Selective frontal, parietal, and temporal networks in generalized seizures

Blumenfeld, Hal; Westerveld, Michael; Ostroff, Robert; Vanderhill, Susan; Freeman, Jason; Necochea, Alexandro; Uranga, Paula; Tanhehco, Tasha Y.; Smith, Arien J.; Seibyl, John; Stokking, Rik; Studholme, Colin; Spencer, Susan S.; Zubal, I. George

doi:10.1016/s1053-8119(03)00204-0

Cited by 149 publications

(146 citation statements)

References 53 publications

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“…There is increasing evidence that so-called generalized seizures are in fact of focal origin and that even during generalization some networks are involved more intensely that others [9,20,49,62]. Due to the motor involvement during tonic-clonic seizures, however, imaging studies of the specific networks involved cannot be performed in human patients using fMRI or PET imaging.…”

Section: Default Mode Network Involvement In Generalized Tonic-clonicmentioning

confidence: 99%

“…However, ictal single photon emission computed tomography (SPECT) works by injection of radiopharmaceutical during the seizure; and imaging at a later time can provide a window into changes in cerebral blood flow during seizures, a known marker of neuronal activity. Additionally, intracranial electroencephalography (EEG) [62] and electroconvulsive therapy (ECT) studies have proven useful for understanding these events [7,9,21].…”

Section: Default Mode Network Involvement In Generalized Tonic-clonicmentioning

confidence: 99%

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The Default Mode Network and Altered Consciousness in Epilepsy

Danielson

Guo

Blumenfeld

2011

Behavioural Neurology

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139

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Abstract. The default mode network has been hypothesized based on the observation that specific regions of the brain are consistently activated during the resting state and deactivated during engagement with task. The primary nodes of this network, which typically include the precuneus/posterior cingulate, the medial frontal and lateral parietal cortices, are thought to be involved in introspective and social cognitive functions. Interestingly, this same network has been shown to be selectively impaired during epileptic seizures associated with loss of consciousness. Using a wide range of neuroimaging and electrophysiological modalities, decreased activity in the default mode network has been confirmed during complex partial, generalized tonic-clonic, and absence seizures. In this review we will discuss these three seizure types and will focus on possible mechanisms by which decreased default mode network activity occurs. Although the specific mechanisms of onset and propagation differ considerably across these seizure types, we propose that the resulting loss of consciousness in all three types of seizures is due to active inhibition of subcortical arousal systems that normally maintain default mode network activity in the awake state. Further, we suggest that these findings support a general "network inhibition hypothesis," by which active inhibition of arousal systems by seizures in certain cortical regions leads to cortical deactivation in other cortical areas. This may represent a push-pull mechanism similar to that seen operating between cortical networks under normal conditions.

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Section: Default Mode Network Involvement In Generalized Tonic-clonicmentioning

confidence: 99%

Section: Default Mode Network Involvement In Generalized Tonic-clonicmentioning

confidence: 99%

The Default Mode Network and Altered Consciousness in Epilepsy

Danielson

Guo

Blumenfeld

2011

Behavioural Neurology

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139

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“…During the ictal period of ECT, there is an increase in CBF (McNally and Blumenfeld 2004), with the increase being largest where stimulation has been provided (Blumenfeld et al 2003), followed by a postictal or interictal decrease (Prohovnik et al 1986, Segawa et al 2006. This decrease then tends to recover gradually after the course of ECT has been completed (Navarro et al 2002, Takano et al 2006).…”

Section: Significant Shifts In Perfusion Ratios After Ectmentioning

confidence: 99%

On electroconvulsive therapy in depression : Clinical, cognitive and neurobiological aspects

