Handling slow drift

Problem. Slow drift dominates the recording, and trial rejection removes everything.

The pipeline

1. High Pass — l_freq 1 Hz for most work, 0.1 Hz if you need slow components.
2. Epoch — after the filter, never before.
3. Reject by Variance.

What to watch

The order matters more than the cutoff. Rejecting trials before removing drift means the variance you threshold on is mostly drift, which is what produces SS-E030.

A 1 Hz high pass distorts slow evoked components. If you are studying them, use 0.1 Hz and accept a longer filter.