MEG Responses Research Articles

Before the N400: Effects of lexical–semantic violations in visual cortex

There exists an increasing body of research demonstrating that language processing is aided by context-based predictions. Recent findings suggest that the brain generates estimates about the likely physical appearance of upcoming words based on syntactic predictions: words that do not physically look like the expected syntactic category show increased amplitudes in the visual M100 component, the first salient MEG response to visual stimulation. This research asks whether violations of predictions based on lexical–semantic information might similarly generate early visual effects. In a picture–noun matching task, we found early visual effects for words that did not accurately describe the preceding pictures. These results demonstrate that, just like syntactic predictions, lexical–semantic predictions can affect early visual processing around ∼100 ms, suggesting that the M100 response is not exclusively tuned to recognizing visual features relevant to syntactic category analysis. Rather, the brain might generate predictions about upcoming visual input whenever it can. However, visual effects of lexical–semantic violations only occurred when a single lexical item could be predicted. We argue that this may be due to the fact that in natural language processing, there is typically no straightforward mapping between lexical–semantic fields (e.g., flowers) and visual or auditory forms (e.g., tulip, rose, magnolia). For syntactic categories, in contrast, certain form features do reliably correlate with category membership. This difference may, in part, explain why certain syntactic effects typically occur much earlier than lexical–semantic effects.

Effects of visual complexity and sublexical information in the occipitotemporal cortex in the reading of Chinese phonograms: A single-trial analysis with MEG

We employ a linear mixed-effects model to estimate the effects of visual form and the linguistic properties of Chinese characters on M100 and M170 MEG responses from single-trial data of Chinese and English speakers in a Chinese lexical decision task. Cortically constrained minimum-norm estimation is used to compute the activation of M100 and M170 responses in functionally defined regions of interest. Both Chinese and English participants’ M100 responses tend to increase in response to characters with a high numbers of strokes. English participants’ M170 responses show a posterior distribution and only reflect the effect of the visual complexity of characters. On the other hand, the Chinese participants’ left hemisphere M170 is increased when reading characters with high number of strokes, and their right hemisphere M170 is increased when reading characters with small combinability of semantic radicals. Our results suggest that expertise with words and the decomposition of word forms underlies processing in the left and right occipitotemporal regions in the reading of Chinese characters by Chinese speakers.

P33-24 Correlations between the development of cognitive functions and spontaneous MEG responses of healthy 3- to 4-year-old infants

P33-24 Correlations between the development of cognitive functions and spontaneous MEG responses of healthy 3- to 4-year-old infants

MEG responses in the human brain during the selection of visual targets

MEG responses in the human brain during the selection of visual targets

Modulation of otolith MEG responses by change of gravitational force vector

Modulation of otolith MEG responses by change of gravitational force vector

Frequency and phase synchronization in neuromagnetic cortical responses to flickering-color stimuli

In our earlier study dealing with the analysis of neuromagnetic responses (magnetoencephalograms - MEG) to flickering-color stimuli for a group of control human subjects (9 volunteers) and a patient with photosensitive epilepsy (a 12-year old girl), it was shown that Flicker-Noise Spectroscopy (FNS) was able to identify specific differences in the responses of each organism. The high specificity of individual MEG responses manifested itself in the values of FNS parameters for both chaotic and resonant components of the original signal. The present study applies the FNS cross-correlation function to the analysis of correlations between the MEG responses simultaneously measured at spatially separated points of the human cortex processing the red-blue flickering color stimulus. It is shown that the cross-correlations for control (healthy) subjects are characterized by frequency and phase synchronization at different points of the cortex, with the dynamics of neuromagnetic responses being determined by the low-frequency processes that correspond to normal physiological rhythms. But for the patient, the frequency and phase synchronization breaks down, which is associated with the suppression of cortical regulatory functions when the flickering-color stimulus is applied, and higher frequencies start playing the dominating role. This suggests that the disruption of correlations in the MEG responses is the indicator of pathological changes leading to photosensitive epilepsy, which can be used for developing a method of diagnosing the disease based on the analysis with the FNS cross-correlation function.

Auditory illusion explored with MEG

Event Abstract Back to Event Auditory illusion explored with MEG Ken-ichi Ouchi1*, Shinya Kuriki2, Asuka Otsuka3 and Makoto Takahashi1 1 Hokkaido University, Japan 2 Tokyo Denki University, Japan 3 The University of Tokyo, Elekta K.K, Japan Deutsch has shown in her paper (1975) an auditory illusion occurring when dichotic tonal sequences are given to listeners in both ascending and descending forms, in a way that a component of the ascending scale is in one ear, a component of the descending scale is in the other, and vice versa repetitively. Most right handed subjects perceived two streams of “scale illusion” where higher tones in the scale appear exclusively in one ear and other lower tones in the other. Here, we made MEG measurements to examine how the dichotic tones in a scale are represented in the right and left auditory cortices using frequency tagging, in which higher and lower tones were amplitude modulated at distinct frequencies of fH and fL. Steady state MEG responses were separated by FFT into fH and fL components. In some subjects who reported the percept of scale illusion, the amplitudes of fH and fL component of contra- (or ipsi-) and ipsi- (or contra-) lateral responses were altered from the normal relation of contralateral preference. Such increment/decrement of the responses in the auditory cortex to some component-tones in the tonal sequence might be related with the percept of scale illusion.

