Nesting over Movement

Aim

To pick out the data collected when the subject was in one of the movement states: Moving or Not moving.

example Calculate the average Head direction (an estimate of body orientation in fish) when the subject was Moving.

Nesting vs. Nesting over Subjects

Notice the difference when there are multiple subjects in the same arena:

▪To select data of a subject based on the Movement state of that subject, choose Movement under Nesting. See the procedure below.

▪To select data of a subject based on the Movement state of other subjects, choose Movement under Nesting over subjects. There you find the Actors tab where you can specify which subjects (Actors) were in a certain Movement state. See Nesting over subjects

Procedure

1.In the Data Profile, under Nesting click the button next to Movement.

2.In the Movement window:

▪Under Outlier filter, enter an Averaging interval to smooth the velocity values.

▪Under Threshold, enter the Start velocity and the Stop velocity that the states Not moving and Moving are based on.

▪Under Calculate nesting for, select the Movement state that defines the intervals.

note The default values are an example and may not apply to your experiment. The threshold values also vary between species. If the subject is very slow, like a walking tick, you must reduce the two thresholds to detect true movement. See also Dependent Variables in Detail > Movement.

3.Click the Body Points tab (when available), and specify the body points that Movement is based on. Choose whether Movement is based on all the chosen points moving simultaneously (All selected points) or not (Any selected point).

4.Click OK. Proceed with step 4 in How to select track segments.

Notes

▪In some cases the number of samples available for smoothing can be less than the averaging interval entered. For example, in tracks with missing samples or at the beginning of the track. In such cases EthoVision XT uses the samples available in the specified interval. See Averaging interval

▪When the velocity is between the two thresholds, the current state of the subject does not change relative to the previous sample.

▪For Movement, it is possible to select different thresholds for nesting (see above) and for analysis (see Movement in the Analysis profile). You should either use the same thresholds or make the thresholds in your analysis profile more restrictive, so that the variable specified in the Analysis profile is in effect a fine-tuning of your nesting criteria.