5.2. “Power by sections” Mode

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