Brown Institute for Brain Science

Elevated Plus Maze

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 an elevated maze with 2 open arms and 2 enclosed arms. Mice typically begin by spending the majority of their time in the enclosed arms. As the animal overcomes their initial anxiety, they begin to explore the open arms of the maze. Anxiety-like behavior is assessed by the relative time in and entries into the open relative to enclosed arms of the maze.

Apparatus

The elevated plus-maze is constructed of white Plexiglas, raised 70 cm above the floor, and consisted of two opposite enclosed arms with 14 cm high opaque walls and two opposite open arms of the same size (30 cm × 5 cm). The maze is set up under a near infrared sensitive digital camera connected to a computer with a digitizer board and video tracking software.

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, the mouse is placed in the intersection of the 4 arms facing an open arm and their behavior is recorded for a period of 10 minutes. The number of entries into both the open and enclosed arms is recorded (an entry is when the center mass of the animal enters into one arm); the time spent in those two areas; and the frequency of center crosses is also recorded. Anxiety levels are measured by the relative amount of exploration devoted to the open arms relative to the enclosed arms. This is quantified by two indices: (i) percentage of time spent in the open arms and (ii) percentage of entries into in the open arms.

Interpretation

A greater avoidance of open arms of the maze 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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