Temporal course of word recognition in skilled readers: a magnetoencephalography study.

The goal of the study was to investigate the neural circuit recruited by adult readers during performance of a lexical decision task by assessing the relative timing of neurophysiological activity in the brain regions that comprise this circuit. The time course of regional activation associated with lexical decision was studied in 17 adult volunteers using magnetoencephalography. Following activity in mesial occipital cortices, activation progressed to lateral and ventral occipito-temporal regions (often encompassing the posterior portion of the middle temporal gyrus), followed by activity in the superior temporal gyri (STGp), motor/premotor cortices, and the inferior frontal gyrus.

Altering the brain circuits for reading through intervention: a magnetic source imaging study.

Intervention-related changes in spatiotemporal profiles of regional brain activation were examined by whole-head magnetoencephalography in 15 children with severe reading difficulties who had failed to show adequate progress to quality reading instruction during Grade 1. Intensive intervention initially focused on phonological decoding skills (for 8 weeks) and, during the subsequent 8 weeks, on rapid word recognition ability. Clinically significant improvement in reading skills was noted in 8 children who showed "normalizing" changes in their spatiotemporal profiles of regional brain activity (increased duration of activity in the left temporoparietal region and a shift in the relative timing of activity in temporoparietal and inferior frontal regions).

Intensive instruction affects brain magnetic activity associated with oral word reading in children with persistent reading disabilities.

Fifteen children ages 7 to 9 years who had persistent reading difficulties despite adequate instruction were provided with intensive tutorial interventions. The interventions targeted deficient phonological processing and decoding skills for 8 weeks (2 hours per day) followed by an 8-week, 1-hour-per-day intervention that focused on the development of reading fluency skills. Spatiotemporal brain activation profiles were obtained at baseline and after each 8-week intervention program using magnetoencephalography during the performance of an oral sight-word reading task.

A comparison of functional MRI and magnetoencephalography for receptive language mapping.

We compared functional magnetic resonance imaging (fMRI) and magnetoencephalography (MEG) for the mapping of receptive language function. Participants performed the same language task in the two different imaging environments. MEG activation profiles showed prominent bilateral activity in superior temporal gyrus and left-lateralized activity in middle temporal gyrus.

Magnetic source imaging studies of dyslexia interventions.

Rapidly accumulating evidence from functional brain imaging studies indicates that developmental reading disability is associated with a functional disruption of the brain circuits that normally develop to support reading-related processes. This article briefly overviews recent advances in methods that capture the anatomical outline and temporal (dynamic) features of regional brain activation during performance of reading tasks. One of these methods, magnetoencephalography (MEG) or magnetic sources imaging (MSI) is described in more detail in the context of investigations of changes in spatiotemporal patterns of brain activity associated with improvement in reading skills in response to various types of educational interventions.

Early development of neurophysiological processes involved in normal reading and reading disability: a magnetic source imaging study.

This longitudinal study examined the development of the brain mechanism involved in phonological decoding in beginning readers using magnetic source imaging. Kindergarten students were assigned to 2 groups: those who showed mastery of skills that are important predictors of proficient reading (low-risk group) and those who initially did not show mastery but later benefited from systematic reading instruction and developed average-range reading skills at the end of Grade 1 (high-risk responders). Spatiotemporal profiles of brain activity were obtained during performance of letter-sound and pseudoword naming tasks before and after Grade 1 instruction.

Reproducibility of measures of neurophysiological activity in Wernicke's area: a magnetic source imaging study.

Objective: The purpose of this study was to evaluate the reproducibility of estimates of neurophysiological activity obtained with Magnetic Source Imaging.

Methods: Split-half data sets were obtained from 14 healthy volunteers during performance of a continuous recognition task for spoken words. The concurrent validity of spatiotemporal activation maps obtained with this task has been previously verified through comparisons with the Wada test and electrocortical stimulation mapping.

Toward the substitution of invasive electroencephalography in epilepsy surgery.

The authors compared the localization accuracy of interictal magnetoencephalography (MEG) with ictal and interictal invasive video electroencephalography (VEEG) in identifying the epileptogenic zone in epilepsy surgery candidates. Forty-one patients, 29 with temporal lobe epilepsy (TLE) and 12 with extratemporal lobe epilepsy (ETLE), participated. Only patients with interictal changes during the MEG recordings were included.

Atypical language representation in patients with chronic seizure disorder and achievement deficits with magnetoencephalography.

Purpose: To characterize the relation between hemispheric asymmetries in language-specific brain activity and reading/spelling achievement by using magnetoencephalography (MEG).

Methods: Patients (n = 83) with medically intractable complex partial seizures of either left- or right-hemisphere origin were classified as having reading and/or spelling deficits (RS) or as not impaired (NI) by using standard achievement tests. All patients had undergone noninvasive functional mapping of receptive language cortex by using MEG as part of a preoperative seizure surgery evaluation.

Magnetocephalography: a noninvasive alternative to the Wada procedure.

Object: In this study the authors evaluated the sensitivity and selectivity of a noninvasive language mapping procedure based on magnetoencephalography (MEG), for determining hemispheric dominance for language functions.

Methods: Magnetic activation profiles of the brain were obtained from 100 surgical candidates (age range 8-56 years) with medically intractable seizure disorder by using a whole-head MEG system within the context of a word recognition task. The degree of language-specific activity was indexed according to the number of consecutive sources (modeled as single, moving current dipoles) in perisylvian brain areas.

Integrating sensory and motor mapping in a comprehensive MEG protocol: clinical validity and replicability.

Considerable evidence supports the idea of magnetoencephalography (MEG) being a valuable noninvasive tool for presurgical mapping of sensory and motor functions. In this study, we test the validity and replicability of a new experimental paradigm for simultaneous sensory and motor mapping using MEG recordings. This comprehensive sensorimotor protocol (CSSMP), where external mechanic stimulation serves as a cue for voluntary movements, allows the recording of sensory and motor cortical responses during a single activation task.

Multimodality neuroimaging evaluation improves the detection of subtle cortical dysplasia in seizure patients.

The purpose of this study is to investigate if multimodality neuroimaging evaluation increases the detection of subtle focal cortical dysplasia as part of an epilepsy surgery evaluation. Three patients with normal magnetic resonance imaging and histopathological findings of focal cortical dysplasia were reviewed. Their magnetoencephalography recordings were performed on whole-head magnetoencephalography system.

Contributions of magnetic source imaging to the understanding of dyslexia.

The problem in dyslexia is difficulty learning how the printed word maps onto spoken language. Magnetic Source Imaging protocols were used in three studies. The first study with dyslexic children showed greater activity in the right temporoparietal region.