Effects of adaptation on visual sensitivity and MEG responses to the envelope of AM flicker

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Cortical responses to a new dichotic pitch

Event Abstract Back to Event Cortical responses to a new dichotic pitch Caroline Witton1*, Bruce G. Henning2 and Arjan Hillebrand3 1 Aston University, United Kingdom 2 Institute of Opthalmology, United Kingdom 3 VU University Medical Center, Netherlands Evoked-response beamformer analysis (ER-SAM) was used to explore cortical responses to a rapid interaural phase-modulation of narrow-band noise, which produces a newly-described auditory pitch. Whole-head MEG data were collected while participants listened to 100 exemplars of a 1-second noise stimulus (250-Hz bandwidth, centred on 500 Hz), where the pitch-eliciting modulation (60-Hz dichotic FM) was introduced 500 ms from sound onset. One hundred exemplars of a control stimulus where the same FM was diotic were interleaved with the dichotic stimuli. There was a variable ISI of at least 500 ms. Beamformer weights were computed for a 5 to 25 Hz frequency band over two separate 200-ms time windows centred on the evoked responses of interest; the N1-P2 complex at sound onset; and on the pitch onset response which occurred, for this stimulus, approximately 200 ms after FM-onset. The ER-SAM analysis yielded volumetric maps showing spectral power in the average dataset at the time of the peak in the evoked responses. Evoked-response time series were also reconstructed for the peak voxels of interest. For most participants the source of the pitch-onset-response was in planum temporale, just posterior to that for the peak of the N1-P2 onset response in Heschl's gyrus. The responses to the dichotic FM were significantly stronger than in the control condition, supporting our hypothesis that the pitch is a binaural phenomenon. The source in planum temporale is similar to that observed with fMRI for another binaural pitch, 'Huggins pitch', but differs from previous MEG reports for the source of a monaural temporal pitch. There was a strong hemispheric asymmetry which reflected behavioural observations that the pitch was strongly and consistently lateralised. This study contributes to our understanding of binaural pitch perception and provides evidence that MEG responses to pitch may differ depending on how the pitch is elicited. Conference: Biomag 2010 - 17th International Conference on Biomagnetism , Dubrovnik, Croatia, 28 Mar - 1 Apr, 2010. Presentation Type: Poster Presentation Topic: Sensory Processing and Functional Connectivity Citation: Witton C, Henning BG and Hillebrand A (2010). Cortical responses to a new dichotic pitch. Front. Neurosci. Conference Abstract: Biomag 2010 - 17th International Conference on Biomagnetism . doi: 10.3389/conf.fnins.2010.06.00210 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 30 Mar 2010; Published Online: 30 Mar 2010. * Correspondence: Caroline Witton, Aston University, Birmingham, United Kingdom, c.witton@aston.ac.uk Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Caroline Witton Bruce G Henning Arjan Hillebrand Google Caroline Witton Bruce G Henning Arjan Hillebrand Google Scholar Caroline Witton Bruce G Henning Arjan Hillebrand PubMed Caroline Witton Bruce G Henning Arjan Hillebrand Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Somatosensory responses in normal aging, mild cognitive impairment, and Alzheimer’s disease

As a part of a larger study of normal aging and Alzheimer's disease (AD), which included patients with mild cognitive impairment (MCI), we investigated the response to median nerve stimulation in primary and secondary somatosensory areas. We hypothesized that the somatosensory response would be relatively spared given the reported late involvement of sensory areas in the progression of AD. We applied brief pulses of electric current to left and right median nerves to test the somatosensory response in normal elderly (NE), MCI, and AD. MEG responses were measured and were analyzed with a semi-automated source localization algorithm to characterize source locations and timecourses. We found an overall difference in the amplitude of the response of the primary somatosensory source (SI) based on diagnosis. Across the first three peaks of the SI response, the MCI patients exhibited a larger amplitude response than the NE and AD groups (P < 0.03). Additional relationships between neuropsychological measures and SI amplitude were also determined. There was no significant difference in amplitude for the contralateral secondary somatosensory source across diagnostic category. These results suggest that somatosensory cortex is affected early in the progression of AD and may have some consequence on behavioral and functional measures.

