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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

Maps of the source strength that is needed to obtain a detection probability of 0.7 in one participant [from Hillebrand and Barnes (47)]. Data were recorded with a 151 MEG scanner with third order gradiometer configuration. The folded cortical surface is viewed from the right (A), left-midline (B), and top (C). The colormap of the source strength is clipped at 10 nAm. For a detection probability of 70% reasonable source strength is sufficient to detect signals from most areas of the brain. For deep sources, a source strength of at least 10 nAm is needed in order to obtain a high detection probability. Figure adapted from Hillebrand and Barnes (47).
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Figure 6: Maps of the source strength that is needed to obtain a detection probability of 0.7 in one participant [from Hillebrand and Barnes (47)]. Data were recorded with a 151 MEG scanner with third order gradiometer configuration. The folded cortical surface is viewed from the right (A), left-midline (B), and top (C). The colormap of the source strength is clipped at 10 nAm. For a detection probability of 70% reasonable source strength is sufficient to detect signals from most areas of the brain. For deep sources, a source strength of at least 10 nAm is needed in order to obtain a high detection probability. Figure adapted from Hillebrand and Barnes (47).

Mentions: Based on the estimation by Hillebrand and Barnes (47), for MEG the probability of detecting a source as deep as the amygdala can be as low as 10% (Figure 2). Hillebrand and Barnes (47) also estimated the strength of magnetic field required to detect sources with a probability of 70% for all regions of the brain (see Figure 6). From this, it can be seen that recording from sub-cortical structures requires stronger responses compared to cortical sources by at least four orders of magnitude. More recently, Goldenholz et al. (45) confirmed this assertion and also found that the SNR of EEG was low in the inferior frontal areas, possibly due to inadequate sampling of the scalp potential distribution with the low electrode array they used (n = 70).


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

Adjamian P - Front Neurol (2014)

Maps of the source strength that is needed to obtain a detection probability of 0.7 in one participant [from Hillebrand and Barnes (47)]. Data were recorded with a 151 MEG scanner with third order gradiometer configuration. The folded cortical surface is viewed from the right (A), left-midline (B), and top (C). The colormap of the source strength is clipped at 10 nAm. For a detection probability of 70% reasonable source strength is sufficient to detect signals from most areas of the brain. For deep sources, a source strength of at least 10 nAm is needed in order to obtain a high detection probability. Figure adapted from Hillebrand and Barnes (47).
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 6: Maps of the source strength that is needed to obtain a detection probability of 0.7 in one participant [from Hillebrand and Barnes (47)]. Data were recorded with a 151 MEG scanner with third order gradiometer configuration. The folded cortical surface is viewed from the right (A), left-midline (B), and top (C). The colormap of the source strength is clipped at 10 nAm. For a detection probability of 70% reasonable source strength is sufficient to detect signals from most areas of the brain. For deep sources, a source strength of at least 10 nAm is needed in order to obtain a high detection probability. Figure adapted from Hillebrand and Barnes (47).
Mentions: Based on the estimation by Hillebrand and Barnes (47), for MEG the probability of detecting a source as deep as the amygdala can be as low as 10% (Figure 2). Hillebrand and Barnes (47) also estimated the strength of magnetic field required to detect sources with a probability of 70% for all regions of the brain (see Figure 6). From this, it can be seen that recording from sub-cortical structures requires stronger responses compared to cortical sources by at least four orders of magnitude. More recently, Goldenholz et al. (45) confirmed this assertion and also found that the SNR of EEG was low in the inferior frontal areas, possibly due to inadequate sampling of the scalp potential distribution with the low electrode array they used (n = 70).

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