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Abstract
Chemosensory event-related potentials (CSERPs) have found their way into a number offields of research where they help to determine the function of both the trigeminal and the olfactory system. The investigation of chemosensory deficits in patients with Parkinson's or Alzheimer's disease is only one of the typical applications. It can be assumed that scientists involved in research on patients with multiple chemical sensitivities will also benefit from having access to objective data covering different aspects of the sense of smell.
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Affiliation(s)
- Gerd Kobal
- Department of Experimental and Clinical Pharmacology and Toxicology University of
Erlangen-Nrnberg Erlangen, Germany
| | - Thomas Hummel
- Department of Experimental and Clinical Pharmacology and Toxicology University of
Erlangen-Nrnberg Erlangen, Germany
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Korpi ER, Lindholm D, Panula P, Tienari PJ, Haltia M. Finnish neuroscience from past to present. Eur J Neurosci 2020; 52:3273-3289. [PMID: 32017266 DOI: 10.1111/ejn.14693] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2020] [Revised: 01/24/2020] [Accepted: 01/28/2020] [Indexed: 11/27/2022]
Affiliation(s)
- Esa R Korpi
- Department of Pharmacology, Faculty of Medicine, University of Helsinki, Helsinki, Finland
| | - Dan Lindholm
- Department of Biochemistry and Developmental Biology, Faculty of Medicine, University of Helsinki, Helsinki, Finland.,Minerva Foundation Institute for Medical Research, Helsinki, Finland
| | - Pertti Panula
- Department of Anatomy, Faculty of Medicine, University of Helsinki, Helsinki, Finland
| | - Pentti J Tienari
- Research Programs Unit, Translational Immunology, University of Helsinki, Helsinki, Finland.,Department of Neurology, Neurocenter, Helsinki University Hospital, Helsinki, Finland
| | - Matti Haltia
- Department of Pathology, Faculty of Medicine, University of Helsinki, Helsinki, Finland
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Broser PJ, Moor V, Braun C. A Non-Magnetic Rotating Disk Stimulator for the Study of Neuromagnetic Correlates of Sensorimotor Interaction. IEEE Trans Neural Syst Rehabil Eng 2015; 23:1078-84. [PMID: 25823039 DOI: 10.1109/tnsre.2015.2414482] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Fine motor skills in humans require close interaction between the motor and the sensory systems. It is still not fully understood, how sensory feedback modulates motor commands. This is due to the fact, that there is no approach for investigating the sensorimotor cortical-interaction in sufficient detail. The fast and precise communication between the sensory and motor-systems requires measurements of cortical activity with high temporal and spatial resolution. Magnetoencephalography (MEG) is capable of both. Previously, we showed that sensory responses, can be observed by repetitive tactile stimulation. Further, motor cortex responses can be generated by periodical increase and decrease of muscle tone. Utilizing both observations we have designed an MEG and magnetic resonance imaging (MRI) compatible stimulator allowing for the study of brain activity related to sensorimotor integration. The stimulator consists of a rotating disk with an elevation such that subject senses with his finger the speed of the disk. With the force applied by the finger onto the disk, the subject can control its speed. During the experiment the subject is asked to keep the speed of the disk constant while the driving torque is systematically manipulated. This closed-loop design is especially useful to analyze the fast and continuous information flow between the two systems. In a single case pilot study using MEG, we could show that a detailed analysis of the sensorimotor-network is possible. In contrast to existing paradigms this setup allows separate time-locked analysis of the sensory- and motor-component independently and therefore the calculation of latency parameters for both systems. In the future this method will help to understand the interaction between the two systems in much greater detail.
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Abstract
The still continuing accelerated development of neurology in Germany is described in this article by a contemporary witness who was active in this field from 1965 to 2005. The personal experiences of the author are obviously only reflected over these 40 years so that the glorious antecedents in the period up to 1933, the era in which our predecessors were the world leaders in neurology, is not sufficiently covered. This dominance was lost by the anti-Semitism during the era of National Socialism and the sequelae of World War II. As a result of the war, German neurologists became effectively isolated and their participation in international congresses was forbidden so that a gradual reestablishment of alignment only became possible after 1960. In this brief description no attempt at completeness has been made and only subjectivity and brevity have been considered. An attempt is made to retrospectively convey what essentially happened. An exact dating of advances over the period was sometimes difficult. The readership will have the opportunity to share the surprise of the author on how meagre the neurological knowledge and diagnostic methods were 50 years ago, how rapidly the subsequent development happened, how rapidly things became obvious which 20 years ago nobody was aware of and despite the progress how pleased we were to find ourselves at the most recent state of error and probably still find ourselves nowadays. In particular, how powerless and untested the therapeutic efforts were at that time. The progress can only be measured by a comparison between then, 50 years ago and the present. A projection of the future based on these experiences is not attempted but it seems to be certain that many conceptions, diagnostic advances and therapy options are still undiscovered and that further exciting times can be expected.
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Broser PJ, Braun C. Hydraulic Driven Fast and Precise Nonmagnetic Tactile Stimulator for Neurophysiological and MEG Measurements. IEEE Trans Biomed Eng 2012; 59:2852-8. [DOI: 10.1109/tbme.2012.2212191] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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Oxytocin attenuates feelings of hostility depending on emotional context and individuals' characteristics. Sci Rep 2012; 2:384. [PMID: 22540030 PMCID: PMC3337658 DOI: 10.1038/srep00384] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2012] [Accepted: 03/30/2012] [Indexed: 11/23/2022] Open
Abstract
In humans, oxytocin (OT) enhances prosocial behaviour. However, it is still unclear how the prosocial effects of OT are modulated by emotional features and/or individuals' characteristics. In a placebo-controlled design, we tested 20 healthy male volunteers to investigate these behavioural and neurophysiological modulations using magnetoencephalography. As an index of the individuals' characteristics, we used the empathy quotient (EQ), the autism spectrum quotient (AQ), and the systemising quotient (SQ). Only during the perception of another person's angry face was a higher SQ a significant predictor of OT-induced prosocial change, both in the behavioural and neurophysiological indicators. In addition, a lower EQ was only a significant predictor of OT-induced prosocial changes in the neurophysiological indicators during the perception of angry faces. Both on the behavioural and the neurophysiological level, the effects of OT were specific for anger and correlated with a higher SQ.
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Yamashiro K, Inui K, Otsuru N, Kakigi R. Change-related responses in the human auditory cortex: An MEG study. Psychophysiology 2010; 48:23-30. [DOI: 10.1111/j.1469-8986.2010.01038.x] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Tanaka E, Kida T, Inui K, Kakigi R. Change-driven cortical activation in multisensory environments: an MEG study. Neuroimage 2009; 48:464-74. [PMID: 19559795 DOI: 10.1016/j.neuroimage.2009.06.037] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2009] [Revised: 06/12/2009] [Accepted: 06/16/2009] [Indexed: 11/26/2022] Open
Abstract
The quick detection of dynamic changes in multisensory environments is essential to survive dangerous events and orient attention to informative events. Previous studies have identified multimodal cortical areas activated by changes of visual, auditory, and tactile stimuli. In the present study, we used magnetoencephalography (MEG) to examine time-varying cortical processes responsive to unexpected unimodal changes during continuous multisensory stimulation. The results showed that there were change-driven cortical responses in multimodal areas, such as the temporo-parietal junction and middle and inferior frontal gyri, regardless of the sensory modalities where the change occurred. These multimodal activations accompanied unimodal activations, both of which in general had some peaks within 300 ms after the changes. Thus, neural processes responsive to unimodal changes in the multisensory environment are distributed at different timing in these cortical areas.
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Affiliation(s)
- Emi Tanaka
- Department of Integrative Physiology, National Institute for Physiological Sciences, Myodaiji, Okazaki 444-8585, Japan.
