Stim Files -
Even experienced engineers encounter STIM file failures. Here is a troubleshooting checklist:
This section tells the system how to interpret the electrical signals coming from the sensor. It transforms raw voltage or resistance into meaningful physical units (like Celsius or Pascals). It contains:
While no universal standard exists, most stim files share a common row‑based, column‑delimited structure (e.g., tab‑separated or comma‑separated values). A representative example (visual search task): stim files
| trial | condition | target_orientation | distractor_orientation | set_size | onset_ms | duration_ms | img_file | |-------|-----------|--------------------|------------------------|----------|----------|-------------|-------------------| | 1 | target | 45 | 135 | 8 | 0 | 200 | gratings/45deg.bmp| | 2 | distractor | - | 90 | 8 | 2500 | 200 | gratings/90deg.bmp| | 3 | catch | - | - | 0 | 5000 | 200 | blank.bmp |
Common columns include:
Measured in microseconds (µs), pulse width dictates how long each individual electrical burst lasts. Shorter pulses tend to target larger nerve fibers (often related to paresthesia-based pain relief), while longer pulses may recruit smaller fibers. A stim file locks in this critical temporal variable.
In Digital Signal Processing (DSP), the stimulus is not a binary toggle but a continuous waveform represented by discrete samples. Even experienced engineers encounter STIM file failures
Deep Dive: The Sampler: In music production, a "Sampler" is an instrument explicitly designed to treat audio files as stimulus. It maps digital files to triggers (MIDI notes). The architecture of modern sampler engines (e.g., Kontakt, SFZ) involves complex scripting layers that determine how the stim file is played back—altering pitch, loop points, and envelope, effectively turning the stimulus file into a malleable instrument.
This is the mandatory section of the STIM file. It provides the "ID card" for the sensor. It includes: Deep Dive: The Sampler: In music production, a
A robust STIM file naming convention prevents lab disasters. Avoid final_protocol.stim. Instead use:
[Date]_[SubjectID]_[Region]_[Type]_[Amplitude]_[Freq].stim
Example: 20231027_SlackRat_VPL_Block_150uA_130Hz.stim