Event definitions for Fear Conditioning experiments

Fear conditioning experiments involve conditioned stimuli (CS) and unconditioned stimuli (US). This page extends the BIDS Events specification with the stricter event labels required by the Calibench Fear Conditioning challenge.

In the Calibench Fear Conditioning challenge, event labels distinguish between reinforced CS+ trials, unreinforced CS+ trials, CS- trials, delivered US events, omitted US events, and CS- matched US timepoints.

The events.tsv file MUST use the event labels defined below. These labels are part of the benchmark contract and are used by currently linked methods and importers.

Event labels

Table 1: Fear Conditioning event labels

Stimulus	Reinforced?	Naming	Description
CS+	yes	CSpr	A reinforced conditioned trial.
CS+	no	CSpu	An unreinforced conditioned trial.
CS-	no	CSm	The non-conditioned stimulus.
US		USp	The event in which an unconditioned stimulus, or threat, was present.
US		USo	The timepoint where the US would have appeared in an unreinforced CS+ trial.
US		USm	The event where the US would have appeared in CS- trials, helping avoid bias in the comparison.

Required M-BIDS columns

BIDS task events already define onset and duration. In addition to these BIDS columns, Calibench fear-conditioning events.tsv files MUST contain the following M-BIDS columns:

Table 2: Required additional events.tsv columns

Column	Description	Example
event_type	Fear Conditioning event label. The value must be one of CSpr, CSpu, CSm, USp, USo, or USm.	CSpr
task_name	Experimental phase represented by the row. Acquisition files can contain habituation and acquisition rows; extinction files contain extinction rows.	acquisition

Do not rename these columns. Additional columns may be included when available, but the importer expects the required columns and event labels listed here.

Optional columns

Calibench datasets may include the following optional columns. They are useful for interpretation and richer metadata, but they are not required by the Calibench fear-conditioning importer.

Table 3: Optional events.tsv columns

Column	Description	Example
stimulus_name	Stimulus identifier. If present, use values documented in the sidecar levels.	square, diamond, shock
HED	Hierarchical Event Descriptor tags for the event.	Sensory-event,Visual-presentation

Task entities and phases

Calibench fear-conditioning files use the BIDS task entities task-acquisition and task-extinction.

task-acquisition files may include rows whose task_name is habituation before the acquisition trials. task-extinction files use task_name value extinction.

When stimulus_name is present, use dataset-specific values documented in the event sidecar. Common Calibench values include:

Table 4: Stimulus names

Value	Description
square	Geometric CS+ stimulus.
diamond	Geometric CS- stimulus.
shock	Electrical unconditioned stimulus.

Example events.tsv

An example task-acquisition events.tsv file with optional stimulus_name and HED columns looks like this:

onset       duration        event_type      stimulus_name   HED     task_name
10.0        8.0     CSpu    square  Sensory-event,Visual-presentation,Experimental-condition/CS-plus,Experimental-condition/Unreinforced    habituation
17.5        0.0     USo     square  Experimental-condition/CS-plus,Experimental-condition/Unreinforced,Experimental-condition/Expectation-violation habituation
41.5        8.0     CSm     diamond Sensory-event,Visual-presentation,Experimental-condition/CS-minus       habituation
49.0        0.0     USm     diamond Experimental-condition/CS-minus,Experimental-condition/Expectation-violation,Somatosensory-stimulation  habituation
134.4995    8.0     CSpr    square  Sensory-event,Visual-presentation,Experimental-condition/CS-plus,Experimental-condition/Reinforced      acquisition
141.99950000000013  0.4253501000348478      USp     shock   Sensory-event,Somatosensory-stimulation,Aversive-stimulus       acquisition

Interpretation notes

CSpr and CSpu both refer to CS+ trials, but they distinguish whether the trial was reinforced or unreinforced.

USp marks a delivered unconditioned stimulus.

USo marks the omitted US timepoint in an unreinforced CS+ trial.

USm marks the matched timepoint where a US would have appeared during a CS- trial. This allows methods to compare responses at equivalent timepoints and helps avoid bias in the benchmark comparison.