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Hari R, Kujala MV. Brain basis of human social interaction: from concepts to brain imaging. Physiol Rev 2009; 89:453-79. [PMID: 19342612 DOI: 10.1152/physrev.00041.2007] [Citation(s) in RCA: 348] [Impact Index Per Article: 23.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Modern neuroimaging provides a common platform for neuroscience and related disciplines to explore the human brain, mind, and behavior. We base our review on the social shaping of the human mind and discuss various aspects of brain function related to social interaction. Despite private mental contents, people can share their understanding of the world using, beyond verbal communication, nonverbal cues such as gestures, facial expressions, and postures. The understanding of nonverbal messages is supported by the brain's mirroring systems that are shaped by individual experience. Within the organism-environment system, tight links exist between action and perception, both within an individual and between several individuals. Therefore, any comprehensive brain imaging study of the neuronal basis of social cognition requires appreciation of the situated and embodied nature of human cognition, motivating simultaneous monitoring of brain and bodily functions within a socially relevant environment. Because single-person studies alone cannot unravel the dynamic aspects of interpersonal interactions, it seems both necessary and beneficial to move towards "two-person neuroscience"; technological shortcomings and a limited conceptual framework have so far hampered such a leap. We conclude by discussing some major disorders of social interaction.
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Affiliation(s)
- Riitta Hari
- Brain Research Unit, Low Temperature Laboratory, Helsinki University of Technology, Espoo, Finland.
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References. Acta Neurol Scand 2009. [DOI: 10.1111/j.1600-0404.1993.tb04175.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Abstract
With increasing clinical experience, peripheral nerve surgeons have come to appreciate the important role that cortical plasticity and motor relearning play in functional recovery following a nerve transfer. Neurostimulation (transcranial magnetic stimulation), and neuroimaging (functional MRI, structural MRI, magnetoencephalography) measure different aspects of cortical physiology and when used together are powerful tools in the study of cortical plasticity. The mechanisms of cortical plasticity, according to current and widely accepted opinions, involve the unmasking of previously ineffective connections or the sprouting of intact afferents from adjacent cortical or subcortical territories. Although significant strides have been made in our understanding of cortical plasticity following nerve transfer and during motor relearning, a great deal remains that we do not understand. Cortical plasticity and its manipulation may one day become important contributors to improve functional outcome following nerve transfer.
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The effect of methylphenidate on auditory information processing in healthy volunteers: a combined EEG/MEG study. Psychopharmacology (Berl) 2008; 197:475-86. [PMID: 18264697 DOI: 10.1007/s00213-007-1065-8] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/19/2007] [Accepted: 12/19/2007] [Indexed: 01/09/2023]
Abstract
INTRODUCTION The psychomotor stimulant methylphenidate (MPH) has been shown to improve attentional processes, reflected in behavioural measures such as vigilance, reaction time and visual attention tasks. The neural mechanisms of MPH action on sensory information processing, however, remain poorly understood. To the authors' knowledge, this present study is the first to investigate whether a single dose of MPH affects neural substrates of passive attention in healthy adults studied with simultaneous whole-head magnetoencephalography (MEG) and electroencephalography (EEG). METHODS Monaural left-ear auditory stimuli were presented in an oddball paradigm with infrequent deviant tones differing in frequency and duration. Neuronal activity was recorded with simultaneous whole-head MEG and EEG in 13 healthy subjects (five females; aged 27 +/- 5 years) after oral administration of 40 mg MPH or placebo in a randomised, double-blind, cross-over design. We analysed both electric and magnetic N100, P200 and mismatch negativity (MMN) components. RESULTS MPH increased arousal levels in visual analogue scales. MPH had no effect on the dipole strength of MMN or MMNm in either frequency or duration deviations. MPH did, however, reduce P200 amplitudes in EEG. CONCLUSIONS The lack of effect of MPH on either MMN or MMNm suggests no association between catecholaminergic activities and MMN generation. However, our findings imply that MPH may change the neural bases of auditory information processing such as the early stimulus evaluation reflected in the P200 component. Dopamine and noradrenaline neurotransmitter systems could be responsible for the modulation of these processes. The exclusive effect of MPH on the P200 component could have a clinical application.
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Abstract
Voice onset time (VOT) provides an important auditory cue for recognizing spoken consonant-vowel syllables. Although changes in the neuromagnetic response to consonant-vowel syllables with different VOT have been examined, such experiments have only manipulated VOT with respect to voicing. We utilized the characteristics of a previously developed asymmetric VOT continuum [Liederman, J., Frye, R. E., McGraw Fisher, J., Greenwood, K., & Alexander, R. A temporally dynamic contextual effect that disrupts voice onset time discrimination of rapidly successive stimuli. Psychonomic Bulletin and Review, 12, 380-386, 2005] to determine if changes in the prominent M100 neuromagnetic response were linearly modulated by VOT. Eight right-handed, English-speaking, normally developing participants performed a VOT discrimination task during a whole-head neuromagnetic recording. The M100 was identified in the gradiometers overlying the right and left temporal cortices and single dipoles were fit to each M100 waveform. A repeated measures analysis of variance with post hoc contrast test for linear trend was used to determine whether characteristics of the M100 were linearly modulated by VOT. The morphology of the M100 gradiometer waveform and the peak latency of the dipole waveform were linearly modulated by VOT. This modulation was much greater in the left, as compared to the right, hemisphere. The M100 dipole moved in a linear fashion as VOT increased in both hemispheres, but along different axes in each hemisphere. This study suggests that VOT may linearly modulate characteristics of the M100, predominately in the left hemisphere, and suggests that the VOT of consonant-vowel syllables, instead of, or in addition to, voicing, should be examined in future experiments.
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Affiliation(s)
- Richard E Frye
- University of Texas Health Science Center at Houston, TX 77030, USA.
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Rossini PM, Rossi S, Babiloni C, Polich J. Clinical neurophysiology of aging brain: from normal aging to neurodegeneration. Prog Neurobiol 2007; 83:375-400. [PMID: 17870229 DOI: 10.1016/j.pneurobio.2007.07.010] [Citation(s) in RCA: 333] [Impact Index Per Article: 19.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2007] [Revised: 05/03/2007] [Accepted: 07/26/2007] [Indexed: 02/06/2023]
Abstract
Physiological brain aging is characterized by a loss of synaptic contacts and neuronal apoptosis that provokes age-dependent decline of sensory processing, motor performance, and cognitive function. Neural redundancy and plastic remodelling of brain networking, also secondary to mental and physical training, promotes maintenance of brain activity in healthy elderly for everyday life and fully productive affective and intellectual capabilities. However, age is the main risk factor for neurodegenerative disorders such as Alzheimer's disease (AD) that impact on cognition. Oscillatory electromagnetic brain activity is a hallmark of neuronal network function in various brain regions. Modern neurophysiological techniques including electroencephalography (EEG), event-related potential (ERP), magnetoencephalography (MEG), and transcranial magnetic stimulation (TMS) can accurately index normal and abnormal brain aging to facilitate non-invasive analysis of cortico-cortical connectivity and neuronal synchronization of firing and coherence of rhythmic oscillations at various frequencies. The present review provides a perspective of these issues by assaying different neurophysiological methods and integrating the results with functional brain imaging findings. It is concluded that discrimination between physiological and pathological brain aging clearly emerges at the group level, with applications at the individual level also suggested. Integrated approaches utilizing neurophysiological techniques together with biological markers and structural and functional imaging are promising for large-scale, low-cost and non-invasive evaluation of at-risk populations. Practical implications of the methods are emphasized.
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Affiliation(s)
- Paolo M Rossini
- Clinica Neurologica University Campus Bio-Medico, Rome, Italy.
