OPM-MEG Active Oddball

PsychoPy script for an active auditory oddball paradigm in the Scully OPM-MEG facility. Based on the FieldTrip cued oddball paradigm.

Bimanual left/right index-finger responses, 3 blocks × 100 trials (~51 minutes), continuous EyeLink recording, VPIXX pixel-mode triggers, and hardware-scheduled VPIXX audio.

Trial structure

+-----------+-----+-----------------+---------+----------+-------+
| fixation  | cue | auditory stim   | resp.   | feedback | BLINK |
|  1500 ms  |500ms|  4000-8800 ms   | 1000 ms |  400 ms  | 500 ms|
|     +     | >+> | tones + oddball |    +    |  (errors |       |
|           | or  |                 |         |   only)  |       |
|           | <+< |                 |         |          |       |
+-----------+-----+-----------------+---------+----------+-------+

The subject sees an arrow cue directing them to prepare a left- or right-hand response, hears 3–7 standard tones (1000 Hz) followed by one deviant tone (1200 Hz), and presses the index-finger button on the cued hand as quickly as possible.

Files

• oddball_active_cued_ft_VPIXXaudio_KBDinput.py — main script
• EyeLinkCoreGraphicsPsychoPy.py — renders EyeLink calibration graphics inside PsychoPy
• *.wav — sound files used by EyeLink for calibration / target beeps

Requirements

Software:

• PsychoPy 2026.1+
• pypixxlib (VPIXX)
• pylink (SR Research)

For Windows setup, an installer script that installs PsychoPy and the required dependencies is available at ScullyCenter-Psychopy-Install-Win.

Hardware:

• VPixx DATAPixx3 + SOUNDPixx + PROPixx
• SR Research EyeLink
• HID-keyboard button box (e.g. Current Designs)

Running the script

Most common way: open the .py file in the PsychoPy Coder window and click Run.

Alternative for users with PsychoPy installed in a conda environment:

python oddball_active_cued_ft_VPIXXaudio_KBDinput.py

Either way, a startup dialog asks for participant ID, session number, and two dummy-mode checkboxes:

• dummy_eyelink — run without EyeLink Host PC. Auto-forced on if pylink isn't installed.
• dummy_vpixx — run without a DATAPixx3. Audio falls back to PsychoPy sound (audible but not vsync-locked), and *_vp / *_vp_est columns in the output CSVs are left blank. Auto-forced on if pypixxlib isn't installed.

A clean laptop with only PsychoPy installed can still run the paradigm end-to-end for demo or development purposes.

Pre-flight checklist

1. VPIXX device on and reachable (DPxOpen succeeds), or check dummy_vpixx
2. VPIXX running Pixel Mode B (the script enables it)
3. Audio wired to the desired path (headphones or loudspeakers) at audible volume
4. Button box emitting keyboard events; update KEY_CODES in the script to match your box
5. Button box TTL trigger output wired into the MEG trigger channel
6. EyeLink Host PC at 100.1.1.1, or check dummy_eyelink
7. Audio transit delay measured (microphone at earpiece); record for latency correction in analysis

Output files

Written to results/sub-<p>_ses-<s>_task-oddballftcued/:

• ..._trials.csv — one row per trial (main behavioral log)
• ..._tones.csv — one row per tone with per-tone VPIXX timestamps
• ..._presses.csv — one row per keyboard event (all presses, not just scored responses)
• ....EDF — EyeLink data downloaded from the Host PC at session end

CSVs are flushed at the end of every block, so a crash mid-run doesn't lose completed blocks.

Timestamp columns are suffixed by clock provenance:

• _pp — PsychoPy default clock (behavioral RT reference)
• _vp — VPIXX DATAPixx3 hardware clock (MEG alignment reference)
• _vp_est — Estimated VPIXX-clock time for events VPIXX didn't directly detect (keyboard presses). Accurate to within ~one video frame; use the button box's TTL wiring into the MEG trigger channel as the definitive response reference.

Technical details

The module docstring at the top of oddball_active_cued_ft_VPIXXaudio_KBDinput.py covers everything not in this README: audio scheduling and vsync locking, trigger scheme, trigger vs. perceived-stimulus timing corrections, keyboard input caveats, response scoring rules, and block structure. Read there for extending or debugging the script.