Knowledge Base

The Start-Stop Trial Rule

The Start-Stop trial rule is displayed on your screen when you create or open Trial Control Settings. With this rule, you control the start and stop of data acquisition.

The Default Start-Stop Trial Rule

The default Start-Stop trial rule is a sequence of six boxes:

• Rule Begin - Start-Stop Trial. Activated when you start the trial (from the Acquisition menu, select Start Trial, or click the Start Trial button, or press Ctrl+F5). Once you start the trial, control passes to the next box.
• Condition - In Zone - Cumulative Duration >= 1 s. This is the default Start track condition. It is fulfilled when the center point of the subject (or of any subjects, in the case of an arena with multiple subjects) has been detected in the arena for 1 second after you started the trial. If you start the trial and the animal is not detected yet, the program waits until it detects the animal for 1 second, then it starts tracking.
• Action - Start Track. Activated when the condition on its left side is met. Once this box is activated, data recording (tracking) starts. If the condition placed between the Start-Stop trial box and this box is not met immediately, tracking starts later than the time you start the trial.
• Condition - Time - Infinite Time (condition never met). This is the default Stop track condition. This condition is never met. The trial stops when you give the Stop command or the time exceeds the maximum trial duration (when this has been set).
• Action - Stop Track. Marks the end of all tracks (and trial).
• Rule End - Start-Stop Trial. This box is just the delimiter of the rule; it does not take any action.

Important: Always keep a Condition box that determines when the track is stopped right before the Stop track Action box, otherwise the trial stops immediately after you start the trial.

The Start-Stop Trial Rule in Special Cases

• Multiple Arenas. When working with multiple arenas, the rule is applied separately for each arena. This means that tracking can start at different times in different arenas in the same trial, depending on when the condition placed immediately before the Start track box is met in a specific arena.
• DanioVision and Activity Analysis. If you selected Activity analysis in the Experiment Settings, or created a DanioVision experiment, there is no box between the Start-Stop trial and the Start track box. This means that tracking starts immediately when you click the Start Trial button. For more information on Activity analysis, see Activity analysis in the EthoVision XT Help, or the DanioVision DVOC-0041 - Reference Manual.
• Behavior Recognition. If you selected Behavior recognition in the Experiment Settings, the default Trial Control rule contains a Time condition box set to 3 seconds. This means that tracking starts 3 seconds after starting the trial. This is done because the Behavior recognition algorithm needs 3 seconds of video images to make the first classification of behavior. With this condition you make sure that your track contains Behavior recognition data since the first sample.

If you selected both Activity analysis and Behavior recognition in the Experiment Settings, the Trial Control Rule is the same as when you selected Behavior recognition only. For more information on Behavior recognition, see Behavior recognition in the EthoVision XT Help.

An Important Distinction: Trial vs. Track

• Trial. A trial can be viewed as a container for the data collected in one recording session. It starts when you give the Start command in acquisition and stops when the tracks for all arenas and subjects have stopped.
• Track. A track corresponds to the actual recording of a subject's position and behavior. The start of a track may or may not coincide with the start of the trial. This depends on your Trial Control Settings. If you use the default Trial Control Settings, the track starts 1 second after the animal has been detected in the arena and stops when you stop the trial.

A trial may contain one or more tracks. For example, if you track two subjects simultaneously, each trial includes two tracks, one per subject. Similarly, if your setup contains four arenas with two subjects each, each trial includes 4 arenas x 2 subjects = 8 tracks.

In a multiple-arena setup, the end of a track does not necessarily mean the end of the trial. The trial ends when all tracks come to an end.

Customize the Start-Stop Trial Rule

Although you can customize your Start-Stop trial rule in a number of ways, you cannot delete the following boxes: Rule Begin, Rule End, Action - Start track, and Action - Stop track.

Modify the Start Track Condition

The default Start track condition is an In Zone condition.

• To modify that condition, click the Settings button. In the window that appears, click Settings and specify the zone in which the animal should or should not be in order for the program to start tracking.
• To use another condition (for example: start recording exactly 1 minute after starting the trial), delete first the current condition (click that box and press Delete) and insert the new one.
• To start recording as soon as you start the trial, delete the Start track condition. Click the box immediately before the Start track box and press Delete.

Modify the Stop Track Condition

The default Stop track condition is a Time condition.

• To modify that condition, click the Settings button and choose the option you require.
• To use another condition, delete first the current condition (click that box and press Delete) and insert the new one.

Important: Keep at least one condition between Start track and Stop track. If you do not do this, tracking stops immediately after tracking starts, resulting in no data.

Important: If you have inserted Condition boxes based on Activity in your Trial Control rule and then deselect Activity analysis in the Experiment Settings, the Condition boxes based on Activity are removed from your sequence.

Source: EthoVision XT 18 - THC - Trial and Hardware Control, Noldus Information Technology