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Rovati L, Salvatori G, Bulf L, Fonda S. Optical and electrical recording of neural activity evoked by graded contrast visual stimulus. Biomed Eng Online 2007; 6:28. [PMID: 17610733 PMCID: PMC1934360 DOI: 10.1186/1475-925x-6-28] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2007] [Accepted: 07/04/2007] [Indexed: 11/12/2022] Open
Abstract
Background Brain activity has been investigated by several methods with different principles, notably optical ones. Each method may offer information on distinct physiological or pathological aspects of brain function. The ideal instrument to measure brain activity should include complementary techniques and integrate the resultant information. As a "low cost" approach towards this objective, we combined the well-grounded electroencephalography technique with the newer near infrared spectroscopy methods to investigate human visual function. Methods The article describes an embedded instrumentation combining a continuous-wave near-infrared spectroscopy system and an electroencephalography system to simultaneously monitor functional hemodynamics and electrical activity. Near infrared spectroscopy (NIRS) signal depends on the light absorption spectra of haemoglobin and measures the blood volume and blood oxygenation regulation supporting the neural activity. The NIRS and visual evoked potential (VEP) are concurrently acquired during steady state visual stimulation, at 8 Hz, with a b/w "windmill" pattern, in nine human subjects. The pattern contrast is varied (1%, 10%, 100%) according to a stimulation protocol. Results In this study, we present the measuring system; the results consist in concurrent recordings of hemodynamic changes and evoked potential responses emerging from different contrast levels of a patterned stimulus. The concentration of [HbO2] increases and [HHb] decreases after the onset of the stimulus. Their variation shows a clear relationship with the contrast value: large contrast produce huge difference in concentration, while low contrast provokes small concentration difference. This behaviour is similar to the already known relationship between VEP response amplitude and contrast. Conclusion The simultaneous recording and analysis of NIRS and VEP signals in humans during visual stimulation with a b/w pattern at variable contrast, demonstrates a strong linear correlation between hemodynamic changes and evoked potential amplitude. Furthermore both responses present a logarithmic profile with stimulus contrast.
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Affiliation(s)
- Luigi Rovati
- Department of Information Engineering, University of Modena and Reggio Emilia, Via Vignolese 905, I-41100 Modena, Italy
| | - Giorgia Salvatori
- Department of Information Engineering, University of Modena and Reggio Emilia, Via Vignolese 905, I-41100 Modena, Italy
| | - Luca Bulf
- Department of Biomedical Sciences, University of Modena and Reggio Emilia, Via Campi 287, I-41100 Modena, Italy
| | - Sergio Fonda
- Department of Biomedical Sciences, University of Modena and Reggio Emilia, Via Campi 287, I-41100 Modena, Italy
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Korostenskaja M, Nikulin VV, Kicić D, Nikulina AV, Kähkönen S. Effects of NMDA receptor antagonist memantine on mismatch negativity. Brain Res Bull 2007; 72:275-83. [PMID: 17452287 DOI: 10.1016/j.brainresbull.2007.01.007] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2006] [Revised: 12/03/2006] [Accepted: 01/03/2007] [Indexed: 10/23/2022]
Abstract
Mismatch negativity (MMN) and its magnetic counterpart (MMNm) have been shown to be altered in patients with various psychiatric and neurological disorders, e.g. Alzheimer's disease and schizophrenia, indicating deficits in involuntary attention. N-Methyl-D-aspartate (NMDA) receptor-mediated glutamate dysfunction is suggested to underlie these deficits. However, the role of NMDA receptors in involuntary attention is poorly understood. Memantine is an NMDA receptor antagonist that has been demonstrated to be effective in the treatment of patients with Alzheimer's disease. We aimed to investigate whether a single dose of memantine would affect MMN/MMNm in healthy subjects studied with simultaneous electroencephalography (EEG) and magnetoencephalography (MEG). Monaural left-ear auditory stimuli were presented in a passive oddball paradigm with infrequent deviant tones differing in frequency and duration. Neuronal activity was recorded in 13 healthy subjects after oral administration of 30mg of memantine or placebo in a randomized, double-blind, cross-over design. MMNm was analyzed using equivalent current dipoles. MMN was evaluated from frontocentral electrodes. Memantine lowered subjects' arousal level as measured by visual analog scales, and enhanced the amplitude of MMN in EEG. No differences in MMN latency were observed in MEG or EEG. Memantine did not affect the location, strength, amplitude or latency of MMNm, P1m, and N1m components. No changes in amplitude or latency were observed for P1 and N1 peaks. These results indicate that memantine affects involuntary attention without otherwise changing auditory processing of the stimuli. As memantine-induced changes in MMN were detected only in EEG, we suggest that the effect is mostly related to the frontal cortex.
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Tyc F, Boyadjian A. Cortical plasticity and motor activity studied with transcranial magnetic stimulation. Rev Neurosci 2007; 17:469-95. [PMID: 17180875 DOI: 10.1515/revneuro.2006.17.5.469] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
For decades cortical representations of the parts of the body have been considered to be unchangeable. This view has changed radically during the past 20 years using new tools designed to study plasticity in the adult human brain. Transcranial magnetic stimulation (TMS) is a valuable non-invasive technique for exploring the ability of the motor cortex to change during motor skill acquisition. Results obtained with TMS in neurological patients as well as in normal subjects demonstrate that cortical plasticity is a necessity for correct adaptation to the continuously changing environment. Topographical reorganization of the motor cortex depends on the types of movements performed by the subjects. During simple training, the cortical representation is enlarged, and it returns to its initial size when the task is overlearned. These transient modifications characterize simple motor training. Motor skills in which coordination of distal and proximal muscles, precision of the task and spatio-temporal constraints are associated, has a different impact on cortical reorganization. We propose that years of practice of a complex motor skill induces a new cortical topography that must be interpreted as structural plasticity which provides the capacity to execute a plastic behaviour instead of a stereotypical movement. We review the neuronal mechanisms underlying plasticity in different types of movement. We stress new emerging notions, such as overlap of cortical maps, and system dynamics at single neuron and network levels, to explain the reorganization of movement representations that encode motor skill. Dendritic arborizations as functional computing elements, newly generated neurons in adult brain, and plastic architectures of cortical networks operating as distributed functional modules are new hypotheses for structural plasticity.
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Affiliation(s)
- François Tyc
- Université du Littoral-Côte d'Opale, Calais, France.
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Rodríguez-Rivera A, Baryshnikov BV, Van Veen BD, Wakai RT. MEG and EEG Source Localization in Beamspace. IEEE Trans Biomed Eng 2006; 53:430-41. [PMID: 16532769 DOI: 10.1109/tbme.2005.869764] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Beamspace methods are applied to EEG/MEG source localization problems in this paper. Beamspace processing involves passing the data through a linear transformation that reduces the data dimension prior to applying a desired statistical signal processing algorithm. This process generally reduces the data requirements of the subsequent algorithm. We present one approach for designing beamspace transformations that are optimized to preserve source activity located within a given region of interest and show that substantial reductions in dimension are obtained with negligible signal loss. Beamspace versions of maximum likelihood dipole fitting, MUSIC, and minimum variance beamforming source localization algorithms are presented. The performance improvement offered by the beamspace approach with limited data is demonstrated by bootstrapping somatosensory data to evaluate the variability of the source location estimates obtained with each algorithm. The quantitative benefits of beamspace processing depend on the algorithm, signal to noise ratio, and amount of data. Dramatic performance improvements are obtained in scenarios with low signal to noise ratio and a small number of independent data samples.
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Affiliation(s)
- Alberto Rodríguez-Rivera
- Department of Electrical and Computer Engineering, University of Wisconsin-Madison, 1415 Engineering Drive, Madison, WI 53706, USA.
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Simon JZ, Wang Y. Fully complex magnetoencephalography. J Neurosci Methods 2005; 149:64-73. [PMID: 16026851 DOI: 10.1016/j.jneumeth.2005.05.005] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2005] [Revised: 05/03/2005] [Accepted: 05/05/2005] [Indexed: 11/20/2022]
Abstract
Complex numbers appear naturally in biology whenever a system can be analyzed in the frequency domain, such as physiological data from magnetoencephalography (MEG). For example, the MEG steady state response to a modulated auditory stimulus generates a complex magnetic field for each MEG channel, equal to the Fourier transform at the stimulus modulation frequency. The complex nature of these data sets, often not taken advantage of, is fully exploited here with new methods. Whole-head, complex magnetic data can be used to estimate complex neural current sources, and standard methods of source estimation naturally generalize for complex sources. We show that a general complex neural vector source is described by its location, magnitude, and direction, but also by a phase and by an additional perpendicular component. We give natural interpretations of all the parameters for the complex equivalent-current dipole by linking them to the underlying neurophysiology. We demonstrate complex magnetic fields, and their equivalent fully complex current sources, with both simulations and experimental data.
