# Head directed to zone

Definition

A discrete (state event) variable that is scored when the subject’s head is directed towards a zone or a circular area around a point. See Define zones and Draw a point

note Head directed to zone is not available if your experiment is set to:

▪Center-point detection.

▪Color marker tracking.

▪Live Mouse Tracker.

▪Center-point, nose-point and tail-base detection, with two subjects per arena tracked with Deep learning.

Calculation

1.The Head direction line is calculated. See Head direction

2.If the Head direction line crosses the zone of interest (or a circular area around a point), the value of Head directed to zone for that sample is set to 1. The samples with 1 are used to calculate the duration of Head directed to zone.

The figure below shows Head directed to zone in the exported data file (Analysis > Export > Raw Data). Two samples are highlighted, one when the head is directed to the zone (circle), the other when it is not.

How to specify Head directed to zone

1.Click the Add button next to Head directed to zone.

2.In the Head directed to zone tab, under Zone of interest select a Zone or a Point. For the latter, you can select either a point you defined in the Arena Settings or the center of a zone.

Because a point has an infinitely small surface area, you need to define a circular zone around the point. The default radius is 0.1 cm. The smaller the radius around a point, the less likely it is that the animal's head is exactly directed at this point.

3.Next, you can specify when Head directed to zone should be calculated, depending on the location of the animal:

▪Calculate when: From this list you select the body point that should be in the zone selected in the In list. If you select All detected body points, Head directed to zone is only calculated when all three body points are in the zone selected in the In list.

▪In: Select one of the zones from this list.

4.Complete the procedure to add the variable. See Calculate statistics: procedure.

Notes

▪Head directed to zone is based on the Head direction variable, which in turn depends on which method is used to track the nose-point. See Head direction

▪Head directed to zone is not available if your experiment is set to Only center-point detection or Color marker tracking.

▪If you swap the nose-point and the tail-base point in the Track Editor, the Head direction line is updated, and it is calculated as the prolongation of the segment joining the nose-point and the center-point. Head directed to zone is calculated based on the new angle.

▪If you edit the position of the nose-point or the center-point in the Track Editor, the value of Head directed to zone does not change.

Applications

Head directed to zone is especially designed for use in the Novel object test. Exploration of a novel object is normally defined as directly attending to the object when the head is within a 2 cm radius of the object (Ennaceur and Delacour (1988) Behavioural Brain Research, 31, 47-59). In EthoVision XT, you calculate Head directed to zone when the Nose-point of the animal is within a 2 cm radius from the center of the zone you have drawn around the novel object.