Knowledge Base

Follow

Definition

A discrete (state event) variable that is scored when the focal subject walks directly in the path of another subject.

Calculation

Follow along path is scored when the following conditions are met:

• Both subjects move at a speed higher than 5 pixels per frame.
• The two subjects are not in contact with any other subject.
• The angle between their direction vectors is smaller than 45°.
• The focal subject's center point lies within a rectangular area drawn based on the position of the followed subject. This is checked beginning from the current video frame time to the 15th frame before the current one. So the software checks that the focal subject enters the path up to 0.5 s after the followed subject has been there.
• The distance between the two subjects' center points is smaller than two mean body lengths. This mean body length is calculated using all values of distance nose-tail base of the followed (i.e., non focal) subject within the track.

How to Specify Follow

1. Open an Analysis profile and in the Dependent Variables panel, under Live Mouse Tracker, click the Add button next to Follow.
2. Complete the procedure to add the variable to the Analysis profile. See Calculate statistics: procedure.

Note

Follow looks similar to a train of two mice. However it depends on the definition of the train.

If subject A is following closely subject B, this is scored as A Follows B but also as a Train for subject A, when the distance between A and B is shorter than the threshold set in the Train settings, and when the train is defined as in the cases below:

• A > B.
• Actor > B.
• Actor > Any.

Note that:

• Follow is scored for the subject that follows another one. If subject A follows subject B, Follow is scored for subject A, not B.
• Train is scored for all the subjects involved in the train definition. So when subject A follows subject B, an instance of Train defined as A > B is scored for subject A and for subject B.

See Also

• Dependent variables for Live Mouse Tracker

Get Away

Definition

A discrete (state event) variable that is scored when the focal subject walks away from another subject.

Calculation

The variable Get away is scored when:

• The speed of the focal subject is greater than or equal to the speed of the other subject.
• The speed of the focal subject or the other subject is greater than the value set as threshold (5 cm/s). This threshold cannot be changed as it is hard-coded.
• The distance between the two subjects increases.

Note that if the other subject is sitting still, Get away is not scored for the focal subject, no matter what the latter does.

How to Specify Get Away

1. Open an Analysis profile and in the Dependent Variables panel, under Live Mouse Tracker, click the Add button next to Get away.
2. Click the Receivers tab. Under Select, choose the subjects that the focal subject moved away from. If you select two or more subjects, select one of the available options from the list:
   • All selected subjects: Get away is scored when the focal subject moved away from all the subjects selected above simultaneously.
   • Any selected subject: Get away is scored when the focal subject moved away from any of the subjects selected above.
   • Each subject: Get away is scored when the focal subject moved away from one of the subjects selected above. The results are displayed for each Receiver.
3. Complete the procedure to add the variable to the Analysis profile. See Calculate statistics: procedure.

Notes

• To calculate this variable, EthoVision XT checks the subject's speed at time t based on the change in the X,Y coordinates between t-1 and t+1, like in the original algorithm of Live Mouse Tracker. In EthoVision XT, the Velocity variable at time t is calculated based on the change in the X,Y coordinates between t-1 and t. See Velocity.

Example

Subject A is moving to the left, away from subjects B and D. Accordingly, the state events Get away are scored for the two combinations A-B and A-D. The duration of the state events depends on when the conditions listed above are valid for each combination. Because subject C is still, Get away is not scored for the combination A-C.

In the Trial Statistics results table, with the default layout, the results of Get away are shown per subject (on the rows). The columns vary depending on what you chose in the Receivers tab:

• If you chose Each subject, the columns contain the statistics of Get away from specific subjects (for example, From A to D).
• If you chose All selected subjects or Any selected subject, a column From all of A, B, C, D or From any of A, B, C, D contains cumulative statistics of Get away when the subject moved away from all the cage mates simultaneously or from any of them, respectively, depending on which option you chose.

See Also

• Dependent variables for Live Mouse Tracker

Group

Definition

A discrete (state event) variable that is scored when the focal subject is in contact with one or more subjects.

Calculation

EthoVision XT uses the events of type Contact stored in the Live Mouse Tracker database.

• Group size 2 is scored when the focal subject is in contact with only one subject. If the animal is in contact with more than one animal the event is not scored.
• Group size 3 is scored when the focal subject is in contact with only two other subjects to form a group of three animals.
• Group size 4 is scored when the focal subject is in contact with three other subjects to form a group of four animals.

EthoVision XT splits the results depending on who forms each group. For example, A can form groups of 2 subjects, resulting in groups AB, AC and AD. The overall results (AB+AC+AD) are also shown.

How to Specify Group

1. Open an Analysis profile and in the Dependent Variables panel, under Live Mouse Tracker, click the Add button next to Group.
2. Specify the Group size.
3. Complete the procedure to add the variable to the Analysis profile. See Calculate statistics: procedure.
4. If you wish to have the results for all group sizes in one table, repeat the steps above to add a total of three Group variables, one for each group size.

Applications

You can use the Group variable to quantify the tendency of subjects to form groups. For example, a mouse model of social deficit may show reduced time spent in groups.

See Also

• Dependent variables for Live Mouse Tracker

Source: EthoVision XT 19 Help, Noldus Information Technology