A comparison of MEG and fMRI responses to isoluminant and luminance-modulated contours

A comparison of MEG and fMRI responses to isoluminant and luminance-modulated contours

Perceptual interference exacerbates Voice Onset Time-dependent syllable discrimination and alters performance-related MEG response dynamics in patients with schizophrenia.

Perceptual interference exacerbates Voice Onset Time-dependent syllable discrimination and alters performance-related MEG response dynamics in patients with schizophrenia.

Oscillatory MEG Responses Reflect Plasticity in the Motor Cortices of Stroke Patients Following Therapy

Oscillatory MEG Responses Reflect Plasticity in the Motor Cortices of Stroke Patients Following Therapy

Predicting stimulus‐rate sensitivity of human somatosensory fMRI signals with MEG

With increasing stimulus rate (SR), cortical EEG and MEG responses typically decrease in amplitude whereas BOLD fMRI signals increase. To address this discrepancy, we predicted BOLD responses with squared MEG waveforms using a recently proposed energy-density model. Tactile stimuli were delivered to finger tips at SRs of 1, 4, or 10 Hz in successive 25-s blocks, and brain signals were detected from area 3b of the primary somatosensory cortex of nine healthy adults using a 306-channel whole-scalp neuromagnetometer and a 3-T fMRI magnet. The main MEG deflections decreased in amplitude as a function of SR, whereas the BOLD signals increased from 1- to 4-Hz SR, with no further change at 10 Hz. MEG energy densities, obtained over the whole stimulus train and convolved with different hemodynamic response functions, predicted both the shape and amplitude of the BOLD signals well, and incorporation of nonlinear terms into the model did not offer any further advantage. Thus, squared MEG waveforms obtained over the entire stimulus train provided an appropriate estimate of area 3b neuronal activity associated with the BOLD signal.

Visual perception of social interaction: gender effects on oscillatory gamma MEG response

Visual perception of social interaction: gender effects on oscillatory gamma MEG response

Are phrasal verbs treated by the brain as words or as phrases? Magnetic MMN solves long-standing linguistic puzzle

Event Abstract Back to Event Are phrasal verbs treated by the brain as words or as phrases? Magnetic MMN solves long-standing linguistic puzzle Yury Shtyrov1*, B. Cappelle2 and F. Pulvermüller1 1 INSERM, Ecole Normale Superieure, United Kingdom 2 University of Leuven, Belgium In the science of language, there has been a considerable debate as to whether phrasal verbs (e.g., turn up, break down) are processed as two separate items connected by phrase-structure rules or whether they form a single lexical representation. As linguistic and psycholinguistic studies could not unequivocally distinguish between these views, we tested them empirically using neurophysiological brain imaging. Previous work has shown that phrases elicit a reduced oddball response (MMN) if they respect rules of syntactic or semantic coherence compared with word sequences that violate such rules. In contrast, meaningful words that form a lexical representation show an enhanced MMN compared with items not stored in the lexicon. This makes phrasal verbs a straightforward test case: if they are stored and processed as singular lexical items (=words), real phrasal verbs should elicit an increased response as opposed to their meaningless analogues. If, however, they are parsed similar to phrases, then the larger response should be produced by non-existing (=syntactically incorrect/semantically incongruous) verb-particle combinations. We recorded, in passive oddball paradigm, auditory MEG responses to real and non-existing phrasal verbs (heat up, cool down, *cool up,*heat down, etc). Continuous MEG and HPI data were acquired using Neuromag 306-channel system placed in a light MSR, and processed offline using temporal signal space separation technique. Oddball auditory evoked fields to the same phrase-final particles (up, down) presented in proper and in infelicitous contexts were computed and compared to each other. We found that already at latencies below 200 ms, the brain's response was larger when the same acoustic event was part of a real phrasal verb (fall down, rise up) than when it was included in a non-existing item (rise down, fall up). Using L1 minimum current estimates, we found this enhancement to be bilaterally distributed in the perisylvian cortices and the temporal pole. In conjunction with earlier findings of the lexical enhancement of the MMN response, this increased activation for meaningful phrasal verbs strongly suggests that a verb and its particle together form one single lexical representation, i.e. a single lexeme, and that a unified cortical memory circuit exists for it, similar to that encoding a monomorphemic word. Conference: MMN 09 Fifth Conference on Mismatch Negativity (MMN) and its Clinical and Scientific Applications, Budapest, Hungary, 4 Apr - 7 Apr, 2009. Presentation Type: Poster Presentation Topic: Poster Presentations Citation: Shtyrov Y, Cappelle B and Pulvermüller F (2009). Are phrasal verbs treated by the brain as words or as phrases? Magnetic MMN solves long-standing linguistic puzzle. Conference Abstract: MMN 09 Fifth Conference on Mismatch Negativity (MMN) and its Clinical and Scientific Applications. doi: 10.3389/conf.neuro.09.2009.05.054 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 24 Mar 2009; Published Online: 24 Mar 2009. * Correspondence: Yury Shtyrov, INSERM, Ecole Normale Superieure, Cambridge, United Kingdom, yury.shtyrov@cfin.au.dk Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Yury Shtyrov B. Cappelle F. Pulvermüller Google Yury Shtyrov B. Cappelle F. Pulvermüller Google Scholar Yury Shtyrov B. Cappelle F. Pulvermüller PubMed Yury Shtyrov B. Cappelle F. Pulvermüller Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Forward and backward connections in the brain: A DCM study of functional asymmetries

