Knowledge Base

Tracks and Integrated Visualization

• I defined "In zone" for two adjacent zones. In the Integrated Visualization, I see that the animal is in the two zones simultaneously
• I defined a free interval, and in the visualization I get an interval every other sample
• I plotted a variable in the Integrated Visualization. I only get a few values on the timeline. Why?
• I interpolated my data, but some variables including Elongation and Mobility still show missing values
• Screen recording could not be started
• There seems to be a delay between video and track
• The video image is not shown
• Video is choppy or does not play smooth
• The points are too small (or too large) or the traces are too narrow (or too thick)
• When I import UltraVox XT data, some calls are visualized as 1, others as 0.5. Why?
• The Integrated Visualization shows "Not calculated"
• The Data Preparation Report says "Failed" for some trials
• I cannot visualize a trial
• The name of the trial is not fully visible

Heatmaps

• A heatmap is plotted outside the arena, or merged with the heatmap of other arenas
• In the Heatmaps screen the Group Mean button is not available
• How can I merge heatmaps generated in different arenas?

Animal Appearing in Two Zones Simultaneously

This happens when a Zone exit threshold has been defined that is greater than 0, and the two zones Center and Border are adjacent. In such a case, when the animal moves from Border to Center, it is at some point considered to be in Center, but if it is not yet outside the zone exit threshold of Border, it is also considered to be in Border.

To prevent this, re-define the two zones in such a way that there is a gap between the two, its width being at least the same as the zone exit threshold.

Getting an Interval Every Other Sample

Most probably you defined a free interval based on two values of external data or a hardware variable, for instance:

• From Heart rate >= 300 to Heart rate >= 400
• From Number of pellet drops >= 1 to Number of pellet drops >= 10

When the value of the (resampled) variable reaches the second (higher) threshold, the interval ends and EthoVision XT finds the next sample that matches the criterion defined in From (first threshold). If the current value is higher than the first threshold, a new free interval is defined. However, if the value at the next sample is also higher than the second threshold, the interval is ended, resulting in a free interval of one sample. The search is repeated in the next samples, generating a repeating pattern.

In such cases, do not use a free interval. Instead, use a state variable that is based on the original external or hardware signal. You can find the state variable in the Analysis profile. For example, for the external data Heart rate, in the Analysis profile under External data choose Heart rate state. For a hardware signal, under Hardware choose Hardware state. There you can define the range of values you are interested in.

Only a Few Values Appearing on the Timeline

This may happen for variables which require two or more consecutive data points to be calculated. Consider the following examples:

• Your data contain missing samples. If one sample is missing, the variable is not calculated for one, two or more time points. For example, Distance moved is not calculated for two time points, and Turn Angle is not calculated for three time points.
• You may have applied the Minimal Distance Moved smoothing method. When using this method, if the distance between body points for time t and t+1 is lower than the Minimal Distance Moved, the body point at time t+1 is "moved" to the same coordinates as the point at time t. In this case Distance moved gets the value 0 (zero), but any variable that quantifies change in direction has no meaning and is therefore not calculated for that sample. If many samples in your track are filtered out this way, variables like Turn Angle, Meander, and Heading only appear in short segments. Because the filter removes data points that do not represent movement, these few remaining segments are a more realistic measure of the subject's behavior.

See also: How variables are calculated: Dependent Variables in Detail

Elongation and Mobility Still Showing Missing Values After Interpolation

Interpolation is only applied to missing body points to obtain valid x,y coordinates. When the subject is not detected, the subject's contour and surface area remain unknown. This is why variables such as Activity, Elongation, and Mobility still show missing values after interpolation.

Screen Recording Could Not Be Started

When trying to make a screen recording, you may receive an error message. This may be caused by the fact that older versions of the Noldus MediaLooks A/V filters are still installed, but the newest version was not installed.

1. Close EthoVision XT.
2. In the Windows Control Panel, choose Programs and Features, and remove old versions of Noldus MediaLooks A/V Filter.
3. Download the full installation ZIP file (see Install EthoVision XT), extract and browse to Drivers and tools > PreRequisites > MediaLooks. Copy Noldus Medialooks ScreenCapture 2.0 x64.msi to your EthoVision XT computer and run that file.
4. Follow the installation, then start EthoVision XT.

Delay Between Video and Track

The track is lagging behind the video or the other way round. This issue can only occur when you track live and save video.

Solution:

1. Choose Acquisition > Edit Tracks.
2. Choose the trial from the list at the top.
3. Play the video until the subject and the track are well in view. Tip: Choose a frame when the animal walks fast so you can see exactly in which sample the nose point overlaps with the subject's nose in the video.
4. In the Playback Control window, click the Offset button. This button is only available when you tracked live and saved video.
5. In the Synchronize video window that opens, enter a number of frames (negative or positive) to correct the discrepancy between track and video. Click OK when ready. For example, enter -1 to move the video one frame backward relative to the track.

Video Image Not Shown

This issue can occur in computers with two graphics cards: a primary (integrated) card and a secondary card, usually more advanced and powerful than the integrated one. The issue is solved when you choose which card EthoVision XT uses.

See also: The Camera Image Is Not Shown in the Arena Settings or Integrated Visualization

Video Is Choppy or Does Not Play Smoothly

This may occur if you play video at high playback speed such as 16x in the Integrated Visualization. The effect is worse if the secondary graphics card (GPU) which handles playback is less powerful.

Source: EthoVision XT 19 Help, Noldus Information Technology