Knowledge Base

Analysis of Trial Control Data

Devices such as the Lickometer and PhenoWheel send data to EthoVision XT at fixed times, every two seconds for the Lickometer and every 60 seconds for PhenoWheel. At each sample time, EthoVision XT reads the data since the last reading event:

• For the Lickometer: number and duration of licks.
• For PhenoWheel: number of rotations.

The reading events are not in sync with the trial start and stop. This means that:

• The data of the first reading event after the trial start also include some time before the trial start (< 2 s for Lickometer, < 60 s for PhenoWheel). This time is included in the results.
• The data between the last reading event and the stop of the trial are not included in the results. This time is again < 2 s for Lickometer, < 60 s for PhenoWheel, depending on when the trial stopped.

In most cases the two discrepancies have no effect on your data when the trial lasts at least a few minutes or hours, like in typical PhenoTyper tests.

Tip: If you want the devices to have another sampling rate, contact Noldus.

Hardware State Variable

A variable based on a Hardware continuous variable. You can, for example, define a Hardware state variable Number of dropped pellets is equal to or greater than 1 and calculate, for instance, the duration of this interval.

How to Add a Hardware State Variable to an Analysis Profile

1. In the Experiment Explorer, right-click Analysis Profiles and select New, or click an existing profile.
2. Click the Add button next to Hardware state.
3. The Hardware state variable window opens. From the Device type list, select the hardware device you want to calculate statistics for. For example, if you want to analyze the signal from your pellet dispenser, select Pellet Dispenser (PTPD-001x).
4. In the Device list the name of the hardware device will appear as you defined it when you assigned the device to the arena.
5. From the Signal list, select which signal you want to analyze. For instance, for the pellet dispenser you can select Number of drops or In error state.
6. Set the appropriate Value (threshold) or select the value you are interested in. For instance, for Number of drops set a threshold of equal to or greater than 1; for In error state select true or false.
   • Cumulative value: Select this option to calculate/visualize the cumulative value of the signal.
7. Click the Trial Statistics tab to choose the statistics for the dependent variable. Click the Group Statistics tab and select additional statistics if you want summarized statistics over all trials, or the groups of trials defined in your Data Profile. Next, click Add. For details, see Calculate Statistics in the EthoVision XT Help.

Application

You can use Hardware state variables to analyze, for instance, how long a light was on. You can also use Hardware state variables to analyze learning behavior. For instance, when training an animal you may want to know how long it takes before it completes a task (and receives a food pellet). For this purpose, you can calculate the statistic Latency to first for the Hardware state variable Number of drops greater than or equal to 1. For naive animals the latency will be high at the start of the training and will decrease as the animals learn the task in subsequent trials.

Please note that the following question requires a different procedure: What was the average time between "light on" and "lever press" in a learning experiment? It is not possible to define a variable based on two separate hardware events. To answer this question, define a Free interval using hardware events. For more information, see Free interval in the EthoVision XT Help.

Free Intervals Based on Trial Control and Hardware Data

Free intervals are the most flexible solution to analyze slices of time which go from an event, or time, to another event or time. You can use them in the Analysis profile and in the Data profile.

Example: In a DanioVision experiment, analyze the speed of the subjects in the 5-s time interval before the onset of the light stimulus, and in a second interval, in the 5-s time interval after the onset of the light stimulus. Because you want to analyze the speed within the intervals, define those intervals as Free intervals in the Data profile.

How to Add a Free Interval to an Analysis Profile

In the Analysis profile, under Custom Variables, click the Add button next to Free interval. For more information, see Dependent Variables in Detail > Custom Variables in the EthoVision XT Help.

How to Add a Free Interval to a Data Profile

In the Data profile, under Nesting, click the Add button next to Free interval. For more information, see Analyze Track Segments > Nesting over a free interval in the EthoVision XT Help.

The Analysis Results

To Calculate the Statistics

1. Click Statistics & Charts in the Project Explorer. The analysis window that appears has the tab Trial Statistics for the analysis results per trial and Group Statistics & Charts with statistics and charts from the summarized results over different trials.
2. If you have different filters, data profiles, or analysis profiles, make your selection on the toolbar.
3. Click Calculate.
4. Optional: Click the Layout button to modify the layout of the results table.

Source: EthoVision XT 18 - THC - Trial and Hardware Control, Noldus Information Technology