Brown Institute for Brain Science

Elevated Zero Maze

Rationale of Test

This task pits the natural curiosity of mice against an inherent fear of new and open exposed places. As a mouse overcomes its fear of a new environment, their exploratory behavior increases and they become more willing to fully explore new places. Anxiety-like behavior is assessed by the time and entries into the open relative to enclosed sections of the maze.

Apparatus

The apparatus is constructed of white acrylic and consists of a round 9cm wide track (56 cm diameter) that is divided into four equal sections. Two opposing sections of the track have 20cm tall walls while the remainder of the maze remains open. The maze is set up under a near infrared sensitive digital camera connected to a computer with digitizer board and automated 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, a mouse is placed in an open section of the maze and their behavior is recorded for a period of 10 minutes. The number of entries into both the open and enclosed sections is recorded (an entry is when the center mass of the animal enters into a section of the maze); the time spent in those two areas; and the frequency of center crosses is also recorded. Anxiety-like behavior is measured by the relative amount of exploration devoted to the open sections of the maze relative to the enclosed sections. This is quantified by two indices: (i) percentage of time spent in the open sections and (ii) percentage of entries into in the open sections.

Interpretation

A greater avoidance of open sections 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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