Biomedical subjects

Elizabeth W Pang

Publications and source records attributed to Elizabeth W Pang.

7 recordsLinked to original sources

PubMed2007

Task-related modulation of early cortical responses during language production: an event-related synthetic aperture magnetometry study.

We used whole-head magnetoencephalography measurements to investigate the spatiotemporal pattern of neural activity related to language production. Eight participants overtly responded by repeating aloud or vocalizing an internally generated verb to auditorily or visually presented nouns. Activity peaked within primary sensory (auditory or visual) cortices between 75 and 130 ms after stimulus onset, association cortices (inferior and superior temporal gyri) between 130 and 170 ms, and inferior frontal and premotor areas between 150 and 240 ms. Common to auditory and visual modalities, peak activity at about 220 ms was significantly larger in bilateral inferior frontal and left precentral regions when participants generated a verb than when they repeated a noun. These early differences in frontal regions may reflect the allocation of resources to the processing of low-level perceptions that are projected to the premotor areas early in the preparation of language production.

Adult↗

PubMed2006

Pediatric magnetoencephalography and magnetic source imaging.

Magnetoencephalography (MEG) and magnetic source imaging (MSI) together represent a uniquely powerful functional imaging modality because of their capabilities of directly observing the electrophysiologic activity of neurons with exquisite temporal detail and accurately localizing corresponding neuromagnetic field sources onto high-resolution MR images. These features have and should continue to advance our understanding of the complex spatiotemporal basis of normal and abnormal brain function and development in children. By more clearly delineating and characterizing epileptogenic foci and their relation to eloquent cortex, MSI enables earlier and more effective neurosurgery to be performed, thus resulting in improved seizure outcomes. Although MEG and MSI cannot replace scalp electroencephalography, neuropsychologic testing, and the need for meticulous intraoperative cortical mapping in patients undergoing excision of epileptogenic lesions, their increasing availability should ultimately persuade many clinicians of their key, if not essential, role in the evaluation and treatment of children with epilepsy.

Brain Diseases↗

PubMed2006

Word and face recognition in children with congenital hypothyroidism: an event-related potential study.

The repetition paradigm offers a useful technique for assessing recognition memory by evaluating how an individual responds to new versus old stimuli. While this paradigm has been extensively used in adults with and without clinical conditions, it has not, to our knowledge, been studied in a clinical pediatric population. Children with congenital hypothyroidism (CH) identified by newborn screening and treated early in life have normal intelligence but demonstrate residual cognitive deficits including selective memory problems that are attributed to their loss of thyroid hormone during hippocampal formation. Since the hippocampus is integral for recognition memory, we hypothesized that children with CH would perform atypically on the repetition paradigm. Event-related potentials (ERPs) were recorded during word and face recognition in nine children aged 11 to 13 years with CH and nine typically developing children matched for age. Results revealed that while the groups did not differ in accuracy or reaction time, they did differ significantly on selective ERP components. Like normal adults, the comparison children showed a positive elevation in P3 amplitude for repeated relative to new words at the parietal electrodes, whereas children with CH did not. Both groups produced weak repetition effects when viewing faces, although the amplitudes of children with CH were somewhat smaller. It is proposed that the dampened neurophysiological response to repeated verbal stimuli by children with CH may explain some of their clinically observed difficulties in short-term recognition memory.

Adolescent↗

PubMed2004

Cortical auditory evoked potentials in autism: a review.

The question of etiology in autism remains elusive primarily due to the fact that autism does not result from a single dysfunction but is multi-faceted in nature. Investigations into etiology have ranged from identifying abnormalities in the genome to describing structural/functional brain abnormalities. Bearing in mind the risk of over-simplification, there is still utility in isolating a specific deficit to examine its etiologic contribution. It is known that individuals with autism have difficulty processing auditory information at the cortical level but this is not consistently seen subcortically. In recent years, cortical auditory processing has been extensively researched using event-related potentials (ERPs); however, these results in relation to autism have not been reviewed. This paper will examine this literature and discuss implications for future research.

Autistic Disorder↗

PubMed2003

Localization of auditory N1 in children using MEG: source modeling issues.

Techniques for localizing auditory (AEF) sources are a topic of on-going discussion and this is particularly pertinent in pediatric research. Smaller head sizes are: (1) subject to bilateral temporal lobe source interference from both temporal lobes; and (2) further from MEG sensors resulting in poorer signal-to-noise ratios. An additional consideration in children is that the components of the AEF have distinct contributions along the development spectrum resulting in an ever-changing morphology for the pediatric AEF. These factors present a complicated picture for dipole fitting and raise the question of the most effective fitting strategy. We examined the AEF localizations in five children from 151, 70 and 47 MEG channels of data. We found evidence that bilateral source interaction could result in localization errors along the medial-lateral axis of up to 1 cm. We suggest that any modeling strategy needs to sufficiently account for this interaction and more precise models allowing for multiple sources need to be developed.

Acoustic Stimulation↗

PubMed2003

The significance of ear plugging in localization-related epilepsy.

PURPOSE: The localizing value of ear plugging in the treatment of auditory onset partial seizures, to our knowledge, has not been previously described. We propose that ear plugging is a clinical response to a sensory seizure manifested as an auditory hallucination and a tool for identifying the seizure focus in the auditory cortex on the superior temporal gyrus. METHODS: We report on three children who had prior epilepsy surgery for recurrent symptomatic localization-related epilepsy and who, subsequent to their surgery, displayed stereotyped unilateral or bilateral ear plugging at the onset of partial seizures. We studied scalp video electroencephalography (VEEG), magnetoencephalography (MEG), and magnetic resonance imaging (MRI) in all three. Additionally, we used electrocorticography (ECoG) in two patients, intracranial VEEG monitoring in one patient, and functional MRI language mapping in two patients. RESULTS: All three patients plugged their ears with their hands during auditory auras that localized to the superior temporal gyrus and were followed by partial seizures that spread to a wider field, as shown on scalp and intracranial VEEG. All three patients had MEG interictal discharges in the superior temporal gyrus. One patient who was nonverbal and unable to describe an auditory phenomenon plugged the ear contralateral to where temporal lobe-onset seizures and MEG interictal discharges occurred. CONCLUSIONS; Ear-plugging seizures indicate an auditory aura and may also lateralize seizure onset to the contralateral temporal lobe auditory cortex. Stereotyped behaviors accompanied by epileptic seizures in children who have poor communication skills are important in the seizure semiology of localization-related epilepsy.

Adolescent↗

PubMed2002

Complex central cortex in pediatric patients with malformations of cortical development.

We investigated whether malformations of cortical development yield a complex central cortex by studying nine children with malformations of cortical development and seven without malformations who underwent epilepsy surgery following extraoperative subdural somatosensory evoked potential and electrical stimulation to identify the sensorimotor cortex. We analyzed superficial structures of the central cortex, latency, amplitude, and location of N20 and P25. Sensorimotor responses in malformations of cortical development extended across the central sulcus in 1 to 4 of 3 to 12 electrodes (mean 32%) compared with 1 to 6 of 4 to 15 electrodes (mean 12%) in cases without malformations with a statistical significance (P < .05). N20 amplitudes were lower in epileptic than nonepileptic cortices (three with and three without malformations of cortical development) (P < .05). The central vein coursed partially along the central sulcus in eight cases of malformations of cortical development and five cases without malformations. We conclude that the sensorimotor cortex in malformations of cortical development is more complex than in cases without malformations, reduced N20 amplitude is indicative of epileptic sensorimotor cortex, and superficial veins do not indicate the sensory and motor cortical boundary.

Adolescent↗