The time and space machine: continuous measurement of drug-induced behavior patterns in the rat

A simplified microwave-based motion detector for home cage activity monitoring in mice

Background

Locomotor activity of rodents is an important readout to assess well-being and physical health, and is pivotal for behavioral phenotyping. Measuring homecage-activity with standard and cost-effective optical methods in mice has become difficult, as modern housing conditions (e.g. individually ventilated cages, cage enrichment) do not allow constant, unobstructed, visual access. Resolving this issue either makes greater investments necessary, especially if several experiments will be run in parallel, or is at the animals’ expense. The purpose of this study is to provide an easy, yet satisfying solution for the behavioral biologist at novice makers level.

Results

We show the design, construction and validation of a simplified, low-cost, radar-based motion detector for home cage activity monitoring in mice. In addition we demonstrate that mice which have been selectively bred for low levels of anxiety-related behavior (LAB) have deficits in circadian photoentrainment compared to CD1 control animals.

Conclusion

In this study we have demonstrated that our proposed low-cost microwave-based motion detector is well-suited for the study of circadian rhythms in mice.

Electronic supplementary material

The online version of this article (doi:10.1186/s13036-017-0079-y) contains supplementary material, which is available to authorized users.

Behaviors in the Home Cage Reveal Toxicity: Recent Findings and Proposals for the Future

Nervous system impairment is prominent among signs of chemical toxicity in humans and animals, yet evaluation of behavioral and neurologic responses is seldom included in premarket screening. The sensitivity and validity of automatically recorded rodent locomotor activity, whether inside or outside of the home cage, justifies its inclusion in first-tier testing. Home cage behaviors are studied in the toxicologic laboratory using quantitative techniques from behavioral neuroscience. A practical, noninvasive, automated system was developed and validated at New York University, in accord with Federal guidelines for testing neurotoxicity. Effects of neurotoxicants on motor activity, eating, drinking, and the daily cycle of rest-activity indicate sensitivity to a variety of chemicals as well as new avenues to the understanding of mechanisms of toxicity. The rat's pattern of nocturnal activity is particularly sensitive to neurotoxicants and thus deserves additional attention. The coefficient of variability of various end points did not correlate with sensitivity to toxicants. This underscores the need for behavioral data to supplement theoretical considerations in test selection. The system's advantages are economy, high data capacity, humaneness, accessible and well-known end points, widely available equipment, automation, and the potential for direct comparisons of several different animal species.

Classification of rat behavior with an image-processing method and a neural network

Video recordings of 11 rats were digitized at five frames per second, and parameters describing the shape and the position of the rat were calculated. The behavior displayed by the rats was observed by an experienced observer. Separate neural networks were trained and validated, using the data for each individual rat. The neural networks correctly classified an average of 76.53% of the frames in the validation set and 98.18% of the frames in the training set. A single neural network was trained with 6 rats and validated with 5 rats. The neural network correctly classified 63.74% of the frames in the validation set and 82.85% of the frames in the training set.

A modularized infrared light matrix system with high resolution for measuring animal behaviors

The current study provides a new modularized infrared light matrix system (about $200 cost) which is designed to measure the horizontal gross or fine movements, vertical motion, clockwise or anticlockwise turnings, freezing time, and total distance traveled in rats. The system records the sequences of animal's activity in a computer-aided system with a resolution of 0.2 s in time or 1.6 cm in space, and permanently stores all the resulting data in file. The behavioral apparatus was tested for its sensitivity and usability by amphetamine-injected rats. It was found that intraperitoneal administration of amphetamine (1.25-2.50 mg/kg), but not normal saline, produced a dose-related increase in either the horizontal gross or fine movements, vertical motion, clockwise or anticlockwise turnings, or total distance traveled. However, amphetamine injections produced a dose-related decrease in freezing time. Apparently, most of the amphetamine-induced responses obtained by other detecting apparatus can be reproduced easily by the present apparatus. The current detection system possesses the following advantages: a) high resolution, b) high expansion potential, and c) precise and simplified algorithms for behavioral parameter analysis.

