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5.2. “Power by sections” Mode

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Table of Contents

5.2.1. Controls #

  1. Trim: Remove artifact segments
  2. CAR: Common average reference
  3. Denoise: Blink artifact suppression
  4. Filter: Frequency filter selection
  5. Function: Aggregation function (sum, mean, median, std)
  6. Relative: Relative values (percentage of the total spectrum)
  7. Epoch length: Epoch length for averaging
  8. Recalculation button
  9. Mode selection: Power by sections / Between-channel interactions

5.2.2. Results Table #

    The table contains: #

    1. Section/filter: Section name or filter name
    2. F8, AF4, AF3, F7, L Zygoma: Power for each electrode
    3. Epoch length: Epoch length
    4. Power: Checkbox for including or excluding the section

    5.2.3. Power Calculation Method #

    • Transformations are applied: Trim, CAR, Denoise (blink artifacts)
    • The frequency filter is applied (if selected)
    • The signal is converted to power:
      power = signal.^2
    • Epoch averaging is applied:
      power_smoothed = filtfilt(moving_average, 1, power)
    • An aggregate statistic is calculated for each section:
      sum: sum(power_section) / Fs (power integral)
      mean: mean(power_section) (mean power)
      median: median(power_section) (median power)
      std: std(power_section) (standard deviation)

    5.2.4. Relative Values #

    When Relative is enabled:

    • Total power (without filtering) is calculated for each channel.
    • Power in the selected band is expressed as a percentage:
      relative_power = 100 * filtered_power / total_power

    Interpretation: Percentage of power in the selected frequency band relative to the total signal power.

    Physiological explanation of relative power:

    Absolute power depends on many factors (contact quality, individual characteristics). Relative power shows what share of total brain activity belongs to a given frequency band.

    • Relative power is more stable and makes it easier to compare people.
    • It shows the “balance” between different rhythms.

    Examples:

    • Alpha 50%: half of the brain’s activity is alpha rhythm (strong relaxation)
    • Beta 30%: one third of the activity is beta rhythm (active thinking)
    • Theta 10%: one tenth of the activity is theta rhythm (light sleep or meditation)

    Interpretation of changes:

    • Increased relative alpha: transition toward relaxation
    • Increased relative beta: transition toward active work
    • A change in balance reflects a change in functional state