Documentation

5.2. “Power by sections” Mode

Updated 31 August 20262 min read

5.2.1. Controls

Power by sections mode controls with numbered callouts for Trim (1), CAR (2), Denoise (3), frequency band selector (4), aggregation method (5), Relative toggle (6), epoch length (7), play button (8) and output-type selector (9), above the resulting power-by-section data table.

  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

Power by sections results table with numbered callouts marking the section/filter row labels (1), the per-channel power value columns for F8, AF4, AF3, F7 and zygoma electrodes (2), the epoch length setting (3), and the section visibility checklist (4).

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