Elhum Shamshiri

Elhum Shamshiri
San Francisco VA Medical Center | VAMC · Brain Imaging and EEG Laboratory

PhD

About

15
Publications
1,251
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189
Citations

Publications

Publications (15)
Preprint
Full-text available
Background Schizophrenia is associated with aberrant gamma band power, hypothesized to reflect imbalance in the excitation-inhibition (E/I) ratio and undermine neural signal efficiency. Relationships between resting-state gamma, E/I balance, and regional hemodynamics from the fMRI BOLD signal are unknown. Methods We recorded simultaneous EEG-fMRI...
Article
Full-text available
OBJECTIVE: Whilst stimulation of the anterior nucleus of the thalamus has shown efficacy for reducing seizure frequency in adults, alterations in thalamic connectivity have not been explored in children. We tested the hypotheses that (a) the anterior thalamus has increased functional connectivity in children with focal epilepsy, and (b) this altera...
Article
Full-text available
Both electroencephalography (EEG) and functional Magnetic Resonance Imaging (fMRI) are non-invasive methods that show complementary aspects of human brain activity. Despite measuring different proxies of brain activity, both the measured blood-oxygenation (fMRI) and neurophysiological recordings (EEG) are indirectly coupled. The electrophysiologica...
Preprint
Both electroencephalography (EEG) and functional Magnetic Resonance Imaging (fMRI) are non-invasive methods that show complementary aspects of human brain activity. Despite their differences in probing brain activity, both electrophysiology and BOLD signal can map the underlying functional connectivity structure at the whole brain scale at differen...
Article
Full-text available
Brain functions do not arise from isolated brain regions, but from interactions in widespread networks necessary for both normal and pathological conditions. These Intrinsic Connectivity Networks (ICNs) support cognitive processes such as language, memory, or executive functions, but can be disrupted by epileptic activity. Simultaneous EEG-fMRI can...
Article
Full-text available
Bildgebung und Elektrophysiologieforschung haben gezeigt, dass epileptische Aktivität abnormale Funktionen eines Netzwerks zwischen kortikalen und subkortikalen Strukturen reflektiert. Die Darstellung von Connectivity und die Analyse der zugrunde liegenden Netzwerke (sog. „connectomics, graph analysis“) sind ein schnell wachsendes Feld der klinisch...
Article
Full-text available
Objective: Patients with genetic generalized epilepsy (GGE) have subtle morphologic abnormalities of the brain revealed with magnetic resonance imaging (MRI), particularly in the thalamus. However, it is unclear whether morphologic abnormalities of the brain in GGE are a consequence of repeated seizures over the duration of the disease, or are a c...
Article
Full-text available
Objective: Surgical treatment in epilepsy is effective if the epileptogenic zone (EZ) can be correctly localized and characterized. Here we use simultaneous electroencephalography-functional magnetic resonance imaging (EEG-fMRI) data to derive EEG-fMRI and electrical source imaging (ESI) maps. Their yield and their individual and combined ability...
Conference Paper
The interrelationship between cerebral haemodynamics and epileptic activity has been the subject of study for over 100 years. The overall goal of this PhD is to use and develop multimodal imaging to better understand this relationship in a paediatric population. This has important implications for the localisation of epileptic activity that can aid...
Article
Patients with focal epilepsy have been shown to have reduced functional connectivity in intrinsic connectivity networks (ICNs), which has been related to neurocognitive development and outcome. However, the relationship between interictal epileptiform discharges (IEDs) and changes in ICNs remains unclear, with evidence both for and against their in...
Article
Full-text available
Background: Early surgical intervention in children with drug resistant epilepsy has benefits but requires using tolerable and minimally invasive tests. EEG-fMRI studies have demonstrated good sensitivity for the localization of epileptic focus but a poor yield although the reasons for this have not been systematically addressed. While adults EEG-...
Article
Different noise sources in fMRI acquisition can lead to spurious false positives and reduced sensitivity. We have developed a biophysically-based model (named FIACH: Functional Image Artefact Correction Heuristic) which extends current retrospective noise control methods in fMRI. FIACH can be applied to both General Linear Model (GLM) and resting s...
Conference Paper
Background / Purpose: This ongoing project asks the question: “Do visual numerosity judgments depend only on the perceptual strength of the difference between targets versus distractors?”If so, then the visual property that makes targets different from distractors should not matter. Specifically, if the perceptual strength of the difference betwe...

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