EEG Asymmetry Index
Compute epoch-paired ln(right power)−ln(left power) and its average; electrodes, band selection, referencing and artifact rejection are caller responsibilities.
Description
EEG log asymmetry compares paired right and left powers on a natural-log scale.
EEG log asymmetry compares paired right and left powers on a natural-log scale. The sign depends on which side is subtracted.
The tool returns epochLogAsymmetries (epoch log asymmetries); meanLogAsymmetry (mean log asymmetry). Input measurements and model parameters are supplied by the caller; the tool computes the stated summary rather than acquiring those measurements.
When to use EEG Asymmetry Index
Use EEG Asymmetry Index when you already have leftEpochPowers, rightEpochPowers and want epochLogAsymmetries, meanLogAsymmetry. This is useful for checking a supplied calculation, documenting a measurement convention, or comparing observations prepared on the same basis.
How to use EEG Asymmetry Index and understand its results
- Enter leftEpochPowers, rightEpochPowers using the field table below. Match the units, ordering and data boundaries described in the calculation.
- Run the tool after checking the stated bounds and matching paired observations or categories. A malformed request gives a tool error rather than a usable measurement.
- Read epochLogAsymmetries, meanLogAsymmetry. Use the calculation and interpretation below to distinguish amounts, ratios, signs and decision flags where applicable.
- Review the supplied parameters and assumptions before using the result in a report or comparing it with another observation.
| Input field | Meaning | Value type and bounds | Requirement |
|---|---|---|---|
| leftEpochPowers | Left epoch powers | list of number | Required |
| rightEpochPowers | Right epoch powers | list of number | Required |
Require positive aligned epoch powers. Return each log difference and its arithmetic mean; positive values indicate greater right power.
asymmetry = ln(rightPower)−ln(leftPower) The symbols refer to the supplied quantities or generated values described above; unit conversions and comparison boundaries follow the stated implementation.
{
"input": {
"leftEpochPowers": [
1,
4
],
"rightEpochPowers": [
2,
8
]
},
"output": {
"epochLogAsymmetries": [
0.6931471805599453,
0.6931471805599452
],
"meanLogAsymmetry": 0.6931471805599452
}
}Limitations and assumptions
Band selection, reference montage, artifact rejection and physiological interpretation are external.
Numerical inputs must be finite. The tool checks its declared input shape and calculation constraints; those checks do not verify the quality, calibration or representativeness of the supplied observations.
Alternative or Complementary methods
Spectral Edge Frequency: Locate a requested integrated PSD fraction by trapezoidal integration and within-bin linear-density inversion; not a percentile of frequency samples. EEG Microstate Duration: Measure target-state contiguous EEG label run durations and sample coverage; recording-edge partial runs are included and absence gives empty durations with zero coverage.
Methodological background: Measures of scale: sample variance and standard deviation.1
References
-
Measures of scale: sample variance and standard deviation — NIST/SEMATECH
Similar or alternative tools
- Spectral Edge Frequency
Locate a requested integrated PSD fraction by trapezoidal integration and within-bin linear-density inversion; not a percentile of frequency samples.
- EEG Microstate Duration
Measure target-state contiguous EEG label run durations and sample coverage; recording-edge partial runs are included and absence gives empty durations with zero coverage.