Heading to point
The direction of movement of the nose, center or tail-base point of the current sample relative to a point of interest. See Define zones and Draw a point
If your experiment is set to Center-point detection or Color marker tracking, calculations are based on the center point.
Calculation
Heading to point is calculated in a way similar to Heading. The difference is that for Heading to point the reference line is the line that connects the previous sample and the point of interest. For Heading, the reference line is the line parallel to the x-axis.
Heading to point for sample k is the angle a formed by the segment joining the samples k-1 and k, with the line connecting sample k-1 and the point P (a point of interest or the center of a zone).
Range
Heading to point ranges from -180° to +180°. The closer to zero Heading to point is, the straighter the subject moves toward the point. Negative values occur when the subject moves to the right of the point; positive values in the other case.
Below: Example of Heading to point with positive and negative values in a water maze test. The platform has been specified as a target point. The chart shows Heading to point in the Integrated visualization (Analysis > Results > Integrated Visualization).
How to specify Heading to point
1.Click the Add button next to Heading to point.
2.From the Point of interest list, select the center of the Arena, center of gravity (COG) of a zone or a point you defined in the Arena Settings.
3.Complete the procedure to add the variable. See Calculate statistics: procedure.
Notes
▪If your experiment is set to Center-point, nose-point and tail-base detection, click the Body points tab and select the body points for which you want to calculate heading to point.
▪The mean, standard deviation and variance are calculated with circular statistics. See Statistics available
Use Heading to point to measure the subject’s orientation relative to a point of interest.
▪Morris water maze. Use Heading to point to determine the Heading angle error. The Heading angle error is usually determined after the animal has traveled a minimum distance, or after the first few seconds of each track. The Heading angle error at this point is the deviation from a direct line from starting point to center of the platform.
Below: The Heading angle error (a) in a water maze. The first two samples of the track are displayed. The arrow indicates the release point.
How? First, in the Data profile under Nesting choose Time, and select for example from 0 to 2 seconds. This means that analysis is done on the data points of the first two seconds of the track. Next, in the Analysis profile choose Heading to point and select the platform as point of interest. As Trial Statistic, choose Mean. For other water maze output variables, see also the EthoVision XT 19 - Application Manual.
▪Novel object test. Use Heading to point to determine the subject’s movement relative to an object. The assumption is that an animal is interested in a novel object when it is heading towards the center of the object.