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Affiliation(s)
- Jonathan Z Simon
- Department of Electrical and Computer Engineering, University of Maryland, College Park, MD 20742, USA.
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Nikulin VV, Nikulina AV, Yamashita H, Rossi EM, Kähkönen S. Effects of alcohol on spontaneous neuronal oscillations: a combined magnetoencephalography and electroencephalography study. Prog Neuropsychopharmacol Biol Psychiatry 2005; 29:687-93. [PMID: 15905011 DOI: 10.1016/j.pnpbp.2005.04.014] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 04/06/2005] [Indexed: 11/17/2022]
Abstract
Electroencephalography (EEG) and magnetoencephalography (MEG) can detect different aspects of alcohol effects on auditory processing measured with event-related potentials and magnetic fields. The present study aimed to detect alcohol-induced changes in spontaneous neuronal oscillations with combined EEG and MEG techniques. The effects of alcohol on spontaneous neuronal rhythms were studied in 12 healthy subjects after 0.8 g/kg alcohol or juice in a double-blind, placebo-controlled, cross-over design using simultaneous high-resolution MEG and EEG in eyes-open and eyes-closed conditions. The data were analyzed with a power spectral density analysis. MEG recording showed that alcohol significantly increased the relative power of alpha rhythm (8-10 Hz) and reduced the relative power of beta activity (17-25 Hz) in both left and right hemispheres, but only in the eyes-closed condition. These effects did not depend on gender. No analogous statistically significant changes were observed in EEG rhythms. However, the power of alpha and beta rhythms was positively correlated in MEG and EEG recordings, indicating that MEG and EEG reflect similar processes. A distinct sensitivity of MEG and EEG to the sources of cortical oscillations, a better signal-to-noise ratio of MEG, as well as strong spatial blurring of potentials in EEG are most likely the reasons for the observed differences in the effects of alcohol on spontaneous oscillations as detected with two methods.
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Affiliation(s)
- Vadim V Nikulin
- BioMag Laboratory, Engineering Center, Helsinki University Central Hospital, P.O. Box 340, FIN-00029 HUS, Finland
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Kettenmann B, Feichtinger M, Tilz C, Kaltenhäuser M, Hummel C, Stefan H. Comparison of clonidine to sleep deprivation in the potential to induce spike or sharp-wave activity. Clin Neurophysiol 2005; 116:905-12. [PMID: 15792900 DOI: 10.1016/j.clinph.2004.11.006] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2004] [Revised: 09/20/2004] [Accepted: 11/03/2004] [Indexed: 11/26/2022]
Abstract
OBJECTIVE This study aimed to investigate previously observed side effects, i.e. increased epileptic activity during clonidine medication. The safety and effectiveness of clonidine as spike inducing agent compared to sleep deprivation were tested. METHODS Patients suffering from drug-resistant localization related epilepsy took part in 3 magnetoencephalography (MEG) sessions. One session was recorded without any activating measures. The other two sessions were either performed after sleep deprivation or after medication with clonidine. Target parameter was the number of spikes or sharp-waves during a 30 min recording period. RESULTS About 67% of the patients showed increased spike activity after clonidine, whereas sleep deprivation increased the number of spikes in 33%, and 29% of the patients did not show any activation at all. Clonidine was most effective in temporal lobe epilepsy, when the focus was located in the right hemisphere, and when clonidine serum concentrations were ranging between 0.6 and 1.0 ng/ml. CONCLUSIONS This study showed for the first time that clonidine can be considered an effective spike or sharp-wave inducing drug that is superior to the potency of sleep deprivation. SIGNIFICANCE The administration of clonidine increases the probability of recording ictal and interictal epileptic activity during limited acquisition time.
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Affiliation(s)
- B Kettenmann
- Department of Neurology, University of Erlangen-Nuremberg, Erlangen, Germany.
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Kähkönen S, Mäkinen V, Jääskeläinen IP, Pennanen S, Liesivuori J, Ahveninen J. Serotonergic modulation of mismatch negativity. Psychiatry Res 2005; 138:61-74. [PMID: 15708302 DOI: 10.1016/j.pscychresns.2004.09.006] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/16/2003] [Revised: 08/12/2004] [Accepted: 09/20/2004] [Indexed: 11/21/2022]
Abstract
Neurochemical mechanisms mediating the interaction between emotional and cognitive processing are not yet fully understood. Here, we utilized acute tryptophan depletion (ATD) to reduce the brain synthesis of serotonin (5-HT), which is thought to have a central role in regulation of emotions and mood in humans. ATD effects on event-related potentials and magnetic fields were studied using a passive odd-ball paradigm in a randomized, double-blinded, controlled, cross-over design. Auditory responses were recorded simultaneously with high-resolution magnetoencephalography (MEG) and electroencephalography (EEG) in 14 healthy subjects, 5 h after ATD or a control condition. ATD significantly increased depressed mood and lowered plasma tryptophan concentration (total tryptophan decreased by 75%, free tryptophan decreased by 39%). As compared with the control condition, ATD increased the amplitudes of mismatch negativity (MMN) to duration and frequency changes and decreased the latencies of magnetic MMN to frequency changes in the hemisphere ipsilateral to the ear stimulated. Further, ATD modulated N1m latencies and decreased P2m source activity. ATD increased the interhemispheric latency difference of MMNm to frequency changes. No effects on P50 were observed. The present results suggest serotonergic modulation of preattentive auditory change detection, suggested to initiate involuntary attention shifting in the human brain.
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Affiliation(s)
- Seppo Kähkönen
- Cognitive Brain Research Unit, University of Helsinki, Finland.
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Mäkelä JP, Ahonen A, Hämäläinen M, Hari R, Llmoniemi R, Kajola M, Knuutila J, Lounasmaa OV, McEvoy L, Salmelin R, Salonen O, Sams M, Simola J, Tesche C, Vasama JP. Functional differences between auditory cortices of the two hemispheres revealed by whole-head neuromagnetic recordings. Hum Brain Mapp 2004. [DOI: 10.1002/hbm.460010106] [Citation(s) in RCA: 95] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022] Open
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Kujala A, Alho K, Service E, Ilmoniemi RJ, Connolly JF. Activation in the anterior left auditory cortex associated with phonological analysis of speech input: localization of the phonological mismatch negativity response with MEG. ACTA ACUST UNITED AC 2004; 21:106-13. [PMID: 15325418 DOI: 10.1016/j.cogbrainres.2004.05.011] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/28/2004] [Indexed: 10/26/2022]
Abstract
The spatio-temporal dynamics of cortical activation underlying auditory word recognition, particularly its phonological stage, was studied with whole-head magnetoencephalography (MEG). Subjects performed a visuo-auditory priming task known to evoke the phonological mismatch negativity (PMN) response that is elicited by violations of phonological expectancies. Words and non-words were presented in separate conditions. In each of the 318 trials, the subjects first saw a word/non-word (e.g., 'cat') that was soon followed by a prime letter (e.g., 'h'). Their task was to replace mentally the sound of the first letter of the word/non-word with the prime letter, thus resulting in a new word/non-word (e.g., 'hat'). Finally, an auditory word/non-word either matching or mismatching with the anticipated item was presented. In most subjects, a PMNm followed by a later, N400m-like negativity was obtained in the left hemisphere to the mismatching auditory stimuli. A similar response pattern was obtained in the right hemisphere only in a few subjects. Source localization of the N1m, an index of acoustic analysis, and the PMNm and N400m-like responses was performed using L1 minimum-norm estimation. In the left hemisphere, the PMNm source for the words was significantly more anterior than the source of the N400m-like response; for the non-words, the PMNm source was significantly more anterior than the sources of the N1m and the N400m-like response. These results suggest that the left-hemisphere neuronal networks involved in sub-lexical phonological analysis are at least partly different from those responsible for the earlier (acoustic) and later (whole item) processing of speech input.
