Limits...
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.


The difference between evoked and induced M/EEG responses. The AEF on the left is the linear average of many short trials whose responses are phase-locked to the onset of a stimulus. For induced responses (middle traces), linear averaging will remove the effect of interest due to variable phase relationship between trials. The information within induced responses is obtained by evaluating the frequency spectrum of each trial (right panels) over time, which is then averaged. The frequency information of individual trials is thus retained (bottom right panel).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4230045&req=5

Figure 5: The difference between evoked and induced M/EEG responses. The AEF on the left is the linear average of many short trials whose responses are phase-locked to the onset of a stimulus. For induced responses (middle traces), linear averaging will remove the effect of interest due to variable phase relationship between trials. The information within induced responses is obtained by evaluating the frequency spectrum of each trial (right panels) over time, which is then averaged. The frequency information of individual trials is thus retained (bottom right panel).

Mentions: Evoked responses appear after the onset of a stimulus and are phase- and time-locked to it, meaning that the signal of interest has a fixed time-delay to the stimulus. In general, event-related potentials are considered as the response of a stationary system to the external stimulus due to synchronous changes in afferent activity of neurons. Evoked power can be extracted by a simple linear method, such as the averaging of many trials to enhance signal-to-noise-ratio so that the noise is averaged out and the evoked response becomes apparent (Figure 5).


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

Adjamian P - Front Neurol (2014)

The difference between evoked and induced M/EEG responses. The AEF on the left is the linear average of many short trials whose responses are phase-locked to the onset of a stimulus. For induced responses (middle traces), linear averaging will remove the effect of interest due to variable phase relationship between trials. The information within induced responses is obtained by evaluating the frequency spectrum of each trial (right panels) over time, which is then averaged. The frequency information of individual trials is thus retained (bottom right panel).
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 5: The difference between evoked and induced M/EEG responses. The AEF on the left is the linear average of many short trials whose responses are phase-locked to the onset of a stimulus. For induced responses (middle traces), linear averaging will remove the effect of interest due to variable phase relationship between trials. The information within induced responses is obtained by evaluating the frequency spectrum of each trial (right panels) over time, which is then averaged. The frequency information of individual trials is thus retained (bottom right panel).
Mentions: Evoked responses appear after the onset of a stimulus and are phase- and time-locked to it, meaning that the signal of interest has a fixed time-delay to the stimulus. In general, event-related potentials are considered as the response of a stationary system to the external stimulus due to synchronous changes in afferent activity of neurons. Evoked power can be extracted by a simple linear method, such as the averaging of many trials to enhance signal-to-noise-ratio so that the noise is averaged out and the evoked response becomes apparent (Figure 5).

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.