Knowledge Base

Variables

In this section you find details and examples of the statistics you can use for your condition. For more information on a dependent variable, see the EthoVision XT Help.

Note: Dependent variables of Live Mouse Tracker and the social variables Train and Side by side are not available in the Trial Control Settings.

Distance Moved

Frequently-Used Statistics

• Current (default). To base your condition on the distance between the previous sample and the current one. This value depends on the chosen sample rate. Use Current velocity instead.
• Total. To base your condition on the distance traveled from the moment the condition becomes active up to that point.
• Mean. To base your condition on the average distance traveled from one sample to the next calculated from the activation of the condition box up to that time. This depends on the sample rate. Use Mean velocity instead.

Notes

• Effect of hidden zones. When the animal is in a hidden zone, the distance moved for the first sample in the hidden zone is based on the distance between the last location where the animal was detected and the center of the hidden zone. This is typically a relatively large distance, which can result in the condition becoming true.
• Effect of outliers (reflections). Detection of reflections may result in a too large distance moved and hence the condition being met.

Velocity

In the Condition window, click the Settings button. Choose the body point on which calculation of velocity is based, and the Averaging interval. For details, see Velocity in the EthoVision XT Help.

Frequently-Used Statistics

• Current (default). For a condition that is met when the velocity at the current sample is <=/>= a specified value.
• Total. This does not have a physical meaning and depends on the sample rate. Choose Mean instead.
• Mean. For a condition that is met when the mean velocity since the activation of the condition is <=/>= a specified value.

Notes

• Effect of hidden zones. When the animal is in a hidden zone, the velocity for the first sample in the hidden zone is based on the distance between the last location where the animal was detected and the center of the hidden zone. This is typically a relatively large velocity, which can result in the condition becoming true.
• Effect of jitter. When the animal moves slowly, jitter plays a bigger role than at higher speeds. This can make velocity exceed the threshold set in the condition.
• Effect of outliers (reflections). Detection of reflections may result in a too high velocity and hence the condition being met. To prevent this from happening, increase the Averaging interval in the settings.

Movement

In the Condition window, click the Settings button. In the Movement tab, specify which threshold values of velocity specify the states Moving and Not moving. Optionally, choose an Averaging interval to smooth out random changes in velocity that do not reflect real movement.

Frequently-Used Statistics

• Current. For a condition that is met when the animal's current state is either true (Moving) or false (Not moving).
• Frequency (default). For a condition that is met when the animal has moved/not moved a number of times.
• Cumulative duration. For a condition that is met when the animal has moved/not moved for a specific time since the activation of the condition.

  Example: A Movement condition is defined to stop tracking after 10 minutes of movement. If the animal moves during the first 2 minutes, stops moving for 3 minutes, and then moves again without interruption, the track is stopped 13 minutes after the start.

• Current duration. For a condition that is met when the animal has moved/not moved continuously for a specific time. In the same example as above, the condition would be: stop tracking when the current duration of movement is 10 minutes. Tracking would stop when the animal had moved continuously for 10 minutes, that is 15 minutes after the start.
• Latency to first. For details, see the Latency to First section.

Acceleration

In the Condition window, click the Settings button and choose the options you require.

Frequently-Used Statistics

• Current (default). To base your condition on the current value of acceleration.
• Total. To base your condition on the total acceleration from the moment the condition becomes active up to that point. Note that this value does not have a physical meaning and depends on the sample rate. Choose Mean instead.
• Mean. To base your condition on the average acceleration. The average is calculated from the activation of the condition box up to that time.

Note: Acceleration state is not available as a condition criterion. However, you can create a Multi condition that includes for example a condition "Acceleration > 10 cm/s for more than 1 second". This corresponds to a state variable based on Acceleration.

In Zone

In the Condition window, click the Settings button. Under In the following zones, select the zones of your choice. Under From following body points, select the body points of the animal that determine whether or not the animal is considered to be within a zone. Under Threshold, enter a Zone exit threshold to avoid that small movement of the body points across zone borders result in unrealistic scores of zone entries. Such movements are usually caused by body-point jitter, or the behavior of the subject (stretching, curling, etc.).

Frequently-Used Statistics

• Current. To base your condition on the presence of the animal in a zone at that time: either true (In zone) or false (Not in zone).
• Frequency (default). To base your condition on the number of times the animal has been in the zone.

  Important: The frequency of In zone becomes high very easily when the animal walks along the edge of a zone. This may result in the condition being met sooner than expected. If this happens, increase the Zone exit threshold. If that does not help, open the Detection settings and click Advanced, then under Smoothing set Track noise reduction to On. This smooths the track during acquisition, which means that the track is altered and cannot be reversed afterwards.

• Cumulative duration. To base your condition on the cumulative duration the animal has been in the zone up to that time since the activation of the condition.

  Example: In a Novel Object Recognition test, stop tracking when the animal has been in the zone for a specified cumulative duration.

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