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Affiliation(s)
- Anu Kujala
- Cognitive Brain Research Unit, Department of Psychology, University of Helsinki, PO Box 9, FIN-00014, Finland.
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Weems SA, Zaidel E, Berman S, Mandelkern MA. Asymmetry in alpha power predicts accuracy of hemispheric lexical decision. Clin Neurophysiol 2004; 115:1575-82. [PMID: 15203058 DOI: 10.1016/j.clinph.2004.02.020] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/21/2004] [Indexed: 10/26/2022]
Abstract
OBJECTIVE Previous work has shown that individual differences in resting alpha asymmetry are associated with efficacy on a variety of cognitive tasks. Still unresolved is how ongoing alpha asymmetry relates to behavioral asymmetry, explored here using lateralized lexical decision. METHODS Alpha power immediately preceding lexical decision trials was measured to assess cognitive engagement during word recognition. This was compared with behavioral performance for the task, measured by accuracy and latency of the lexical decision response. RESULTS Greater relative left hemisphere alpha power (i.e. higher asymmetry) immediately before presentation of a word led to reduced likelihood for its successful identification. Greater alpha asymmetry was also associated with reduced performance for identifying stimuli lateralized to the right visual field. CONCLUSIONS Word recognition is facilitated by decreased asymmetry in cognitive engagement in the two cerebral hemispheres, particularly when the stimuli are lateralized to the left hemisphere (right visual field). SIGNIFICANCE Results address the role of cognitive engagement in the two cerebral hemispheres, and its relationship with lexical access.
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Affiliation(s)
- Scott A Weems
- Department of Computer Science, University of Maryland at College Park, A.V. Williams Building, College Park, MD 20742, USA.
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Kubota T, Kaneoke Y, Maruyama K, Watanabe K, Kakigi R. Temporal structure of the apparent motion perception: a magnetoencephalographic study. Neurosci Res 2004; 48:111-8. [PMID: 14687887 DOI: 10.1016/j.neures.2003.10.006] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
Humans perceive motion when numerous small dots pattern is followed by one of the same pattern but with all the dots shifted a little in one direction. When the amount of shift exceeds a level humans no more perceive motion even though physical visual information does not change. Using this stimulus, we addressed to elucidate the temporal structure of the neural activity related to this apparent motion perception. The magnetic responses to the random-dot patterns with various amounts of shift were measured while the subjects were performing a direction discrimination task. A significant magnetic response amplitude change occurred with three distinct peaks when the response inducing apparent motion was compared with those inducing no motion without change in the response latencies. The major difference occurred at about 110, 140, 210 ms after the stimulus onset. The response origin was always within the occipitotemporal area. The results indicate that the neural activity for the perception of apparent motion can be measured by MEG that occur at least 110 ms after the stimulus onset possibly in the human MT+. Three distinct peaks in the response difference may represent the sequential multiple neural process proposed theoretically though further study is necessary to prove.
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Affiliation(s)
- Tetsuo Kubota
- Department of Integrative Physiology, National Institute for Physiological Sciences, Myodaiji-cho, Okazaki 444-8585, Japan
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Wydell TN, Vuorinen T, Helenius P, Salmelin R. Neural Correlates of Letter-String Length and Lexicality during Reading in a Regular Orthography. J Cogn Neurosci 2003; 15:1052-62. [PMID: 14614815 DOI: 10.1162/089892903770007434] [Citation(s) in RCA: 85] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Abstract
Abstract
Behavioral studies have shown that short letter strings are read faster than long letter-strings and words are read faster than nonwords. Here, we describe the dynamics of letter-string length and lexicality effects at the cortical level, using magnetoencephalography, during a reading task in Finnish with long (eight-letter) and short (four-letter) word/nonword stimuli. Length effects were observed in two spatially and temporally distinct cortical activations: (1) in the occipital cortex at about 100 msec by the strength of activation, regardless of the lexical status of the stimuli, and (2) in the left superior temporal cortex between 200 and 600 msec by the duration of activation, with words showing a smaller effect than nonwords. A significant lexicality effect was also evident in this later activation, with stronger activation and longer duration for nonwords than words. There seem to be no distinct cortical areas for reading words and nonwords. The early length effect is likely to be due to the low-level visual analysis common to all stimulus letter-strings. The later lexicality and length effects apparently reflect converging lexico-semantic and phonological influences, and are discussed in terms of dual-route and single-route connectionist models of reading.
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Affiliation(s)
- T N Wydell
- Department of Human Sciences, Brunel University, Uxbridge, Middlesex, UK.
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McKenzie AL, Nagarajan SS, Roberts TPL, Merzenich MM, Byl NN. Somatosensory Representation of the Digits and Clinical Performance in Patients with Focal Hand Dystonia. Am J Phys Med Rehabil 2003; 82:737-49. [PMID: 14508403 DOI: 10.1097/01.phm.0000087458.32122.14] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
OBJECTIVE The purpose of this study was to incorporate magnetoencephalography and clinical testing to describe differences in somatosensory organization and sensorimotor function of the hand in patients with focal hand dystonia, a target-specific disorder of voluntary movement that interferes with fine motor control during the performance of rapid, repetitive, skilled movements. DESIGN This descriptive study included prospective, quasi-experimental comparisons between groups. RESULTS Patients with focal hand dystonia demonstrated deficits in physical variables, sensory processing, and motor control when compared with age- and sex-matched controls. They also had altered patterns of firing (amplitude and latency integrated over time) and abnormal somatosensory representations on magnetoencephalography. CONCLUSIONS These study findings suggest that there are alterations in both somatosensory representation of the digits and clinical performance in patients with focal hand dystonia. Future studies to determine if alterations in the sensorimotor feedback loop contribute to the development of focal hand dystonia are indicated. If so, intervention strategies may need to include specific types of somatosensory retraining as part of the rehabilitation program for patients with focal hand dystonia.
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Affiliation(s)
- A L McKenzie
- Department of Physical Therapy, Chapman University, Orange, California 92866, USA
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31
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Kähkönen S, Ahveninen J, Pekkonen E, Kaakkola S, Huttunen J, Ilmoniemi RJ, Jääskeläinen IP. Dopamine modulates involuntary attention shifting and reorienting: an electromagnetic study. Clin Neurophysiol 2002; 113:1894-902. [PMID: 12464326 DOI: 10.1016/s1388-2457(02)00305-x] [Citation(s) in RCA: 104] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
OBJECTIVE Dopaminergic function has been closely associated with attentional performance, but its precise role has remained elusive. METHODS Electrophysiological and behavioral methods were used to assess the effects of dopamine D2-receptor antagonist haloperidol on involuntary attention shifting using a randomized, double-blind, placebo-controlled cross-over design. Eleven subjects were instructed to discriminate equiprobable 200 and 400ms tones in a forced-choice reaction-time (RT) task during simultaneous measurement of whole-head magnetoencephalography and high-resolution electroencephalography. RESULTS Occasional changes in task-irrelevant tone frequency (10% increase or decrease) caused marked distraction on behavioral performance, as shown by significant RT increases to deviant stimuli and subsequent standard tones. Furthermore, while the standard tones elicited distinct P1-N1-P2-N2-P3 waveforms, deviant tones elicited additional mismatch negativity (MMN), P3a, and reorienting negativity (RON) responses, indexing brain events associated with involuntary attention shifting. While haloperidol did not affect the source loci of the responses of magnetic N1 and MMN, the amplitude of the electric P3a and that of RON were significantly reduced and the latency of magnetic RON were delayed following haloperidol administration. CONCLUSIONS The present results suggest that dopamine modulates involuntary attention shifting to task-irrelevant deviant events. It appears that dopamine may disrupt the subsequent re-orienting efforts to the relevant task after distraction.