In this paper, we provide evidence for functional asymmetries in forward and backward connections that define hierarchical architectures in the brain. We exploit the fact that modulatory or nonlinear influences of one neuronal system on another (i.e., effective connectivity) entail coupling between different frequencies. Functional asymmetry in forward and backward connections was addressed by comparing dynamic causal models of MEG responses induced by visual processing of normal and scrambled faces. We compared models with and without nonlinear (between-frequency) coupling in both forward and backward connections. Bayesian model comparison indicated that the best model had nonlinear forward and backward connections. Using the best model we then quantified frequency-specific causal influences mediating observed spectral responses. We found a striking asymmetry between forward and backward connections; in which high (gamma) frequencies in higher cortical areas suppressed low (alpha) frequencies in lower areas. This suppression was significantly greater than the homologous coupling in the forward connections. Furthermore, exactly the asymmetry was observed when we examined face-selective coupling (i.e., coupling under faces minus scrambled faces). These results highlight the importance of nonlinear coupling among brain regions and point to a functional asymmetry between forward and backward connections in the human brain that is consistent with anatomical and physiological evidence from animal studies. This asymmetry is also consistent with functional architectures implied by theories of perceptual inference in the brain, based on hierarchical generative models.

Optic flow in human vision: MEG reveals a foveo-fugal bias in V1, specialization for spiral space in hMSTs, and global motion sensitivity in the IPS

We recorded MEG responses from 17 participants viewing random-dot patterns simulating global optic flow components (expansion, contraction, rotation, deformation, and translation) and a random motion control condition. Theta-band (3-7 Hz), MEG signal power was greater for expansion than the other optic flow components in a region concentrated along the calcarine sulcus, indicating an ecologically valid, foveo-fugal bias for unidirectional motion sensors in V1. When the responses to the optic flow components were combined, a decrease in MEG beta-band (17-23 Hz) power was found in regions extending beyond the calcarine sulcus to the posterior parietal lobe (inferior to IPS), indicating the importance of structured motion in this region. However, only one cortical area, within or near the V5/hMT+ complex, responded to all three spiral-space components (expansion, contraction, and rotation) and showed no selectivity for global translation or deformation: we term this area hMSTs. This is the first demonstration of an exclusive region for spiral space in the human brain and suggests a functional role better suited to preliminary analysis of ego-motion than surface pose, which would involve deformation. We also observed that the rotation condition activated the cerebellum, suggesting its involvement in visually mediated control of postural adjustment.

Stochastic Resonance in Auditory Steady State Responses in MEG Observed as Increase in Their Power and Phase Synchrony

We measured auditory steady state responses (ASSRs) in magnetoencephalogram to the sinusoidal amplitude modulated tone superimposed with ongoing white noise of various intensities. The power and phase coherence of the ASSR were investigated and stochastic resonance (SR) was indicated by increased synchrony to the stimulus and by increase in power of the ASSR when there was a certain amount of noise compared with those measured without the noise. We also measured the hearing threshold for the noise alone and found that the optimum noise intensity for SR was slightly larger than the threshold for most of the subjects. As the power and coherence curves plotted against the noise to signal ratio varied considerably among subjects, we used the maximum values of power and phase coherence as test statistics for testing the group data.

Sensory MEG Responses Predict Successful and Failed Inhibition in a Stop-Signal Task

In the present study magnetoencephalographic recordings were performed to investigate the neural mechanisms underlying the stopping of manual responses. Subjects performed in a Stop-signal task in which Go-stimuli (S1), requiring a rapid motor response, were sometimes rapidly followed by a Stop-stimulus (S2) indicating to withhold the already initiated response to S1. Success of stopping strongly depended on the early perceptual processing of S1 and S2 reflected by the magnetic N1 component. Enhanced processing of S1 facilitated the execution of the movement, whereas enhanced processing of S2 favored its inhibition. This suggests that the processing resources for the subsequent stimuli are limited and need to be shared. This sharing of resources appeared to arise from adjustments made on a trial-by-trial basis, in that systematic reaction time prolongations on Go-trials following Stop-trials versus following Go-trials were accompanied by attenuated sensory processing to the Go-stimulus similar to that seen in successful versus unsuccessful stopping in Stop-trials.