Imétronic™ Freezing file format
Imétronic Freezing™ file structure...
Imétronic™ Freezing data files are the output of the program Freezing for Windows that controls the Imétronic™ fear conditioning equipment. The system uses a grid of 24x16 infrared beams to monitor position and movements of the animal. Imétronic™ Freezing data files can contain position data of several sessions. Wintrack imports Imétronic™ data files assuming that they store all sessions of a single animal and maps each session to a separate trial. The expected file extension is .DAT. For details on the structure of Imétronic™ data files please contact the following address:
Imétronic, Ch. Darracq
Parc des ECHOPPES - 156, avenue J. Jaurès
33600 Pessac, France
0033 5 5698 6817 Fax
Reading Imétronic data...
The Open Case Document command recognizes Imétronic™ data files automatically and converts them to Wintrack case documents. Time, date, and session duration are stored in the trial notes. Position data are imported as path, whereby each beam break event generates a new data point. Wintrack offers the option of inserting additional data points to improve temporal resolution (see below) and therefore prompts for a sampling interval. During import Wintrack automatically sets goal position information to 'none' and automatically activates the Case Properties command, because Imétronic data files contain no case properties information. You may also specify a setup version if you plan to work with custom setup files. Note that the Analyze Case Document command provides no predefined variables that are specifically tailored to fear conditioning data. Analysis of such data usually requires advanced features that are only available with custom setup files and custom variable definition files.
Imétronic beam break events are time stamped (precision 0.1s) and specify the subject's position in terms of beam number (1-24 vertical left- right, 1-16 horizontal top-bottom). Beam numbers are mapped to Wintrack's internal -16384 to 16383 coordinate space using the following formulas:
x = 655 (2n-25) y = 655 (17-2n)Vertical beam 1 is mapped to Wintrack x = -15065 and vertical beam 24 to 15065. Horizontal beam 1 is mapped to Wintrack y = 9825 and horizontal beam 16 to 9825. The actual distance between beams is 10mm. Correct scaling is obtained if 0.2502m x 0.2502m is specified as arena size.
Combining Imétronic and event data...
Imétronic™ Freezing does not allow to record freezing or grooming as separate events. Alexei Vyssotski has developed MICE, a DOS based utility that permits to use the PC keyboard to record grooming and freezing of two mice during a fear conditioning experiment. If configured properly, the utility will also record tone and shock as individual events. The utility produces a separate ASCII format output file for each session. Wintrack imports this ASCII output as events and merges it with the path data imported from the Imétronic™ data files. Wintrack expects MICE output to be stored in the same folder as the Imétronic™ data file and to be named as follows: file name = same as Imétronic™ data file and extension = nnn, where nnn indicates the session number (.001, .002, etch).
During import of MICE output each change of the event status is mapped with 0.1s resolution to a data point whose time stamp indicates the end of the event. If an Imétronic™ infrared beam break occurred at the same time, the event status change recorded by MICE is added to the existing data point. Else a new data point is inserted and xy position is copied from the most recent beam break event. Because Imétronic™ beam breaks are not per se associated with event data, all data points in the case document are automatically supplemented as necessary with event information reflecting the current event status recorded by MICE. Events that occurred after the end of the Imétronic session are ignored. MICE event codes are mapped to Wintrack event keys as follows:
Controlling temporal resolution...
Imétronic™ Freezing does not use a constant sampling interval. If the animal freezes a lot and triggers very few beam breaks, data points may become separated by very long time intervals. Similarly, Alexei Visotsky's MICE utility does not record any data if the status of the animal and apparatus do not change. Wintrack does not require constant sampling intervals and has no trouble handling such data. However, data with long intervals between data points may produce false results if one analyzes specific time windows within a session. Events that lasted beyond the end of the window will be lost. In addition, the duration of events that started before the begin of the window may be determined incorrectly. To circumvent these problems when importing data stored by Imétronic™ Freezing and MICE, Wintrack offers the option of inserting additional data points at a regular sampling interval. When Wintrack prompts for a sampling interval during the import process, specify 0 if no points should be added. If you plan to analyze time windows, a sampling interval should be specified such that a data point will be available for each planned window border. Note that independently of any specified sampling interval, Wintrack inserts a data point 0.1s before each beam break if more than 0.5s have elapsed since the preceding break. These additional points approximate the actual end of a potential immobility period.
Completing position and event information...
When inserting additional data points or when interleaving position-less event data with Imétronic™ data, Wintrack always copies the exact position information from the most recent infrared beam break. Similarly, as necessary event key status is copied from the next available recorded event. Because no interpolation routine is used, analysis of enhanced and merged data can always rely on the fact that all position changes correspond to actual beam breaks recorded by Imétronic™ Freezing and that all status changes of the event keys were actually recorded by Alexei Visotsky's MICE utility.
Additional information...
- For an overview of Wintrack documents and files see Wintrack documents and files.
- For more information on case documents read Inside case documents.
