29
views
0
recommends
+1 Recommend
0 collections
    0
    shares
      • Record: found
      • Abstract: found
      • Article: found
      Is Open Access

      An EEG–MEG Dissociation between Online Syntactic Comprehension and Post Hoc Reanalysis

      research-article

      Read this article at

      Bookmark
          There is no author summary for this article yet. Authors can add summaries to their articles on ScienceOpen to make them more accessible to a non-specialist audience.

          Abstract

          Successful comprehension of syntactically complex sentences depends on online language comprehension mechanisms as well as reanalysis in working memory. To differentiate the neural substrates of these processes, we recorded electroencephalography and magnetoencephalography (MEG) during sentence-picture-matching in healthy subjects, assessing the effects of two difficulty factors: syntactic complexity (object-embedded vs. subject-embedded relative clauses) and semantic reversibility on neuronal oscillations during sentence presentation, and during a subsequent memory delay prior to picture onset. Synthetic Aperture magnetometry analysis of MEG showed that semantic reversibility induced left lateralized perisylvian power decreases in a broad frequency range, approximately 8–30 Hz. This effect followed the relative clause presentation and persisted throughout the remainder of the sentence and the subsequent memory delay period, shifting to a more frontal distribution during the delay. In contrast, syntactic complexity induced enhanced power decreases only during the delay period, in bilateral frontal and anterior temporal regions. These results indicate that detailed syntactic parsing of auditory language input may be augmented in the absence of alternative cues for thematic role assignment, as reflected by selective perisylvian engagement for reversible sentences, compared with irreversible sentences in which world knowledge constrains possible thematic roles. Furthermore, comprehension of complex syntax appears to depend on post hoc reanalysis in working memory implemented by frontal regions in both hemispheres.

          Related collections

          Most cited references34

          • Record: found
          • Abstract: found
          • Article: not found

          Removal of eye activity artifacts from visual event-related potentials in normal and clinical subjects.

          Electrical potentials produced by blinks and eye movements present serious problems for electroencephalographic (EEG) and event-related potential (ERP) data interpretation and analysis, particularly for analysis of data from some clinical populations. Often, all epochs contaminated by large eye artifacts are rejected as unusable, though this may prove unacceptable when blinks and eye movements occur frequently. Frontal channels are often used as reference signals to regress out eye artifacts, but inevitably portions of relevant EEG signals also appearing in EOG channels are thereby eliminated or mixed into other scalp channels. A generally applicable adaptive method for removing artifacts from EEG records based on blind source separation by independent component analysis (ICA) (Neural Computation 7 (1995) 1129; Neural Computation 10(8) (1998) 2103; Neural Computation 11(2) (1999) 606) overcomes these limitations. Results on EEG data collected from 28 normal controls and 22 clinical subjects performing a visual selective attention task show that ICA can be used to effectively detect, separate and remove ocular artifacts from even strongly contaminated EEG recordings. The results compare favorably to those obtained using rejection or regression methods. The ICA method can preserve ERP contributions from all of the recorded trials and all the recorded data channels, even when none of the single trials are artifact-free.
            Bookmark
            • Record: found
            • Abstract: found
            • Article: not found

            Signal processing in magnetoencephalography.

            The subject of this article is detection of brain magnetic fields, or magnetoencephalography (MEG). The brain fields are many orders of magnitude smaller than the environmental magnetic noise and their measurement represent a significant metrological challenge. The only detectors capable of resolving such small fields and at the same time handling the large dynamic range of the environmental noise are superconducting quantum interference devices (or SQUIDs). The SQUIDs are coupled to the brain magnetic fields using combinations of superconducting coils called flux transformers (primary sensors). The environmental noise is attenuated by a combination of shielding, primary sensor geometry, and synthetic methods. One of the most successful synthetic methods for noise elimination is synthetic higher-order gradiometers. How the gradiometers can be synthesized is shown and examples of their noise cancellation effectiveness are given. The MEG signals measured on the scalp surface must be interpreted and converted into information about the distribution of currents within the brain. This task is complicated by the fact that such inversion is nonunique. Additional mathematical simplifications, constraints, or assumptions must be employed to obtain useful source images. Methods for the interpretation of the MEG signals include the popular point current dipole, minimum norm methods, spatial filtering, beamformers, MUSIC, and Bayesian techniques. The use of synthetic aperture magnetometry (a class of beamformers) is illustrated in examples of interictal epileptic spiking and voluntary hand-motor activity. Copyright 2001 Elsevier Science.
              Bookmark
              • Record: found
              • Abstract: found
              • Article: not found

              Event-related dynamics of cortical rhythms: frequency-specific features and functional correlates.

              Oscillations in the alpha and beta band (<35 Hz) display a dynamic behavior and show characteristic spatiotemporal patterns in sensory, motor and cognitive tasks. The event-related desynchronization (ERD) of alpha band and beta rhythms can be seen as a correlate of an activated cortical area with an increased excitability level of neurons. An event-related synchronization (ERS) of frequency components between 10 and 13 Hz may represent a deactivated cortical area or inhibited cortical network, at least under certain circumstances. It is hypothesized, that antagonistic ERD/ERS patterns, called 'focal ERD/surround ERS', may reflect a thalamo-cortical mechanism to enhance focal cortical activation by simultaneous inhibition of other cortical areas. Induced oscillations in the beta band (13-35 Hz, beta ERS) were found in sensorimotor areas after voluntary movement and after somatosensory stimulation. This may be interpreted as a state of 'inhibition' of neural circuitry in the primary motor cortex. Simultaneous activation of the motor cortex by e.g. motor imagery lead to an attenuation of the beta ERS. Moreover, there is evidence that the frequency of the induced beta oscillations represent a 'resonance-like frequency' of underlying cortical networks. However, further research is needed to investigate the functional meaning of bursts of beta oscillations below 35 Hz.
                Bookmark

                Author and article information

                Journal
                Front Hum Neurosci
                Front. Hum. Neurosci.
                Frontiers in Human Neuroscience
                Frontiers Research Foundation
                1662-5161
                04 February 2011
                2011
                : 5
                : 10
                Affiliations
                [1] 1simpleLanguage Section, National Institute on Deafness and Other Communication Disorders, National Institutes of Health Bethesda, MD, USA
                Author notes

                Edited by: Judith M. Ford, Yale University School of Medicine, USA

                Reviewed by: Tatiana Sitnikova, Massachusetts General Hospital, USA; Michael Kiang, McMaster University, Canada

                *Correspondence: Jed A. Meltzer, Language Section, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Building 10, Room 5C-410, Bethesda, MD 20892, USA. e-mail: jed.meltzer@ 123456aya.yale.edu
                Article
                10.3389/fnhum.2011.00010
                3035013
                21331355
                4b20ee2b-ff33-49d6-90c2-6beec265f43b
                Copyright © 2011 Meltzer and Braun.

                This is an open-access article subject to an exclusive license agreement between the authors and Frontiers Media SA, which permits unrestricted use, distribution, and reproduction in any medium, provided the original authors and source are credited.

                History
                : 08 July 2010
                : 11 January 2011
                Page count
                Figures: 5, Tables: 1, Equations: 0, References: 53, Pages: 15, Words: 12222
                Categories
                Neuroscience
                Original Research

                Neurosciences
                broca's area,language,complexity,semantic,reversibility,syntax
                Neurosciences
                broca's area, language, complexity, semantic, reversibility, syntax

                Comments

                Comment on this article