The Sound Attenuating Chamber is an isolation chamber that provides a controlled environment for sound, electromagnetic interference, and light. It is utilized for various conditioning experiments. It can also be used to study the effect of audiogenic stress on rodent behavior and bodily functions.

The Sound Attenuating Chamber can be utilized for several conditioning experiments since it is equipped with levers, nose poke apertures, a speaker, a shock grid (optional), and a food pellet dispenser for reinforcement. The chamber keeps external environmental noise from the laboratory, which can distract or affect the animal’s performance during experiments, and eliminates the need for operant conditioning. chamber.

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Documentation

Introduction

The Sound Attenuating Chamber is an isolation chamber that provides a controlled environment for sound, electromagnetic interference, and light. It is utilized for various conditioning experiments. It can also be used to study the effect of audiogenic stress on rodent behavior and bodily functions.

The Sound Attenuating Chamber comprises several adjustable features. It contains multi-layer soundproof insulation, a manual LED light, programmable ambient and IR lights, an automated IR light, an automated circulation fan, a camera holder, a syringe pump, an infusion pump, and a pull-put floor shelf that allows easy removal of waste materials. The chamber is equipped with two levers, two nose poke apertures, and two cue lights for conditioning experiments. The cue lights are placed above the levers or nose poke apertures and can be configured to produce white, red, green, or blue light. An infrared sensor is equipped with a nose aperture that allows automatic detection of nose pokes. The chamber is also equipped with a 20 mg pellet dispenser, which dispenses pellets as a reward if the subject meets the desired conditioning criteria. Moreover, the chamber can also be equipped with a shocker or frequency tone if needed. Since the sound-attenuating chamber is already equipped with equipment for conditioning experiments, it eliminates the need for having separate operant conditioning chambers placed in a sound-attenuating chamber, which is usually the case for several experimental studies. 

The Sound Attenuating Chamber keeps out external environmental noise from the testing area, which can distract or affect the animal’s performance during experiments. It also improves the quality of the auditory stimulus for auditory discrimination experiments since the inner walls of the chamber reduces the reflection of sound, which can cause distortions. Moreover, when multiple experiments with auditory stimuli are performed close to each other, an attenuating chamber is essential to eliminate interference between discriminating stimuli from different experiments.

Apparatus and Equipment

The Sound Attenuating Chamber is an isolation chamber equipped with multi-layer sound-proof insulation material, dual visible and IR light bulbs, a camera holder, and a pellet dispenser. The pellet dispenser is 20 mg; however, a 45 mg dispenser is also available. 

It also contains two levers, two nose poke apertures, and two cue lights. The nose poke apertures are mounted 1 cm above the floor on an interactive panel and measure 1.3 x 1.2 x 1.2 cm (width × height × depth). The interaction panel also contains the two levers, which are made of stainless steel. They are available in different widths: 1.6 cm for rats and 1 cm for mice. 

The chamber contains a syringe pump with an interior diameter of 12 mm. It has a configurable RPM of 0.5 – 60 pump speed. It also contains an infusion pump.

The chamber can also be equipped with a shocker grid if needed for additional conditioning protocols. The grid is removable and produces a shock current from 0.1 to 4.0 mA in 0.1 mA steps. The shocks can be controlled by software or administered manually. 

Training Protocol

Fill the pellet dispenser before starting the experiment. Remove the tray beneath the chamber and remove any waste material between test sessions. 

The following is a sample conditioning protocol to analyze resurgence behaviors using the sound-attenuating chamber. 

Phase 1 (Baseline Testing)

Place a subject in the sound-attenuating chamber. Illuminate the cue light on one of the levers. When the subject presses the target lever, deliver a food pellet. After that, when the subject presses the target lever, deliver a food pellet after a 15-second variable interval schedule of reinforcement. If the subject presses the other lever, deliver no food reward or consequences. Conduct twenty baseline sessions. After baseline sessions, divide the subject into three groups of six in which the target lever-pressing during the final three sessions is equal between groups. 

