Signal-space projections of MEG data characterize both distributed and well-localized neuronal sources

Tesche, C. D.; Uusitalo, Mikko A.; Ilmoniemi, Risto J.; Huotilainen, Minna; Kajola, M.; Salonen, Oili

doi:10.1016/0013-4694(95)00064-6

Cited by 324 publications

(212 citation statements)

References 17 publications

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“…Adjacent parts of the cortex either do not contribute to the surface-recorded MEG-signal (crown of the pre-and the postcentral gyrus) or cause a reversed pattern of magnetic fields due to opposite orientation of the cortical layers (posterior bank of the precentral sulcus and the central sulcus). These results taken together with earlier observations on the mu-rhythm (see above) and recent MEG studies on oscillatory activity by MEG [33] suggest that MI is active with internal simulation of movements.…”

Section: Discussionsupporting

confidence: 85%

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Electric and magnetic fields of the brain accompanying internal simulation of movement

Lang¹,

Cheyne

Höllinger³

et al. 1996

Cognitive Brain Research

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Methods of functional brain imaging have been used to identify brain structures which are active during internal simulation of movements (ISM). Between 1977 and 1993 it was consistently reported that the primary motor cortex (MI) is not active during ISM whereas other cortical areas, in particular the supplementary motor area (SMA) are active. ISM was assumed to be a situation of 'internal programming'. Brain systems involved in ISM or 'programming' were hypothesized to be superior to and separable from 'executive system' including MI. We have studied electric and magnetic fields of the brain when subjects internally simulated either a single movement or a sequence of movements. Results of the studies are consistent with the assumption that MI is active with ISM. Internally subjects experienced effort which was required to inhibit overt movements during ISM. A recent EEG study showed different patterns of cortical activity with ISM and with movement inhibition suggesting that different brain structures may be active during ISM and movement inhibition [23].

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Section: Discussionsupporting

confidence: 85%

“…Oscillatory spontaneous activity of about 10 Hz has recently been detected in multi-channel MEG recordings and located in the rolandic area when subjects internally simulated a karate routine [32,33].…”

Section: Oftmentioning

confidence: 99%

Electric and magnetic fields of the brain accompanying internal simulation of movement

Lang¹,

Cheyne

Höllinger³

et al. 1996

Cognitive Brain Research

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“…For ASSR analysis, the grand-averaged magnetic field signals within the time range from 0.5 to 1 s were used for single equivalent current dipole estimations (43), and the maximal source strength for each condition and hemisphere was calculated by using the source space projection technique (44). For the N1m analysis, the grand-averaged magnetic fields were 30 Hz low-pass filtered and baseline corrected (31,32,45).…”

Section: Methodsmentioning

confidence: 99%

Listening to tailor-made notched music reduces tinnitus loudness and tinnitus-related auditory cortex activity

Okamoto¹,

Stracke²,

Stoll

et al. 2009

Proc. Natl. Acad. Sci. U.S.A.

