Peak-to-Peak (PtP)

Peak-to-Peak (PtP)#

Peak-to-peak (PtP) amplitude is max(signal) - min(signal) over the analyzed interval. It emphasizes transient excursions and outlier bursts.

For execution steps, see Tutorial.

Subject-report PtP views#

View

Encoding

What it reveals

Channel-wise topomap (3D)

one PtP value per channel in sensor space

spatial pattern of excursion burden

Channel-wise distribution

one PtP value per channel

outlier channels and heavy-tail behavior

Channel × epoch heatmap

PtP per channel and epoch

when/where transient bursts occur

1) Channel-wise PtP topomap (3D)#

PtP topomap

Interpretation:

  • focal extremes indicate spatially localized transients,

  • broad elevation suggests global bursts or movement-related effects.

2) Channel-wise PtP distribution#

PtP distribution

Interpretation:

  • long upper tail indicates burst-prone channels,

  • multi-modal distributions can indicate mixed channel populations.

3) Channel × epoch heatmap#

PtP heatmap

Interpretation:

  • vertical hot stripes: time-localized global excursions,

  • horizontal hot stripes: channel-specific recurrent burst behavior,

  • top/right profiles summarize epoch- and channel-level burden.

PtP (manual) vs PtP (auto)#

  • PtP (manual): MEGqc’s internal PtP pathway and thresholds.

  • PtP (auto): MNE-based automatic PtP pathway (when present).

Both can appear as separate tabs in subject reports. Compare them when validating threshold behavior.

QC implications#

  • persistent high-PtP channels are bad-channel candidates,

  • sparse high-PtP epochs can be rejected selectively,

  • combine with STD/PSD to avoid rejecting physiologically plausible high-amplitude signal.

The same visualization patterns apply to both MAG and GRAD channel types. PtP (auto) uses MNE’s built-in detection algorithm, while PtP (manual) uses MEGqc’s custom thresholding approach.