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Affiliation(s)
- Seppo Kähkönen
- Cognitive Brain Research Unit, Department of Psychology, University of Helsinki, Helsinki, Finland.
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32
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Hertrich I, Mathiak K, Lutzenberger W, Ackermann H. Hemispheric lateralization of the processing of consonant-vowel syllables (formant transitions): effects of stimulus characteristics and attentional demands on evoked magnetic fields. Neuropsychologia 2002; 40:1902-17. [PMID: 12207989 DOI: 10.1016/s0028-3932(02)00063-5] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
It is still unsettled in how far temporal resolution of dynamic acoustic events (formant transitions) or phonetic/linguistic processes contribute to predominant left-hemisphere encoding of consonant-vowel syllables. To further elucidate the underlying mechanisms, evoked magnetic fields in response to consonant-vowel events (synthetic versus spoken) were recorded (oddball design: standards=binaural/ba/, deviants=dichotic/ba/-/da/; 20 right-handed subjects) under different attentional conditions (visual distraction versus stimulus identification). Spoken events yielded a left-lateralized peak phase of the mismatch field (MMF; 150-200ms post-stimulus onset) in response to right-ear deviants during distraction. By contrast, pre-attentive processing of synthetic items gave rise to a left-enhanced MMF onset (100ms), but failed to elicit later lateralization effects. In case of directed attention, synthetic deviants elicited a left-pronounced MMF peak resembling the pre-attentive response to natural syllables. These interactions of MMF asymmetry with signal structure and attentional load indicate two distinct successive left-lateralization effects: signal-related operations and representation of 'phonetic traces'. Furthermore, a right-lateralized early MMF component (100ms) emerged in response to natural syllables during pre-attentive processing and to synthetic stimuli in case of directed attention. Conceivably, these effects indicate right hemisphere operations prior to phonetic evaluation such as periodicity representation. Two distinct time windows showed correlations between dichotic listening performance and ear effects on magnetic responses reflecting early gain factors (ca. 75ms post-stimulus onset) and binaural fusion strategies (ca. 200ms), respectively. Finally, gender interacted with MMF lateralization, indicating different processing strategies in case of artificial speech signals.
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Affiliation(s)
- Ingo Hertrich
- Department of Neurology, University of Tübingen, Otfried-Müller-Street 47, Germany.
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Mathiak K, Hertrich I, Lutzenberger W, Ackermann H. Functional cerebral asymmetries of pitch processing during dichotic stimulus application: a whole-head magnetoencephalography study. Neuropsychologia 2002; 40:585-93. [PMID: 11792400 DOI: 10.1016/s0028-3932(01)00159-2] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Dichotic listening (DL) studies indicate higher proficiency of the right cerebral hemisphere in processing the pitch of auditory events. Especially, acoustic stimuli of a rich harmonic structure such as square waves (complex tones) elicit a left ear advantage (LEA) under dichotic stimulus application. In order to investigate the timing of early sensory encoding at the level of the supratemporal plane, whole-head magnetoencephalography (MEG; 151 channels) recordings were performed in 20 right-handed subjects using an oddball paradigm based on dichotically applied complex tones. In contrast to electroencephalography (EEG) and event related potentials (ERP), this technique separately measures neuronal activity of left and right auditory cortex. Neuromagnetic responses were obtained both during preattentive stimulus processing, as well as during a pitch detection task. Rare stimuli presented to the left ear elicited a stronger magnetic analogue of mismatch negativity (MMNm) over both hemispheres and gave rise to shorter latencies of the contralateral mismatch fields than right ear deviants. In conclusion, the present data provide first evidence for functional laterality effects even at the level of preattentive pitch processing within the auditory cortex.
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Affiliation(s)
- Klaus Mathiak
- Department of Neurology, University of Tübingen, Hoppe-Seyler-Strasse 3, 72076 Tübingen, Germany.
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Miettinen R, Hasu M. Articulating User Needs in Collaborative Design: Towards an Activity-Theoretical Approach. Comput Support Coop Work 2002. [DOI: 10.1023/a:1015256909032] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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Wang L, Barber C, Kakigi R, Kaneoke Y, Okusa T, Wen Y. A first comparison of the human multifocal visual evoked magnetic field and visual evoked potential. Neurosci Lett 2001; 315:13-6. [PMID: 11711203 DOI: 10.1016/s0304-3940(01)02302-3] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
Our objectives were to determine the feasibility of recording reliable multifocal visual evoked magnetic fields (mfVEFs), to investigate the maximum stimulus eccentricity for which the mfVEF responses can be obtained, and to study how this changes with checksize (spatial frequency tuning). Using a checksize of 30', we recorded 8-channel pattern-onset mfVEFs three times to obtain responses from 19 channels located around the inion. Multifocal visual evoked potentials (mfVEPs) were recorded under the same conditions. Eccentricity changes with spatial frequency were studied using checksizes from 7.5' to 60'. We obtained, for the first time, reliable mfVEFs, and found they could be elicited from more peripheral stimulus elements than could mfVEPs. The larger the checksize, the greater the eccentricity reached.
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Affiliation(s)
- L Wang
- Department of Integrative Physiology, National Institute for Physiological Sciences, Myodaiji, 444-8585, Okazaki, Japan.
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Abstract
This paper presents an overview of a new method for the non-invasive measurement of brain function, the event-related optical signal (EROS). This technique is based on measures of the optical properties of cortical brain tissue, which change while the tissue is active. These changes are likely to be due to changes in light scattering, and are very rapid and localized, being related to phenomena occurring within or around the neuronal membrane. EROS, therefore yields images of cortical activity that combine spatial specificity (i.e. they can be related to patches of tissue less than a cubic centimeter in size) with temporal resolution (i.e. they depict the time course of the neural activity in the cortical areas under measurement). A limitation of this technique is its reduced penetration into the head (less than 3-5 cm). EROS appears to be a suitable technique for studying the time course of activity in selected cortical areas, and for providing a bridge between hemodynamic and electrophysiological imaging methods.
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Affiliation(s)
- G Gratton
- Beckman Institute, University of Illinois, Urbana, IL 61801, USA.
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Ackermann H, Hertrich I, Mathiak K, Lutzenberger W. Contralaterality of cortical auditory processing at the level of the M50/M100 complex and the mismatch field: a whole-head magnetoencephalography study. Neuroreport 2001; 12:1683-7. [PMID: 11409739 DOI: 10.1097/00001756-200106130-00033] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Humans show a stronger cortical representation of auditory input at the opposite hemisphere each. To specify the temporal aspects of this contralaterality effect within the domain of speech stimuli, the present study recorded a series of evoked magnetic fields (M50, M100, mismatch field) subsequent to monaural application of stop consonant-vowel syllables using whole-head magnetoencephalography (MEG). The M50 components exhibited a skewed shape of cross-symmetrical distribution in terms of an initial maximum peak succeeded by a knot over the contralateral and a reversed pattern over the ipsilateral temporal lobe. Most presumably, this pattern of evoked fields reflects two distinct stages of central-auditory processing: (a) initial excitation of the larger contralateral and the smaller ipsilateral projection area of the stimulated ear; (b) subsequent transcallosal activation of the residual neurons, i.e. the targets of the non-stimulated ear, at either side. Previous studies using non-speech stimuli found contralaterality of central-auditory processing to extend to the M100 field. In contrast, a larger amplitude of ipsilateral M100 as compared to the respective opposite deflection emerged after stimulation of either ear. Finally, the computed magnetic analogues of mismatch negativity failed any significant laterality effects. These data provide first evidence for a distinct pattern of hemispheric differences at the level of the M50/M100 complex subsequent to monaural application of speech stimuli.
