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The application of electro- and magneto-encephalography in tinnitus research - methods and interpretations.

Adjamian P - Front Neurol (2014)

Bottom Line: Some of the neural changes associated with tinnitus may be assessed non-invasively in human beings with MEG and EEG (M/EEG) in ways, which are superior to animal studies and other non-invasive imaging techniques.I also discuss some pertinent methodological issues involved in tinnitus-related studies and conclude with suggestions to minimize possible discrepancies between results.The overall message is that while MEG and EEG are extremely useful techniques, the interpretation of results from tinnitus studies requires much caution given the individual variability in oscillatory activity and the limits of these techniques.

View Article: PubMed Central - PubMed

Affiliation: MRC Institute of Hearing Research , Nottingham , UK.

ABSTRACT
In recent years, there has been a significant increase in the use of electroencephalography (EEG) and magnetoencephalography (MEG) to investigate changes in oscillatory brain activity associated with tinnitus with many conflicting results. Current view of the underlying mechanism of tinnitus is that it results from changes in brain activity in various structures of the brain as a consequence of sensory deprivation. This in turn gives rise to increased spontaneous activity and/or synchrony in the auditory centers but also involves modulation from non-auditory processes from structures of the limbic and paralimbic system. Some of the neural changes associated with tinnitus may be assessed non-invasively in human beings with MEG and EEG (M/EEG) in ways, which are superior to animal studies and other non-invasive imaging techniques. However, both MEG and EEG have their limitations and research results can be misinterpreted without appropriate consideration of these limitations. In this article, I intend to provide a brief review of these techniques, describe what the recorded signals reflect in terms of the underlying neural activity, and their strengths and limitations. I also discuss some pertinent methodological issues involved in tinnitus-related studies and conclude with suggestions to minimize possible discrepancies between results. The overall message is that while MEG and EEG are extremely useful techniques, the interpretation of results from tinnitus studies requires much caution given the individual variability in oscillatory activity and the limits of these techniques.

No MeSH data available.


Related in: MedlinePlus

Different types of cross-frequency coupling. The interaction between brain regions can be assessed by measuring transient synchronization between the recorded activities. (A) Slow-wave activity in the theta band (8 Hz) with fluctuation power (red line) but stable frequency. Gamma frequency oscillation (B-G) can interact with this signal in the following ways: (B) amplitude in the gamma oscillation can correlate with that of the theta band irrespective of changes in phase of the two signal; (C) phase-locking between two signals occurs as one oscillation period of signal A corresponds to three periods of signal C, which remains locked or fixed; (D) modulations in the amplitude of the gamma oscillation are correlated to the phase of the slow-wave activity; (E) modulations in the frequency of gamma oscillation is correlated with the phase of A; (F) frequency modulations in the fast gamma activity is coupled to the amplitude of modulations in the slow-wave theta activity; (G) changes in one frequency range are induced by changes in another frequency range. Adapted from Jirsa and Müller (181).
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Figure 7: Different types of cross-frequency coupling. The interaction between brain regions can be assessed by measuring transient synchronization between the recorded activities. (A) Slow-wave activity in the theta band (8 Hz) with fluctuation power (red line) but stable frequency. Gamma frequency oscillation (B-G) can interact with this signal in the following ways: (B) amplitude in the gamma oscillation can correlate with that of the theta band irrespective of changes in phase of the two signal; (C) phase-locking between two signals occurs as one oscillation period of signal A corresponds to three periods of signal C, which remains locked or fixed; (D) modulations in the amplitude of the gamma oscillation are correlated to the phase of the slow-wave activity; (E) modulations in the frequency of gamma oscillation is correlated with the phase of A; (F) frequency modulations in the fast gamma activity is coupled to the amplitude of modulations in the slow-wave theta activity; (G) changes in one frequency range are induced by changes in another frequency range. Adapted from Jirsa and Müller (181).

Mentions: The most likely mechanism to facilitate functional connectivity between different regions is thought to be transient synchronization of neuronal oscillatory activity, which binds the activity from distributed neural ensembles into a coherent representation of cognitive and sensory functions (87). Perceptual binding and functional integration require large-scale neural synchrony and coordinated activity of distributed neural ensembles (179). The scope of this large-scale synchronization is neural assemblies which are >1 cm apart (87), such as, for example, assemblies across hemispheres or between auditory and pre-frontal cortices. Transient synchronization can be measured by various forms of coupling, using frequency, phase, and amplitude of the signal. Jensen and Colgin (180) and Jirsa and Müller (181) summarize the different principles of cross-frequency interdependencies between signals (see Figure 7), which include power to power, phase to phase, phase to frequency, and phase to power.


