain tumors and epilepsy, intraoperative electrical stimulation has revealed direct links between these networks and their function. The focus of these techniques has rightfully been identification and preservation of so-called “eloquent” brain functions (i.e., motor and language), but there is building momentum for more extensive mapping of cognitive and emotional networks. In addition, there is growing interest in mapping these functions in patients with a broad range of neurosurgical diseases. Resting-state functional MRI (rs-fMRI) is a noninvasive imaging modality that is able to measure spontaneous low-frequency blood oxygen level–dependent signal fluctuations at rest to infer neuronal activity. Rs-fMRI may be able to map cognitive and emotional networks for individual patients. In this review, the authors give an overview of the rs-fMRI technique and associated cognitive and emotional resting-state networks, discuss the potential applications of rs-fMRI, and propose future directions for the mapping of cognition and emotion in neurosurgical patients.

scholarly journals NMDA-Dependent Mechanisms Only Affect the BOLD Response in the Rat Dentate Gyrus by Modifying Local Signal Processing

2011 ◽  
Vol 32 (3) ◽  
pp. 570-584 ◽  
Author(s):  
Regina Tiede ◽  
Karla Krautwald ◽  
Anja Fincke ◽  
Frank Angenstein
Keyword(s):  
Signal Processing ◽  
Nmda Receptor ◽  
Dentate Gyrus ◽  
Entorhinal Cortex ◽  
Bold Response ◽  
Electrophysiological Response ◽  
Perforant Pathway ◽  
Bold Responses ◽  
The Right ◽  
Stimulation Of

The role of N-methyl-d-aspartate (NMDA) receptor-mediated mechanisms in the formation of a blood oxygen level-dependent (BOLD) response was studied using electrical stimulation of the right perforant pathway. Stimulation of this fiber bundle triggered BOLD responses in the right hippocampal formation and in the left entorhinal cortex. The perforant pathway projects to and activates the dentate gyrus monosynaptically, activation in the contralateral entorhinal cortex is multisynaptic and requires forwarding and processing of signals. Application of the NMDA receptor antagonist MK801 during stimulation had no effect on BOLD responses in the right dentate gyrus, but reduced the BOLD responses in the left entorhinal cortex. In contrast, application of MK801 before the first stimulation train reduced the BOLD response in both regions. Electrophysiological recordings revealed that the initial stimulation trains changed the local processing of the incoming signals in the dentate gyrus. This altered electrophysiological response was not further changed by a subsequent application of MK801, which is in agreement with an unchanged BOLD response. When MK801 was present during the first stimulation train, a dissimilar electrophysiological response pattern was observed and corresponds to an altered BOLD response, indicating that NMDA-dependent mechanisms indirectly affect the BOLD response, mainly via modifying local signal processing and subsequent propagation.

scholarly journals Association Between Brain Activation and Functional Connectivity

2018 ◽  
Vol 29 (5) ◽  
pp. 1984-1996 ◽  
Author(s):  
Dardo Tomasi ◽  
Nora D Volkow
Keyword(s):  
Functional Connectivity ◽  
Brain Activity ◽  
Low Frequency ◽  
Brain Activation ◽  
Blood Oxygen Level Dependent ◽  
Common Source ◽  
Functional Connectivity Density ◽  
Density Mapping ◽  
Human Connectome Project ◽  
Bold Responses

Abstract The origin of the “resting-state” brain activity recorded with functional magnetic resonance imaging (fMRI) is still uncertain. Here we provide evidence for the neurovascular origins of the amplitude of the low-frequency fluctuations (ALFF) and the local functional connectivity density (lFCD) by comparing them with task-induced blood-oxygen level dependent (BOLD) responses, which are considered a proxy for neuronal activation. Using fMRI data for 2 different tasks (Relational and Social) collected by the Human Connectome Project in 426 healthy adults, we show that ALFF and lFCD have linear associations with the BOLD response. This association was significantly attenuated by a novel task signal regression (TSR) procedure, indicating that task performance enhances lFCD and ALFF in activated regions. We also show that lFCD predicts BOLD activation patterns, as was recently shown for other functional connectivity metrics, which corroborates that resting functional connectivity architecture impacts brain activation responses. Thus, our findings indicate a common source for BOLD responses, ALFF and lFCD, which is consistent with the neurovascular origin of local hemodynamic synchrony presumably reflecting coordinated fluctuations in neuronal activity. This study also supports the development of task-evoked functional connectivity density mapping.

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.

Motor network recovery in patients with chronic spinal cord compression: a longitudinal study following decompression surgery

2018 ◽  
Vol 28 (4) ◽  
pp. 379-388 ◽  
Author(s):  
Kayla Ryan ◽  
Sandy Goncalves ◽  
Robert Bartha ◽  
Neil Duggal
Keyword(s):  
Spinal Cord ◽  
Spinal Cord Compression ◽  
Surgical Intervention ◽  
Blood Oxygen Level Dependent ◽  
Cord Compression ◽  
Decompression Surgery ◽  
Blood Oxygen Level ◽  
Motor Network ◽  
Dependent Signal

OBJECTIVEThe authors used functional MRI to assess cortical reorganization of the motor network after chronic spinal cord compression and to characterize the plasticity that occurs following surgical intervention.METHODSA 3-T MRI scanner was used to acquire functional images of the brain in 22 patients with reversible cervical spinal cord compression and 10 control subjects. Controls performed a finger-tapping task on 3 different occasions (baseline, 6-week follow-up, and 6-month follow-up), whereas patients performed the identical task before surgery and again 6 weeks and 6 months after spinal decompression surgery.RESULTSAfter surgical intervention, an increased percentage blood oxygen level–dependent signal and volume of activation was observed within the contralateral and ipsilateral motor network. The volume of activation of the contralateral primary motor cortex was associated with functional measures both at baseline (r = 0.55, p < 0.01) and 6 months after surgery (r = 0.55, p < 0.01). The percentage blood oxygen level–dependent signal of the ipsilateral supplementary motor area 6 months after surgery was associated with increased function 6 months after surgery (r = 0.48, p < 0.01).CONCLUSIONSPlasticity of the contralateral and ipsilateral motor network plays complementary roles in maintaining neurological function in patients with spinal cord compression and may be critical in the recovery phase following surgery.

scholarly journals Aberrant blood-oxygen-level-dependent signal oscillations across frequency bands characterize the alcoholic brain

2017 ◽  
Vol 23 (2) ◽  
pp. 824-835 ◽  
Author(s):  
Jui-Yang Hong ◽  
Eva M. Müller-Oehring ◽  
Adolf Pfefferbaum ◽  
Edith V. Sullivan ◽  
Dongjin Kwon ◽  
...  
Keyword(s):  
Blood Oxygen Level Dependent ◽  
Blood Oxygen ◽  
Oxygen Level ◽  
Blood Oxygen Level ◽  
Frequency Bands ◽  
Dependent Signal
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