Nordanskog¹

2015

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Electroconvulsive therapy (ECT) is used worldwide to treat severe mental disorders. The most common mental disorder, and the third leading cause of disease burden in the world is depression. The clinical efficacy of ECT for severe depression is well-established. However, both the pathophysiology of depression and the mechanism of action of ECT remain elusive. The main aims of this thesis are to address the following issues: 1) the use and practice of ECT in Sweden has not been systematically evaluated since 1975, 2) cognitive side-effects (memory disturbances) are a major concern with ECT and 3) the mechanism of action of ECT remain elusive. The neurobiological aspects of ECT focus on two hypotheses. First, the recent years´ preclinical studies that have provided evidence that ECT induces hippocampal cell proliferation, including neurogenesis. Second, that enhanced functional inhibition of neuronal activity is a key feature. Current use and practice of ECT in Sweden (paper I) is based on data from the national quality register for ECT, the mandatory patient register of the National Board of Health and Welfare and a survey. Treated person rate (TPR) in Sweden 2013 was found to be 41 individuals / 100 000, and thus unchanged since the latest systematic investigation in Sweden 1975. In more than 70% of treatment series the indication was a depressive episode. The selection of patients for ECT and treatment technique in Sweden was similar to that in other western countries, but the consent procedure and the involvement of nurses and nursing assistants in the delivery of ECT differ. Data also shows that there is room for improvement in both the specificity of use and availability of ECT. The second study in this thesis is a longitudinal observational trial where 12 (paper II and III) and 14 (paper IV) patients with depression referred for ECT were investigated. Patients underwent a 3 T MRI structural scanning and DSC-MRI perfusion, a neuropsychological test battery and clinical ratings before ECT, within one to two weeks after ECT and after 6 and 12 months. In line with preclinical findings and the plasticity hypothesis of mechanism of action of ECT, the hippocampal volume increased after ECT in patients with depression. However, this increase was transient and returned to baseline levels within 6 months. No correlation was found between volumetric changes and clinical effect or cognitive outcome. Instead our results suggested an association to the number of treatments, without relation to the side of stimulation. A right-sided decrease in frontal blood flow distinguished remission from non-remission after ECT. There were significant impairments in verbal episodic memory and verbal fluency within one week after ending the ECT course, but these impairments were transient and no persistent cognitive impairments were seen during the follow-up. In summary, this thesis present the first update on the use and practice of ECT in Sweden in the last 40 years as well as a pioneering MRI-study on the hippocampal volume increase...

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“…3 These network interactions were recently suggested in a study using SPECT data and SPM. 5 Simple partial seizures were associated with more limited changes confined mainly to the temporal lobes. Complex partial seizures were associated with marked rCBF decrease in regions of association cortex, including the lateral prefrontal, anterior cingulate, orbital frontal, and lateral parietal cortex.…”

Section: Single Photon Emission Tomography (Spect)mentioning

confidence: 99%

“…Complex partial seizures were associated with marked rCBF decrease in regions of association cortex, including the lateral prefrontal, anterior cingulate, orbital frontal, and lateral parietal cortex. There is preliminary evidence indicating that abnormal increased activity in fronto-parietal association cortex may cause loss of consciousness in generalized seizures, 5 while abnormal decreased activity in these same networks may cause loss of consciousness in complex partial seizures. 4 A similar result has been previously suggested in an animal model.…”

Section: Single Photon Emission Tomography (Spect)mentioning

confidence: 99%

Neurovascular coupling and functional neuroimaging in epilepsy

Junior

Wichert‐Ana

Silva

et al. 2009

J. epilepsy clin. neurophysiol.

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Introduction:The neural regulation of the microcirculation is done by the functional neurovascular unit that is composed of vascular, astroglial and neuronal cells. The neurovascular unit represents the interface between the Central Nervous System and the Vascular System. Objective: This paper reviews the literature on functional neuroimaging with a particular focus on the mechanisms of the neurovascular coupling. Conclusions: Functional neuroimaging techniques as functional MRI, SPECT and PET distinguish metabolic and physiological processes underlying normal and abnormal events, based on neurovascular coupling. Although these techniques still have limitations in temporal and spatial resolution, they have considerably reduced the need for intracranial electrodes or invasive functional tests in the presurgical evaluation for intractable epilepsy. Recently, new techniques as optical approaches (measurement of intrinsic optical signals and near infrared spectroscopy) have increased both temporal and spatial resolutions. The use of such techniques in animal models has yielded experimental evidence for a neurovascular coupling in normal and epileptic conditions.

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Selective frontal, parietal, and temporal networks in generalized seizures

Cited by 149 publications

References 53 publications

The Default Mode Network and Altered Consciousness in Epilepsy

The Default Mode Network and Altered Consciousness in Epilepsy

On electroconvulsive therapy in depression : Clinical, cognitive and neurobiological aspects

Neurovascular coupling and functional neuroimaging in epilepsy

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