The application of electro- and magneto-encephalography in tinnitus research - methods and interpretations.

Adjamian P - Front Neurol (2014)

Different types of cross-frequency coupling. The interaction between brain regions can be assessed by measuring transient synchronization between the recorded activities. (A) Slow-wave activity in the theta band (8 Hz) with fluctuation power (red line) but stable frequency. Gamma frequency oscillation (B-G) can interact with this signal in the following ways: (B) amplitude in the gamma oscillation can correlate with that of the theta band irrespective of changes in phase of the two signal; (C) phase-locking between two signals occurs as one oscillation period of signal A corresponds to three periods of signal C, which remains locked or fixed; (D) modulations in the amplitude of the gamma oscillation are correlated to the phase of the slow-wave activity; (E) modulations in the frequency of gamma oscillation is correlated with the phase of A; (F) frequency modulations in the fast gamma activity is coupled to the amplitude of modulations in the slow-wave theta activity; (G) changes in one frequency range are induced by changes in another frequency range. Adapted from Jirsa and Müller (181).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4230045&req=5

Figure 7: Different types of cross-frequency coupling. The interaction between brain regions can be assessed by measuring transient synchronization between the recorded activities. (A) Slow-wave activity in the theta band (8 Hz) with fluctuation power (red line) but stable frequency. Gamma frequency oscillation (B-G) can interact with this signal in the following ways: (B) amplitude in the gamma oscillation can correlate with that of the theta band irrespective of changes in phase of the two signal; (C) phase-locking between two signals occurs as one oscillation period of signal A corresponds to three periods of signal C, which remains locked or fixed; (D) modulations in the amplitude of the gamma oscillation are correlated to the phase of the slow-wave activity; (E) modulations in the frequency of gamma oscillation is correlated with the phase of A; (F) frequency modulations in the fast gamma activity is coupled to the amplitude of modulations in the slow-wave theta activity; (G) changes in one frequency range are induced by changes in another frequency range. Adapted from Jirsa and Müller (181).
Mentions: The most likely mechanism to facilitate functional connectivity between different regions is thought to be transient synchronization of neuronal oscillatory activity, which binds the activity from distributed neural ensembles into a coherent representation of cognitive and sensory functions (87). Perceptual binding and functional integration require large-scale neural synchrony and coordinated activity of distributed neural ensembles (179). The scope of this large-scale synchronization is neural assemblies which are >1 cm apart (87), such as, for example, assemblies across hemispheres or between auditory and pre-frontal cortices. Transient synchronization can be measured by various forms of coupling, using frequency, phase, and amplitude of the signal. Jensen and Colgin (180) and Jirsa and Müller (181) summarize the different principles of cross-frequency interdependencies between signals (see Figure 7), which include power to power, phase to phase, phase to frequency, and phase to power.

Bottom Line: Some of the neural changes associated with tinnitus may be assessed non-invasively in human beings with MEG and EEG (M/EEG) in ways, which are superior to animal studies and other non-invasive imaging techniques.I also discuss some pertinent methodological issues involved in tinnitus-related studies and conclude with suggestions to minimize possible discrepancies between results.The overall message is that while MEG and EEG are extremely useful techniques, the interpretation of results from tinnitus studies requires much caution given the individual variability in oscillatory activity and the limits of these techniques.

View Article: PubMed Central - PubMed

Affiliation: MRC Institute of Hearing Research , Nottingham , UK.

ABSTRACT
In recent years, there has been a significant increase in the use of electroencephalography (EEG) and magnetoencephalography (MEG) to investigate changes in oscillatory brain activity associated with tinnitus with many conflicting results. Current view of the underlying mechanism of tinnitus is that it results from changes in brain activity in various structures of the brain as a consequence of sensory deprivation. This in turn gives rise to increased spontaneous activity and/or synchrony in the auditory centers but also involves modulation from non-auditory processes from structures of the limbic and paralimbic system. Some of the neural changes associated with tinnitus may be assessed non-invasively in human beings with MEG and EEG (M/EEG) in ways, which are superior to animal studies and other non-invasive imaging techniques. However, both MEG and EEG have their limitations and research results can be misinterpreted without appropriate consideration of these limitations. In this article, I intend to provide a brief review of these techniques, describe what the recorded signals reflect in terms of the underlying neural activity, and their strengths and limitations. I also discuss some pertinent methodological issues involved in tinnitus-related studies and conclude with suggestions to minimize possible discrepancies between results. The overall message is that while MEG and EEG are extremely useful techniques, the interpretation of results from tinnitus studies requires much caution given the individual variability in oscillatory activity and the limits of these techniques.

No MeSH data available.


Related in: MedlinePlus