232

206

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Maladaptive auditory cortex reorganization may contribute to the generation and maintenance of tinnitus. Because cortical organization can be modified by behavioral training, we attempted to reduce tinnitus loudness by exposing chronic tinnitus patients to self-chosen, enjoyable music, which was modified ("notched") to contain no energy in the frequency range surrounding the individual tinnitus frequency. After 12 months of regular listening, the target patient group (n = 8) showed significantly reduced subjective tinnitus loudness and concomitantly exhibited reduced evoked activity in auditory cortex areas corresponding to the tinnitus frequency compared to patients who had received an analogous placebo notched music treatment (n = 8). These findings indicate that tinnitus loudness can be significantly diminished by an enjoyable, low-cost, customtailored notched music treatment, potentially via reversing maladaptive auditory cortex reorganization.cortical plasticity | human auditory cortex | lateral inhibition | magnetoencephalography | MEG S ubjective tinnitus (1) is among the most prevalent symptoms of hearing disorders in industrialized countries (2, 3). Tinnitus loudness can be considered as the most tangible tinnitus characteristic. In 1-3% of the general population, the tinnitus sensation is loud enough to affect the quality of life (4). Causal treatment strategies for tinnitus are not yet available.The lack of treatment strategies is due to incomplete knowledge concerning the mechanisms of tinnitus generation and maintenance. However, recent neurophysiological studies have shown that tinnitus is presumably caused by maladaptive auditory cortex reorganization (4-6) (similar phenomena were observed also in somatosensory cortex; refs. 7-9). For instance, magnetoencephalography (MEG) studies have demonstrated that auditory cortical map areas corresponding to the tinnitus frequency were distorted; the amount of distortion correlated positively with perceived tinnitus strength (10). Moreover, auditory cortex activity corresponding to the tinnitus frequency was shown to be enhanced and related to perceived tinnitus intrusiveness (11).To date, widely used tinnitus treatment strategies (e.g., tinnitus retraining therapy; ref. 12) are merely symptom management approaches. Therefore, there is a great demand for causal treatment approaches targeting the tinnitus percept more directly. Recent neurophysiological studies indicate that behavioral training can be a powerful means to reverse maladaptive cortical reorganization (7, 13).A previous study (14) demonstrated that listening to spectrally "notched" music can reduce cortical activity corresponding to the notch center frequency, possibly through lateral inhibition. Motivated by this finding, we developed an innovative tinnitus treatment strategy aimed at reducing tinnitus loudness. The treatment regimen consists of regular listening to enjoyable, custom-tailored notched music. Here, we evaluate and report results of the treatment from a longitudinal double-blinded ...

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“…Given the relatively small amplitude of even the SSR it is perhaps not surprising that some of the studies have produced different results. In the present study using MEG data from a whole head array we have elected to unite a complex wavelet based time-frequency decomposition with the method of source space projection (SSP), (sometimes called signal space or subspace projection , Ilmoniemi et al, 1987, Tesche et al, 1995, and "Lead Field Synthesis", by Robinson, 1989. The use of these methods produces a significant improvement in signal-to-noise ratio in both amplitude and phase measures.…”

Section: Introductionmentioning

confidence: 99%

Cortical source estimates of gamma band amplitude and phase are different in schizophrenia

et al. 2008

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Reductions in gamma band phase synchrony and evoked power have been reported in schizophrenic subjects in response to auditory stimuli. These results have been observed in the EEG at one or two electrode sites. We wished to extend these results using magnetic field data to estimate the responses at the neural generators themselves in each hemisphere. Whole head magnetoencephalographic (MEG) recordings were used to estimate the phase and amplitude behavior of sources in primary auditory cortex in both hemispheres of schizophrenic and comparison subjects. Both ipsi-and contralateral cases were evaluated using a driving (40 Hz modulated 1 kHz carrier) and a non-driving (1 kHz tone) stimulus. We used source space projection (SSP) to collapse the magnetic field data into estimates of the time course of source strengths in individual trials. Complex wavelet based timefrequency decomposition was used to compute inter-trial phase locking factor (PLF), and mean evoked and induced amplitude for each cortical generator. Schizophrenic subjects showed reduced SSP PLF and evoked source strength for contra-lateral generators responding to the driving stimulus in both hemispheres. For the pure tone stimulus, only the left hemisphere PLF's in the transient window were reduced. In contrast, subjects with schizophrenia exhibited higher induced 40 Hz power to both stimulus types, consistent with the reduced PLF findings. The method of SSP combined with wavelet based complex demodulation produces a significant improvement in signal-to-noise ratio, and directly estimates the activity of the cortical generators responsible for gamma band auditory MEG evoked fields. Schizophrenic subjects exhibit significant impairment of generation and phase locking of this activity in auditory cortex, suggesting an impairment of GABA-ergic inhibitory interneuronal modulation of pyramidal cell activity.

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Signal-space projections of MEG data characterize both distributed and well-localized neuronal sources

Cited by 324 publications

References 17 publications

Electric and magnetic fields of the brain accompanying internal simulation of movement

Electric and magnetic fields of the brain accompanying internal simulation of movement

Listening to tailor-made notched music reduces tinnitus loudness and tinnitus-related auditory cortex activity

Cortical source estimates of gamma band amplitude and phase are different in schizophrenia

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