Three independent factors characterize spontaneous rat motor activity

A scaling approach was introduced recently to assess sequential and geometrical aspects of animal behavior. This study describes the relationship between different measures of unconditioned motor activity of rats. Specifically, the amount of motor activity was assessed using both a traditional photobeam break measure, counts, and the temporal scaling exponent, alpha, which describes the ratio of fast to slow behavioral micro-events. The sequential characteristics of the behavior were assessed by the dynamical entropy, h, describing the degree of unpredictability of future movements. The geometrical characteristics of rat motor activity were quantified by the spatial scaling exponent, d. Exploratory activity was measured by counting rearings and holepoking responses. A factor analysis of these measures was conducted based on results from 137 drug-naive animals that were tested for 1 h in the Behavioral Pattern Monitor. Three independent factors account for 77% of the variance. These factors can be described as the 'amount of activity', 'sequential response organization', and 'exploratory activity'. The factor loadings support the initial hypothesis that the geometrical structure of rat motor activity, i.e. the spatial scaling exponent d, varies independently from the amount of activity, i.e. counts. In addition, the distribution of these measures did not deviate significantly from normality suggesting that the z-scores of these variables, which have been used previously in the d-alpha plane description, are able to indicate significant changes of behavior. These results suggest that unconditioned motor activity is influenced by at least three independent factors. The independent assessment of these factors may contribute significantly to the understanding of the neural substrates involved in the organization of unconditioned behavior.

Behavioral effects of acute exposure to tributyltin chloride in rats

The behavioral effects of a single acute exposure to nonlethal doses of tributyltin chloride (TBTCl) were studied in male Wistar rats. The rats were given TBTCl by oral gavage at doses of 0, 6.3, 12.5, 25.0 or 50.0 mg/kg, and spontaneous motor activity (SMA) and acquisition of conditioned avoidance responses in a shuttle box were monitored. Body weight gain in the 50.0-mg/kg group was significantly lowered, but weight gain in the 6.3-, 12.5- and 25.0-mg/kg groups was comparable to that in the control group. TBTCl caused a dose-related decrease in SMA during the dark phase. The 24-h total daily and 12-h nocturnal activity was decreased at doses of 12.5 mg/kg and above. The acquisition of shock avoidance responses was inhibited in all TBTCl-treated groups in a dose-dependent manner, and the difference was significant for rats given TBTCl at doses of 25.0 mg/kg and above. The data indicate that an acute exposure to TBTCl can cause significant changes in rat behavior and suggest that SMA can serve as a sensitive index for detecting its toxicity.

A temporal and spatial scaling hypothesis for the behavioral effects of psychostimulants

A variety of psychoactive substances (amphetamine, nicotine, scopolamine, apomorphine, lisuride, and MDMA) were tested to examine whether a proposed scaling hypothesis is appropriate for the description of the amount and the structure of rat locomotor paths recorded in the Behavioral Pattern Monitor (BPM). The analytical approach was based on the assumption that the scaling behavior of a few collective variables may characterize sufficiently changes in the animal's behavior induced by different drugs. The temporal scaling exponent alpha, describing the ratio of fast to slow responses in the BPM, sensitively reflected the different stimulant properties of the substances. The spatial scaling exponent d, which relates the average path length to the resolution used to measure consecutive responses, was found to discriminate substances that had been separated previously via qualitative descriptions. Several behavioral response categories emerged from comparisons of the locations of different drugs on a two-dimensional d-a plane. Scopolamine, MDMA, lisuride, and high doses of apomorphine increased a while decreasing d, whereas amphetamine, nicotine, and caffeine produced an increased a with no change or an increase in d. Stereotypies could be identified on the opposite ends of the spatial scaling exponent scale and were interpreted as reflecting two kinds of perseveration. These results suggest that scaling approaches can be used to assess quantitatively the state of the animal based on its locomotor behavior and that the exponents can serve as collective variables providing a macroscopic description based on the microscopic elements of behavior.

Changes of spontaneous motor activity of rats after acute exposure to tributyltin chloride

The effects of a single acute exposure to tributyltin chloride (TBTCl) on spontaneous motor activity (SMA) in home cage were studied in male Wistar rats. The rats were given TBTCl intraperitoneally at a dosage of 0, 1.6 or 3.3 mg/kg, and the SMA was measured for five days after administration of TBTCl. Body weight gain in the 3.3 mg/kg group was significantly lowered, but that in the 1.6 mg/kg group was comparable to that in the control group. The SMA during light phase was not affected by TBTCl treatment. However, the SMA during dark phase was decreased in both of the TBTCl-treated groups. These decreases in SMA gradually returned to the control levels. The 24-hr total daily and 12-hr nocturnal activity in the TBTCl-treated groups were decreased in a dose-dependent manner. These data indicate that TBTCl possesses behavioral toxicity and suggest that the decreased nocturnal SMA is a sensitive index for detecting toxicity of chemicals in rats.