Animal husbandry – Confining or housing – For experimental purposes
Reexamination Certificate
1999-06-22
2001-08-14
Swiatek, Robert P. (Department: 3643)
Animal husbandry
Confining or housing
For experimental purposes
Reexamination Certificate
active
06273026
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS N/A
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT N/A
1. TECHNICAL FIELD
The present invention is directed to a system and method for automatically measuring an animal's response to its environment in a behavioral test to provide an indication of the animal's mental or emotional state.
2. BACKGROUND OF THE INVENTION
The Porsolt Forced Swim test is an accepted behavioral test performed to assess depression-like behavior in small animals such as rodents. This test is used for initial screening of new drugs for treating human affective disorders such as depression, stress, anxiety, psychosis, etc. This test is also used for screening genes involved in the etiology of human affective disorders.
In order to perform a Porsolt Forced Swim test, an animal is placed in a tank of water which has been filled to a level that is deep enough so that the animal is not able to support itself on the bottom of the tank, but that is sufficiently far from the top edge of the tank so that the animal cannot climb out. Most animals will swim or attempt to climb actively for some time after being placed in the tank. But gradually, the activity of the animal will lessen, presumably as the animal realizes that it cannot escape. As this happens, the animal will gradually spend more and more time simply floating on the surface of the water. The time, or the fraction of a fixed period of time, during which the animal actively swims and the time during which the animal floats is measured by human observation and used as an indication of the affect of the animal. Less time swimming and more time floating denotes “behavioral despair,” an animal model of depression.
In order to score a Porsolt Forced Swim Test, the swimming of the animal is typically videotaped and the amount of floating and swimming is timed with a stop-watch or hand held counter. Although the Porsolt Test itself is very simple, the procedure for scoring the test is laborious and inherently subjective since criteria for floating or for active swimming or climbing may vary from one observer to another or even from time to time for a single observer.
BRIEF SUMMARY OF THE INVENTION
In accordance with the present invention, the disadvantages of prior systems for measuring, evaluating and/or scoring behavioral animal tests used to study or treat human affective disorders have been overcome. The system and method of the present invention automatically measure an animal's response to his environment in a behavioral test to provide an indication of the animal's mental or emotional state. The system and method provides an objective measurement of the animal's behavior quickly, reliably and reproducibly. It is capable of detecting subtle differences in behavior with much greater resolution than is possible with human observation.
More particularly, in accordance with the present invention, a pair of spaced electrodes are positioned in a tank of water in which an animal is placed for at least partial immersion of the electrodes. A current is applied to the electrodes and the voltage across the electrodes is measured to provide a waveform, the amplitude of which varies with the height of the water in the tank to provide an indication of the animal's behavior. The signal from the electrodes is then processed to provide data representing the behavior of the animal as indicative of the animal's mental or emotional state.
In accordance with one embodiment of the present invention, the electrode signal is processed to determine the energy of the perturbations in the water caused by the animal's movement. This data is used to provide a graphical representation of the animal's activity over time. The data is also compared to one or more thresholds to distinguish various types of behavior. For example, one threshold distinguishes between electrode signals that are indicative of the animal swimming and that are indicative of the animal floating. With this data, a graphical representation can be generated to illustrate the relative amounts of time that the animal was swimming and floating during a given test.
In accordance with another feature of the present invention, the electrode signal is filtered to remove low frequency components of the signal associated with movement of the water in the absence of animal movement. This filter allows the system to distinguish between water perturbations at the resonant frequency of the tank that will continue long after movement of the animal has stopped. Further, in order to compensate for the variability of the conductivity of the water used in the tank, the data is normalized with respect to the conductivity of the water when at rest.
These and other advantages and novel features of the present invention, as well as details of an illustrated embodiment thereof, will be more fully understood from the following description and drawings.
REFERENCES:
patent: 4626992 (1986-12-01), Greaves et al.
patent: 4723511 (1988-02-01), Solman et al.
patent: 5140855 (1992-08-01), Gruber
patent: 5307052 (1994-04-01), Harrison et al.
Ferster David
Redei Eva
McAndrews Held & Malloy Ltd.
Northwestern University
Swiatek Robert P.
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