Presentation of electromagnetic multichannel data: The signal space separation method

Taulu, Samu; Kajola, M.

doi:10.1063/1.1935742

Cited by 332 publications

(340 citation statements)

References 30 publications

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“…More recent investigations showed very similar tendencies. Van der Hiele et al (2007) found negative correlations between theta power and tests of global domain. In addition, negative correlations with tests such as the TMTB or semantic fluency were described by the authors.…”

Section: Discussionmentioning

confidence: 98%

MEG spectral analysis in subtypes of mild cognitive impairment

López

Cuesta

Garcés

et al. 2014

AGE

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Mild cognitive impairment (MCI) has been described as an intermediate stage between normal aging and dementia. Previous studies characterized the alterations of brain oscillatory activity at this stage, but little is known about the differences between single and multidomain amnestic MCI patients. In order to study the patterns of oscillatory magnetic activity in amnestic MCI subtypes, a total of 105 subjects underwent an eyes-closed resting-state magnetoencephalographic recording: 36 healthy controls, 33 amnestic single domain MCIs (a-sd-MCI), and 36 amnestic multidomain MCIs (a-md-MCI). Relative power values were calculated and AGE (2014) compared among groups. Subsequently, relative power values were correlated with neuropsychological tests scores and hippocampal volumes. Both MCI groups showed an increase in relative power in lower frequency bands (delta and theta frequency ranges) and a decrease in power values in higher frequency bands (alpha and beta frequency ranges), as compared with the control group. More importantly, clear differences emerged from the comparison between the two amnestic MCI subtypes. The a-md-MCI group showed a significant power increase within delta and theta ranges and reduced relative power within alpha and beta ranges. Such pattern correlated with the neuropsychological performance, indicating that the a-md-MCI subtype is associated not only with a "slowing" of the spectrum but also with a poorer cognitive status. These results suggest that a-md-MCI patients are characterized by a brain activity profile that is closer to that observed in Alzheimer disease. Therefore, it might be hypothesized that the likelihood of conversion to dementia would be higher within this subtype.

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Section: Discussionmentioning

confidence: 98%

MEG spectral analysis in subtypes of mild cognitive impairment

López

Cuesta

Garcés

et al. 2014

AGE

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“…The temporal signal space separation (tSSS) and head movement compensation aligning the data to the mean head position were used first (Elekta MaxFilter 2.2) to suppress noise from outside of the MEG dewar and to compensate for effects related to infants' head movement during the recording. This procedure was designed to improve the signal-to-noise ratio of the data by suppressing external interference (i.e., noise from outside of the helmet) without introducing excessive reconstruction noise (50,51). The infant head movement was evaluated by assessing the maximum SD of the center head position across all time points.…”

Section: Resultsmentioning

confidence: 99%

Musical intervention enhances infants’ neural processing of temporal structure in music and speech

Zhao

Kuhl

2016

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

153

104

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Individuals with music training in early childhood show enhanced processing of musical sounds, an effect that generalizes to speech processing. However, the conclusions drawn from previous studies are limited due to the possible confounds of predisposition and other factors affecting musicians and nonmusicians. We used a randomized design to test the effects of a laboratory-controlled music intervention on young infants' neural processing of music and speech. Nine-month-old infants were randomly assigned to music (intervention) or play (control) activities for 12 sessions. The intervention targeted temporal structure learning using triple meter in music (e.g., waltz), which is difficult for infants, and it incorporated key characteristics of typical infant music classes to maximize learning (e.g., multimodal, social, and repetitive experiences). Controls had similar multimodal, social, repetitive play, but without music. Upon completion, infants' neural processing of temporal structure was tested in both music (tones in triple meter) and speech (foreign syllable structure). Infants' neural processing was quantified by the mismatch response (MMR) measured with a traditional oddball paradigm using magnetoencephalography (MEG). The intervention group exhibited significantly larger MMRs in response to music temporal structure violations in both auditory and prefrontal cortical regions. Identical results were obtained for temporal structure changes in speech. The intervention thus enhanced temporal structure processing not only in music, but also in speech, at 9 mo of age. We argue that the intervention enhanced infants' ability to extract temporal structure information and to predict future events in time, a skill affecting both music and speech processing.M usic training in early childhood has received increased attention as a model for the study of functional neural plasticity (1). Previous studies investigating musically trained adults and children have demonstrated their enhanced processing of musical pitch and meter in comparison with nontrained groups (2-6). Moreover, prior evidence also suggests generalization effects from early musical training to speech processing. For example, musically trained adults and children can better process pitch information in lexical tones and temporal information in syllable structure, compared with nonmusicians (7-10). These cross-domain effects from early music training to speech perception raise theoretically interesting and important questions about different levels of processing (e.g., lower level acoustic processing vs. higher level cognitive skills) affected by early experience (11).However, there are several methodological issues preventing strong causal inferences about the effects of early music training in studies comparing musicians with nonmusicians. First, predispositions (e.g., higher auditory acuity) may lead individuals to self-select early music training, thus contributing to the observed differences between musicians and nonmusicians. Second, there exists gre...

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“…External noise was removed from the MEG data using the temporal extension of Signal-Space Separation (tSSS) (Taulu and Kajola 2005) as implemented with the MaxFilter software (version 2.2, Elekta-Neuromag) with a 10-s raw data buffer and a subspace correlation limit of 0.9. Data was subsequently adjusted for head movement every 200 ms and transformed into a common space.…”

Section: Meg Recordings and Preprocessingmentioning

confidence: 99%

Synchronization during an internally directed cognitive state in healthy aging and mild cognitive impairment: a MEG study

López

Garcés

Cuesta

et al. 2014

AGE

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Mild cognitive impairment (MCI) is a stage between healthy aging and dementia. It is known that in this condition the connectivity patterns are altered in the resting state and during cognitive tasks, where an extra effort seems to be necessary to overcome cognitive decline. We aimed to determine the functional connectivity AGE (2014) pattern required to deal with an internally directed cognitive state (IDICS) in healthy aging and MCI. This task differs from the most commonly employed ones in neurophysiology, since inhibition from external stimuli is needed, allowing the study of this control mechanism. To this end, magnetoencephalographic (MEG) signals were acquired from 32 healthy individuals and 38 MCI patients, both in resting state and while performing a subtraction task of two levels of difficulty. Functional connectivity was assessed with phase locking value (PLV) in five frequency bands. Compared to controls, MCIs showed higher PLV values in delta, theta, and gamma bands and an opposite pattern in alpha, beta, and gamma bands in resting state. These changes were associated with poorer neuropsychological performance. During the task, this group exhibited a hypersynchronization in delta, theta, beta, and gamma bands, which was also related to a lower cognitive performance, suggesting an abnormal functioning in this group. Contrary to controls, MCIs presented a lack of synchronization in the alpha band which may denote an inhibition deficit. Additionally, the magnitude of connectivity changes rose with the task difficulty in controls but not in MCIs, in line with the compensation-related utilization of neural circuits hypothesis (CRUNCH) model.

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Presentation of electromagnetic multichannel data: The signal space separation method

Cited by 332 publications

References 30 publications

MEG spectral analysis in subtypes of mild cognitive impairment

MEG spectral analysis in subtypes of mild cognitive impairment

Musical intervention enhances infants’ neural processing of temporal structure in music and speech

Synchronization during an internally directed cognitive state in healthy aging and mild cognitive impairment: a MEG study

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