Knowledge Base

Variables (Continued)

Arm of a T maze five times (Frequency=5).

Important: The frequency of Zone transition can become high very easily when the animal walks along the boundary between zones. This may result in the condition being met sooner than expected. If that happens, increase the Zone exit threshold. If this does not help, open the Detection settings and click Advanced, then under Smoothing set Track noise reduction to On. This smooths the track.

Latency to First.

Example: Take an action when the latency of the first transition from Zone A to Zone B is longer than 1 minute.

Heading

Use Heading for a condition based on compass-like orientation, provided that the axis orientation in the Arena Settings has some biological meaning.

In the Condition window, click the Settings button. In the Body points tab, select the body point that you want to use to calculate heading.

Frequently-Used Statistics

• Current (default). To base your condition on the current heading value.
• Mean. To base your condition on the mean value since the activation of the condition.

Heading to Point

In the Condition window, click the Settings button. Under Select, select the point (or zone center) that your condition is based on. Under For the following body points, select the body point for which heading is calculated.

Frequently-Used Statistics

• Current (default). To base your condition on the current meander value.
• Mean. To base your condition on the mean value since the activation of the condition.

Example: Take an action when the animal's Heading to the Entry zone is less than 5 degrees. Select Current as Statistic, <= 5°. Click Settings and specify Entry zone (center).

To restrict the condition to when the animal is moving, create a condition based on Movement, and combine the two conditions with an operator of type All.

Note: Heading is about movement. If you want to create a condition based on the animal's head orientation, use Head directed to zone (see below).

Head Direction

Use Head direction for a condition based on compass-like orientation. Since Head direction depends on the orientation of the axes in the Arena Settings, Head direction makes sense if the axis orientation has biological significance.

If the animal must point to a zone or point, use Head directed to zone.

Frequently-Used Statistics

• Current (default). To base your condition on the current value of head direction.
• Mean. To base your condition on the average head direction angle up to that time.

We advise you to specify a range of Head direction, using two conditions (one specifying >=, the other <=). Then, combine the conditions with an operator of type All.

Example: If the x axis points to North, then to make a condition that is met when Head direction is between NE and NW, combine:

• A condition that states Current Head direction <= +90°.
• A condition that states Current Head direction >= -90°.

Head Directed to Zone

In the Condition window, click the Settings button. Under Zone of interest, select the zone or point that your condition is based on. Under Calculate when, specify to calculate the variable only when the animal (or one of its body points) is in a specific zone.

We advise you to define a zone around the focal zone/point, so the variable is calculated only when the animal is near the focal zone.

Frequently-Used Statistics

• Frequency (default). To base your condition on the number of times the animal's head points to a zone (or point).
• Current. To base your condition on whether the animal's head points to a zone (or point).

Example: Take an action when the animal's head is directed to the novel object.

By selecting Current, the condition will become true as soon as the animal's head points to a zone for an instant. If you want to make the condition become true when the animal's head points to a zone for some time, use Current duration instead.

• Cumulative Duration. To base your condition on the cumulative time that the animal points to a zone or point since the activation of the condition.
• Current Duration. To base your condition on the time that the animal's head has been pointing to the zone without interruption up to the current time.

Example: Take an action when the animal's head is directed to the novel object for five seconds.

Latency to First. See Figure 24 for reference.

Turn Angle

In the Condition window, click the Settings button. In the Turn Angle tab, specify whether the turn is Absolute (unsigned) or Relative (signed). Select whether you want to calculate the Head direction turn angle (body points will be ignored). In the Body points tab, select the body point that you want to use to calculate Turn angle.

Frequently-Used Statistics

• Current (default). To base your condition on the current value.
• Total. To base your condition on the cumulative value (whether absolute or relative) since the activation of the condition.
• Mean. To base your condition on the mean value (whether absolute or relative) since the activation of the condition.

Angular Velocity

In the Condition window, click the Settings button. In the Angular velocity tab, specify whether the turn is Absolute (unsigned) or Relative (signed). Select whether you want to calculate the Head direction angular velocity (body points will be ignored). In the Body points tab, select the body point that you want to use to calculate Angular velocity.

Frequently-Used Statistics

See Turn Angle above.

Activity

With Activity you can create a condition based on the change in pixels in the whole arena (thus not only in the detected body area) between samples. When properly set, this pixel change is supposed to be a measure for the subject's activity (for example, it is low when the subject freezes).

Frequently-Used Statistics

• Current. The percentage pixel change in the arena relative to the previous sample.
• Total. The total percentage pixel change in the arena, from the moment the box becomes active onwards.
• Mean. The mean percentage pixel change in the arena, from the moment the box becomes active onwards.

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