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Affiliation(s)
- H Ackermann
- Department of Neurology, University of Tuebingen, Germany
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Mathiak K, Hertrich I, Lutzenberger W, Ackermann H. Neural correlates of duplex perception: a whole-head magnetencephalography study. Neuroreport 2001; 12:501-6. [PMID: 11234753 DOI: 10.1097/00001756-200103050-00015] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Simultaneous experience of the same acoustic stimulus in two distinct phenomenological modes, e.g. as a speech-like and as a non-speech event, is referred to as duplex perception (DP). The most widely investigated DP paradigm splits each of the stop consonant-vowel (CV) syllables /ga/ and /da/ into an isolated formant transient (chirp) and the remaining sound structure (base). The present study recorded mismatch fields in response to a series of dichotically applied base and chirp components using whole-head magnetencephalography (MEG). Preattentive mismatch fields showed larger amplitudes in response to contralateral deviants. During attention to the fused percept /da/, the left ear deviants chirps elicited an enhanced and posteriorly shifted dipole field over the ipsilateral hemisphere. These data provide first neurophysiological evidence that the integration of acoustic stimulus elements into a coherent syllable representation constitutes a distinct stage of left-hemisphere speech sound encoding.
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Affiliation(s)
- K Mathiak
- Department of Neurology, University of Tübingen, Germany
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Kaiser J, Lutzenberger W, Birbaumer N. Simultaneous bilateral mismatch response to right- but not leftward sound lateralization. Neuroreport 2000; 11:2889-92. [PMID: 11006960 DOI: 10.1097/00001756-200009110-00012] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Magnetoencephalography (MEG) was used to compare mismatch responses between hemispheres to changes in sound-source direction. Sixteen adults listened passively to two types of complex non-language sounds presented in separate blocks with midline standards and right- and left-lateralized deviants. Mismatch dipole amplitudes were larger contra- than ipsilaterally to the deviants. Both hemispheres processed right deviants simultaneously, whereas to left deviants, the left dipole peaked 20 ms later than the right dipole. A second experiment using the same standards but midline spectral deviants showed no interhemispheric differences. Here mismatch latencies were about 60 ms longer than in the location mismatch experiment. This suggested both fast, contralaterally dominant location mismatch responses and facilitated detection of auditory spatial deviance in the right hemifield.
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Affiliation(s)
- J Kaiser
- MEG Center, Institute of Medical Psychology and Behavioral Neurobiology, University of Tübingen, Germany
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Mathiak K, Hertrich I, Lutzenberger W, Ackermann H. Encoding of temporal speech features (formant transients) during binaural and dichotic stimulus application: a whole-head magnetencephalography study. BRAIN RESEARCH. COGNITIVE BRAIN RESEARCH 2000; 10:125-31. [PMID: 10978700 DOI: 10.1016/s0926-6410(00)00035-5] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Spoken-word recognition depends upon the encoding of relevant 'information bearing elements' of the acoustic speech signal. For example, relatively rapid shifts of spectral energy distribution (formant transients) cue the perception of stop consonant-vowel (CV) syllables such as /ba/, /ga/, and /da/. A variety of data indicate left-hemisphere superiority with respect to the processing of formant transients. To further delineate the underlying neurophysiological mechanisms, evoked cortical fields in response to CV syllables (oddball design; frequent stimulus=binaural /ga/; four deviant constellations: Binaural /ba/, binaural /da/, left /da/ (left ear deviant)-right /ga/, right /da/ (right ear deviant)-left /ga/) were recorded by means of whole-head magnetencephalography (MEG; 151 channels) under two different conditions of attentional demands (visual distraction versus reaction to prespecified stimuli). (a) During binaural stimulus presentation attention toward target events resulted in a significantly enhanced mismatch field (MMNm, magnetic analogue to the mismatch negativity) over the left as compared to the right hemisphere. In contrast, preattentive processing of the CV syllables failed MMNm lateralization effects. (b) Dichotic application of /da/ elicited a larger contralateral MMNm amplitude in subjects with right ear advantage (REA) at behavioral testing. In addition, right ear deviants yielded a stronger ipsilateral response than the left ear cognates. Taken together, these data indicate bilateral preattentive processing and subsequent attention-related predominant left-hemisphere encoding of formant transients at the level of the supratemporal plane. Furthermore, REA during dichotic application of CV syllables seems to be linked to functional dissociation of the two hemispheres during auditory processing.
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Affiliation(s)
- K Mathiak
- Department Neurology, University of Tübingen, Tübingen, Germany.
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41
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Kawakami O, Kaneoke Y, Kakigi R. Perception of apparent motion is related to the neural activity in the human extrastriate cortex as measured by magnetoencephalography. Neurosci Lett 2000; 285:135-8. [PMID: 10793245 DOI: 10.1016/s0304-3940(00)01050-8] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
To determine the neural correlate of apparent motion perception, we measured magnetic responses to visual stimuli in apparent motion and compared the results with subjective rating of the quality of perceived motion with varied stimulus timing. The latency of the magnetic response was about 150 ms, and its origin was estimated to be in the occipito-parieto-temporal junction. The strength of the first component in the response varied with the stimulus timing, the maximum value being at the interval 0. The change could not be explained by the simple summation of onset and offset responses and this value was related to the subjective rating of quality (smoothness) of motion measured of the stimulus. Results indicate there is a localized cortical region of neural activity which is closely related to the subjective assessment of quality of perceived motion.
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Affiliation(s)
- O Kawakami
- Department of Integrative Physiology, National Institute for Physiological Sciences, Myodaiji-Cho, Okazaki, Japan
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42
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He S, Norgren M. Magnetostatic image current and its application to an analytic identification of a current dipole inside a conducting sphere. IEEE Trans Biomed Eng 2000; 47:183-91. [PMID: 10721625 DOI: 10.1109/10.821753] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
The image solution for the static magnetic field outside a conducting sphere with an internal current dipole is considered. The image current, which is a linear distribution of magnetic dipoles on the line segment between the dipole point and the center of the sphere, is derived by using the fact that the induced current does not have any contribution to the radial component of the magnetic field outside the sphere. The image is then used to obtain some explicit formulas for identifying the location and tangential moment of the primary current dipole. This explicit identification method is also tested with a real model for a patient's brain.
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Affiliation(s)
- S He
- State Key Laboratory of Modern Optical Instrumentation, Zhejiang University, Hangzhou, China
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43
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Bundo M, Kaneoke Y, Inao S, Yoshida J, Nakamura A, Kakigi R. Human visual motion areas determined individually by magnetoencephalography and 3D magnetic resonance imaging. Hum Brain Mapp 2000. [DOI: 10.1002/1097-0193(200009)11:1<33::aid-hbm30>3.0.co;2-c] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
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44
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Alberstone CD, Skirboll SL, Benzel EC, Sanders JA, Hart BL, Baldwin NG, Tessman CL, Davis JT, Lee RR. Magnetic source imaging and brain surgery: presurgical and intraoperative planning in 26 patients. J Neurosurg 2000; 92:79-90. [PMID: 10616086 DOI: 10.3171/jns.2000.92.1.0079] [Citation(s) in RCA: 67] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
OBJECT The availability of large-array biomagnetometers has led to advances in magnetoencephalography that permit scientists and clinicians to map selected brain functions onto magnetic resonance images. This merging of technologies is termed magnetic source (MS) imaging. The present study was undertaken to assess the role of MS imaging for the guidance of presurgical planning and intraoperative neurosurgical technique used in patients with intracranial mass lesions. METHODS Twenty-six patients with intracranial mass lesions underwent a medical evaluation consisting of MS imaging, a clinical history, a neurological examination, and assessment with the Karnofsky Performance Scale. Magnetic source imaging was used to locate the somatosensory cortex in 25 patients, the visual cortex in six, and the auditory cortex in four. The distance between the lesion and the functional cortex was determined for each patient. Twenty-one patients underwent a neurosurgical procedure. As a surgical adjunct, a frameless stereotactic navigational system was used in 17 cases and a standard stereotactic apparatus in four cases. Because of the results of their MS imaging examination, two patients were not offered surgery, four underwent a stereotactic biopsy procedure, 10 were treated with a subtotal surgical resection, and seven were treated with complete surgical resection. One patient deteriorated before a procedure could be scheduled and, therefore, was not offered surgery, and two patients were offered surgery but declined. Three patients experienced surgery-related complications. CONCLUSIONS Magnetic source imaging is an important noninvasive neurodiagnostic tool that provides critical information regarding the spatial relationship of a brain lesion to functional cortex. By providing this information, MS imaging facilitates a minimum-risk management strategy and helps guide operative neurosurgical technique in patients with intracranial mass lesions.
