In zone
A discrete (state event) variable with two possible states, In zone and Not in zone, depending on whether the body point chosen is within a zone (or group of zones).
The state for a specified zone is determined for each sample by comparing the coordinates of the chosen body point with the coordinates that make up the zone of interest.
1.Click the Add button next to In zone and click the In zone tab in the window that appears.
2.Under In the following zones, select the zones you want to analyze. For example, if you want to calculate the total time the animal was in Zone 1, select Zone 1.
If you have chosen two or more zones, select how body points should be analyzed:
▪For each selected zone: The body points are analyzed in each zone separately.
▪When in any of the selected zones: The body points are analyzed when in any of the selected zones.
▪When in all selected zones: The body points are analyzed when in all those zones simultaneously.
▪When not in any of the zones: The body points are analyzed that are in none of the selected zones.
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 calculate the statistics of the time the nose point was in 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.
▪If any point is in zone: Statistics are calculated for when any of the selected points is in the zone.
▪When all points are in zone: Statistics are calculated for when all the selected points are in a zone simultaneously.
4.Under Threshold, enter the Zone exit threshold. That is, once the animal’s body point is detected in the zone, the animal is considered to be in the zone until its distance from the zone border (when outside the zone) exceeds that threshold. Default: 0 cm. Use this option to remove false re-entries resulting from random movements of the body point around the zone border. The following example shows the effect of the threshold for different trajectories. The frequency is shown for In zone.
5.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 In zone variable is calculated for the center-point.
▪To find a good Zone exit threshold for In zone, plot the values of Distance moved for the body point you are interested in. For instance, in a Novel object test, plot the distance moved for the nose-point while the subject explores an object, that is, while its nose-point is within the border of the zone “object”. Take note of the variation in the per-sample distance moved and set the Zone exit threshold higher than this range.
▪If two zones are adjacent, that is, not overlapping, the subject’s body point is supposed to be either in one or the other zone. However, when the zone exit threshold is greater than zero, the subject’s body point may not yet be outside zone 1, and (by definition) be already in zone 2. To prevent this, re-define the two zones in such a way there is a gap between the two, with its width at least the same as the threshold.
▪When you export In zone as raw data, the values are exported for each sample time, with possible values 0 (Not in zone), 1 (In zone), or “-” (unknown). See Export the raw data (track and dependent variables)
▪When a body point is missing for more than three consecutive samples, the In zone state ends and the remaining missing samples are not assigned to any state (neither In zone or Not in zone).
▪If you analyze the time that the subject spent in a zone that includes a hidden zone, the results are only given for when the subject is visible (and therefore detected) in the larger zone. If you want to calculate the total time in that zone including the time spent in the hidden zone, select both zones in the In zone settings (step 2 above), and sum up the time values for the two zones reported in the results table.
In zone is a standard variable for any study involving the usage of space by animals. For example:
▪Open field: How much time did the animal spend by the walls, and how long did it take to cross the open center? (for example, Berendsen et al. 1994, Behav. Pharm. 5 (Suppl. 1): 81).
▪Maze studies: How many errors did the animal make? (for example, Ploeger G.E. 1995, PhD thesis, Utrecht University) How long did it take to get to the target (Ploeger et al. 1994, Behav. Neurosci. 108, 927-934) How many times did the animal enter the open arms in a plus maze? (Law et al. 2003. J. Neurosci. 23: 10419-10432).
▪Four-way olfactometer: How much time did the animal spend in the treated odor field? When did it first enter one of the arms? (Kaiser and de Jong 1994, Behav. Proc. 30: 175-184).
▪Water-maze: How much time does the animal spend in an 18-cm wide path (Whishaw's corridor) from the starting location to the platform, designated as the correct route? If a rat deviated from this route, it received a maximum of one error on that trial (Whishaw's error, Whishaw 1985, Behav. Neurosci. 99(5): 979-1005), indicating that it did not show a direct swim path.