Knowledge Base

Problem

A user wants to track and analyze when an LED or light stimulus turns on or off during a trial and correlate this with behavioral changes (e.g., locomotor activity changes). They need a workflow to detect and time-stamp light state changes automatically within EthoVision.

Details

Symptom: No built-in EthoVision parameter directly reports external light on/off state. Users need a workaround to detect light state changes using the camera feed. Affected: EthoVision XT any version with Activity Analysis capability. Use case: Optogenetics, fear conditioning, or any protocol where an LED or room light is part of the arena and its state changes are relevant.

Solution

1. Position the LED or light source so it is visible within the camera's field of view and within the arena image.
2. In Arena Settings, include the light/LED area as part of the arena (or define a specific zone covering the light).
3. In Detection Settings, use the Activity measure. Set the activity threshold to a high value (e.g., 100) so that only the dramatic pixel change caused by the light turning on or off is detected as 'activity,' not the animal's movement.
4. In the Analysis Profile, use a Free Interval with the start criterion set to 'Activity > [threshold]%' to mark the onset of the light event, and the stop criterion set to the activity falling below the threshold (light off).
5. This approach timestamps light on/off transitions as behavioral epochs that can be exported and analyzed.
6. Test the setup with a mock trial to confirm the activity threshold correctly captures only light state changes and not animal movement.
7. Contact Noldus Support for a backup experiment file demonstrating this configuration if needed.