Brown Institute for Brain Science

Open Field Test

  1. openfield_2
  2. openfield_1

Rationale of Test

This task pits the natural curiosity of mice against an inherent fear of new and open exposed places. The mouse is placed in the center of the arena and typically begins by spending the majority of their time near the walls and in the corners. As the animal overcomes their initial anxiety, they begin to explore the central portion of the open field. Anxiety-like behavior is assessed by measuring the time and entries into the center relative to peripheral sections of the open field.

Apparatus

The open field apparatus consists of a (40 cm × 40 cm × 49 cm) white Plexiglas arena with a white floor. The apparatus is set up under a near infrared sensitive digital camera connected to a computer with a digitizer board and video tracking software. With the aid of tracking software, the arena is digitally divided into twelve equal sections.

Procedure

The testing apparatus is set up in a low light environment (typically ~4 Lux). Prior to and between testing sessions, the maze is cleaned with a 70% ethanol solution. To begin a trial, a single mouse is placed in the center of the arena and their behavior is recorded over a 10-min session. Anxiety level are measured by the relative amount of exploration devoted to the center quadrants relative to those located adjacent to the walls of the arena. This is quantified by two indices: (i) percentage time spent in the center quadrants and (ii) percentage of entries into in the center quadrants. An entry into a given quadrant is only registered if center mass of the animal crosses inside the quadrant.

Interpretation

A greater avoidance of central sections of the open field is used to indicate heightened levels of anxiety-like behavior.

Relevant Controls

Care should be taken to insure no group differences in motor or sensory function.

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