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Affiliation(s)
- C D Alberstone
- Department of Radiology, University of New Mexico School of Medicine, Albuquerque 87131-5341, USA
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Ackermann H, Lutzenberger W, Hertrich I. Hemispheric lateralization of the neural encoding of temporal speech features: a whole-head magnetencephalography study. BRAIN RESEARCH. COGNITIVE BRAIN RESEARCH 1999; 7:511-8. [PMID: 10076097 DOI: 10.1016/s0926-6410(98)00054-8] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Using a passive oddball design (randomized series of standard [frequent] and deviant [rare] stimuli), the present study investigated the neural encoding of syllables differing in a duration parameter (/da/ = short-lag voice onset time [VOT], /ta/ = long-lag VOT) by means of whole-head magnetencephalography (MEG). Dipolar activities at the level of the supratemporal planes allowed to explain the evoked magnetic fields. The N1m/P2m-complex (magnetic equivalent to the N /P2-wave of the electroencephalogram) in response to standard stimuli showed bilateral symmetric distribution. Furthermore, the latency of P2m significantly depended on VOT. Finally, the mismatch response to the deviant /da/-syllables-which represent in German a very frequent word (English: 'here' or 'there')- evolved significantly earlier in the left hemisphere as compared to the right side. In conclusion, processing speed may be an important aspect of the hemispheric specialization of language.
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Affiliation(s)
- H Ackermann
- Department of Neurology, University of Tübingen, Germany.
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46
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Schack B, Grieszbach G, Nowak H, Krause W. The sensitivity of instantaneous coherence for considering elementary comparison processing. Part II: Similarities and differences between EEG and MEG coherences. Int J Psychophysiol 1999; 31:241-59. [PMID: 10076776 DOI: 10.1016/s0167-8760(98)00053-1] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The EEG (electroencephalogram) coherence depends on EEG deviation type. A high level of sensitivity of instantaneous coherence for investigating elementary cognitive tasks could be shown in the case of unipolar reference (ear lobe reference). In order to validate of this result the same investigations were performed for MEG (magnetoencephalogram) coherence, where EEG and MEG were measured simultaneously. A strong correlation between time intervals with high EEG and MEG coherence could be shown. The equivalence of the sensitivity of EEG and MEG coherence for the description of the dynamic behaviour of information processing and the distinction between different elementary cognitive tasks is proven statistically.
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Affiliation(s)
- B Schack
- Institute of Medical Statistics, Computer Science and Documentation, University of Jena, Germany.
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47
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Dynamic brain imaging: Event-related optical signal (EROS) measures of the time course and localization of cognitive-related activity. Psychon Bull Rev 1998. [DOI: 10.3758/bf03208834] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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Liu AK, Belliveau JW, Dale AM. Spatiotemporal imaging of human brain activity using functional MRI constrained magnetoencephalography data: Monte Carlo simulations. Proc Natl Acad Sci U S A 1998; 95:8945-50. [PMID: 9671784 PMCID: PMC21182 DOI: 10.1073/pnas.95.15.8945] [Citation(s) in RCA: 305] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
The goal of our research is to develop an experimental and analytical framework for spatiotemporal imaging of human brain function. Preliminary studies suggest that noninvasive spatiotemporal maps of cerebral activity can be produced by combining the high spatial resolution (millimeters) of functional MRI (fMRI) with the high temporal resolution (milliseconds) of electroencephalography (EEG) and magnetoencephalography (MEG). Although MEG and EEG are sensitive to millisecond changes in mental activity, the ability to resolve source localization and timing is limited by the ill-posed "inverse" problem. We conducted Monte Carlo simulations to evaluate the use of MRI constraints in a linear estimation inverse procedure, where fMRI weighting, cortical location and orientation, and sensor noise statistics were realistically incorporated. An error metric was computed to quantify the effects of fMRI invisible ("missing") sources, "extra" fMRI sources, and cortical orientation errors. Our simulation results demonstrate that prior anatomical and functional information from MRI can be used to regularize the EEG/MEG inverse problem, giving an improved solution with high spatial and temporal resolution. An fMRI weighting of approximately 90% was determined to provide the best compromise between separation of activity from correctly localized sources and minimization of error caused by missing sources. The accuracy of the estimate was relatively independent of the number and extent of the sources, allowing for incorporation of physiologically realistic multiple distributed sources. This linear estimation method provides an operator-independent approach for combining information from fMRI, MEG, and EEG and represents a significant advance over traditional dipole modeling.
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Affiliation(s)
- A K Liu
- Massachusetts General Hospital NMR Center, Building 149, Room 2301, 13th Street, Charlestown, MA 02129, USA
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Cohen LG, Ziemann U, Chen R, Classen J, Hallett M, Gerloff C, Butefisch C. Studies of neuroplasticity with transcranial magnetic stimulation. J Clin Neurophysiol 1998; 15:305-24. [PMID: 9736465 DOI: 10.1097/00004691-199807000-00003] [Citation(s) in RCA: 102] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
In recent years, there has been increasing interest in studies of brain plasticity. Although still loosely defined, this term describes the ability of the brain to change. Cortical plasticity encompasses a wide variety of phenomena and mechanisms, including modifications in cortical properties such as strength of internal connections, representational patterns, or neuronal modifications, either morphological or functional (Donoghue et al., 1996). We focus on the description of different ways in which transcranial magnetic stimulation (TMS) can be used to study patterns of reorganization and some of the mechanisms involved in these changes. Correlation between TMS and neuroimaging studies in humans and animal studies addressing similar questions is discussed. It is important to identify in each situation whether plasticity plays a beneficial role or is maladaptive in terms of functional compensation. The understanding of patterns, mechanisms, and functional relevance of cortical plasticity will hopefully lead to the design of effective strategies to enhance plasticity when it is beneficial and to down-regulate it when it is maladaptive. An example of a possible strategy, using TMS, is discussed.
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Affiliation(s)
- L G Cohen
- Human Cortical Physiology Unit, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland 20892, USA
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50
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Halgren E, Marinkovic K, Chauvel P. Generators of the late cognitive potentials in auditory and visual oddball tasks. ELECTROENCEPHALOGRAPHY AND CLINICAL NEUROPHYSIOLOGY 1998; 106:156-64. [PMID: 9741777 DOI: 10.1016/s0013-4694(97)00119-3] [Citation(s) in RCA: 431] [Impact Index Per Article: 16.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Recordings directly within the brain can establish local evoked potential generation without the ambiguities always associated with extracranial electromagnetic measures. Depth recordings have found that sensory stimuli activate primary cortex and then material-specific encoders. Sensory-specific areas remain active for long periods, but by about 200 ms are joined by activation in widespread brain systems. One system is related to the orientation of attention. It is centered in paralimbic and attentional frontoparietocingular cortex, and associated with the P3a. A second system associated with P3b envelopes cognitive contextual integration. It engages the ventral temporofrontal event-encoding cortices (inferotemporal, perirhinal, and ventrolateral prefrontal), association cortices (superior temporal sulcal and posterior parietal), and the hippocampus. Thus, even in simple tasks, activation is widespread but concentrated in particular multilobar systems. With this information, the late cognitive potentials can be used to monitor the probable location, timing and intensity of brain activation during cognitive tasks.
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Affiliation(s)
- E Halgren
- Department of Radiology, University of Utah, Salt Lake City 84108, USA.
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