Knowledge Base

Definition

The shortest distance between a subject's body point (or selection of points) and a zone (or group of zones). You can calculate the distance regardless of where the body point is, or assuming that the point is always outside the zone (in the latter case, the distance is set to zero when the body point enters the zone).

The calculation of this variable is performed in two steps:

1. The coordinates of the point on the zone border that is closest to the coordinates of the body point for the current sample are found.
2. The distance in a straight line between the two coordinates is calculated.

How to Specify Distance to Zone

1. Click the Add button next to Distance to zone and click the Distance to zone tab.
2. Under To the following zones, select the zones you want to consider for the calculation. For example, if you want to calculate the mean distance to Zone 1, select Zone 1. By default, Arena is selected.

   If you have chosen two or more zones, select how the zones should be analyzed:

   • For each of the selected zones. Zones are analyzed separately.
   • Shortest distance to any zone. For each sample, EthoVision XT chooses the zone that is currently closest to the point(s) you have chosen, and uses the resulting distances for calculating the statistics.
3. Select the Include if in zone option if you want to calculate the distance to the border of a zone of interest, regardless of whether the subject is outside or inside the zone. If you want to calculate the distance to the border of the zone when the subject is outside the zone, leave this option cleared. See one of the Notes below.
4. Under From following body points, select the points you want to consider for the calculation. For example, select Nose-point if you want to analyze the distance between the nose-point and a specific zone. By default, Center-point is selected.

   If you have chosen two or more body points, select one of the following from the list:

   • For each selected point. Statistics are calculated for each point separately.
   • Shortest distance to any point. For each sample, EthoVision XT chooses the body point that is currently closest to the zone, and uses the resulting distances for calculating the statistics.
5. Complete the procedure to add the variable. See Calculate statistics: procedure.

Notes

• If you have selected Include if in zone in the Distance to zone tab of the variable's properties window, and the body point's coordinates lie inside the zone, the Distance to zone is greater than 0.

  Example: Effect of the option Include if in zone on the distance to zone (DZ, dotted lines) for three consecutive samples 1, 2 and 3. The zone is shown in gray. When the option is not selected, and sample 3 is within the zone, DZ for that sample is zero. When the option is selected, DZ for sample 3 has a value larger than zero.

• If your experiment is set to Only center-point detection or Color marker tracking, the body point options are not available. Calculations are based on the center point.

Application

Two examples of how you can use Distance to zone with Include if in zone not selected:

• In a Morris water maze test with the hidden platform defined as a zone, Distance to zone can measure the animal's progress towards the platform. You can select the Total statistic to give a measure of the cumulative distance to zone (for training trials) and the Mean statistic to give a measure of average proximity (for probe trials; Gallagher et al. 1993. Behav. Neurosci.: 618–626). See also the chapter The Morris water maze test in the EthoVision XT 19 Application Manual for the exact procedure. You can also divide the maze into quadrants to give a more fine-grained analysis of behavior during the trial.
• In a study of territorial behavior, the resident's territory could be defined as a zone. You can then measure how close the intruder comes to that area.

One example of how you can use Distance to zone with Include if in zone selected:

• In a study of anxiety, one could define an entire open field as a zone, and then use Distance to zone to measure to what extent animals dare to move away from the wall. More generally, if you are interested in the distance between a subject and the edge of an open field or the border of an Elevated plus maze, you can select the complete arena as a zone.

Definition

The shortest distance between a subject's body point and one or more points. The calculation of this variable is performed in two steps:

1. The coordinates of the defined point(s) and the body point(s) for the current sample are found.
2. The distance in a straight line between the coordinates is calculated.

If your experiment is set to Only center-point detection or Color marker tracking, the body point options are not available. Calculations are based on the center point.

How to Specify Distance to Point

1. Click the Add button next to Distance to point and click the Distance to point tab.
2. Under To following points, select the points you want to consider for the calculation. For example, if you want to calculate the mean distance to Cue 1, select Cue 1. By default, Arena (that is, the center of the Arena) is selected.

   If you have chosen two or more points, select how the points should be analyzed:

   • For each of the selected points: Points are analyzed separately.
   • Shortest distance to any points: For each sample, EthoVision XT chooses the point that is currently closest to the body point(s) you have chosen, and uses the resulting distances for calculating the statistics.
3. Under From following body points, select the points you want to consider for the calculation. For example, select Nose-point if you want to analyze the distance between the nose-point and a specific point. By default, Center-point is selected.

   If you have chosen two or more body points, select one of the following from the list:

   • For each of the selected points: Statistics are calculated for each point separately.
   • Shortest distance to any point: For each sample, EthoVision XT chooses the body point that is currently closest to the point, and uses the resulting distances for calculating the statistics.
4. Complete the procedure to add the variable. See Calculate statistics: procedure.

Notes

• If your experiment is set to Only center-point detection or Color marker tracking, the body point options are not available. Calculations are based on the center point.
• The center point of a zone can lie outside the zone itself. This occurs when the zone is ring-shaped or very asymmetrical.

Applications

Below are two examples of how Distance to point is of particular use in studies of spatial orientation:

• When analyzing the flight behavior of an insect in an odor plume, the plume itself can be defined as a zone, while the upwind odor source is regarded as a point. Using Distance to point, you can measure the insect's progress towards the source at any moment in time.
• In an open field test, using the center point of the central area of the arena, Distance to point can be used to measure how far the animal ventured into the central area.

Source: EthoVision XT 19 Help, Noldus Information Technology