Phase 2 (Treatment)

Place the subject in the chamber. Illuminate the stimulus light on the target lever and illuminate one nose-poke aperture. However, don’t deliver the reward when the subject presses the target lever as done in phase 1. Instead, if the subject pokes its nose in the illuminated aperture, deliver a food pellet along with an alternative reinforcement according to a 15-second variable interval schedule of reinforcement. Conduct fifteen sessions. 

Phase 3 (Resurgence Test)

Conduct different treatments for each group during the resurgence test. For the control group, administer the food pellets in the same manner as Phase 2, such that the reinforcement contingencies remain the same. For the Resurgence-Control group, completely suspend the food pellets and food-correlated stimuli. For the Stimulus group, remove the tubing that connects the pellet dispenser to the food aperture. Therefore, nose pokes will only produce an audible click from the pellet dispenser without the reward. Conduct five sessions for each group. 

Literature Review

Investigation of resurgence behaviors in rodents using the Sound Attenuating Chamber

Craig, Browning, and Shahan (2017) investigated whether delivering reinforcer-associated stimuli during resurgence testing mitigated resurgence. The experiment was conducted using an operant chamber housed in a sound-attenuating chamber. The operant chamber was equipped with levers, nose poke apertures, cue lights, and a pellet dispenser. Eighteen male Long-Evans rats ninety days old were divided into three groups of six and used in the experiment. The experiment was divided into three phases: baseline testing, treatment, and resurgence testing. The food pellets were delivered after pressing the lever in phase 1 and after nose pokes in phase 2, each after a variable 15-second interval schedule of reinforcement. During resurgence testing, trials were conducted in the same manner as phase 2 for the first group. For the second group, pellet dispensing and cue illumination were suspended. For the third group, only the food-correlated stimuli were produced without delivering the food reward. Results indicated that resurgence was lower in the group that received food correlated stimuli than it was for the group that received no consequences for nose pokes. Moreover, target-lever pressing did not increase in the first group between the three phases. However, it resurged for the second and third groups.

Investigation of metacognition in rats using the Sound Attenuating Chamber 

Foote and Crystal (2007) investigated metacognition in Sprague-Dawley rats using an operant chamber housed in a sound-attenuating chamber. The experiment was divided into study, choice, and test phases. During the study phase, a sound was presented to the subjects to classify as short (2–3.62 s) or long (4.42–8 s). The choice phase comprised of presenting the subject with either one or two response options. During one response option, a single nose-poke aperture was illuminated that the subject had to select, which led to the duration test, and the subject was not allowed to decline the test. During both response options, both the nose-poke apertures were illuminated. If the subject poked its nose in one of the apertures (which indicated accepting the test response), it led to the insertion of two response levers, which led to the duration test. During the duration test, the subject had to discriminate between short and long noise durations. The presentation of a short noise indicated one lever as the correct response, and a long noise indicated the other lever as the correct response. Nose pokes in the other aperture indicated declining the test response, and no duration test was produced. During the test phase, six large pellets were given as a reward if the correct lever was pressed with respect to the duration of discrimination. On the other hand, an incorrect lever press produced no reward. Declining a response in the test phase produced a smaller reward of three pellets. Results indicated that when the discrimination of the noises increased, the rate of declining the test also increased. Moreover, the accuracy of selecting the correct lever also declined as the difficulty of the discrimination increased. 

Data Analysis

The following parameters can be observed using the Sound Attenuating Chamber:

• The number of correct lever responses
• The number of incorrect lever response
• The number of nose pokes in the correct nose poke aperture
• The number of nose pokes in the incorrect nose poke aperture
• Trial duration 

Strengths and Limitations

The Sound Attenuating Chamber allows conditioning experiments to be performed in a sound-controlled environment, eliminating the need to use operant chambers. It is equipped with two levers and two nose poke apertures, allowing the experimenter to utilize either or both during conditioning experiments. Moreover, the cue lights placed on the levers and nose poke aperture are configurable, so the experimenter can set the desired color during experiments or utilize different colored cue lights to challenge the subjects discriminating abilities. The chamber is also equipped with a speaker that can produce sounds within the frequency between 100-40,000 Hz. Moreover, it includes a pellet dispenser for delivering the food reward. The chamber can also be equipped with a shocker grid if needed. Therefore, the sound-attenuating chamber can be utilized for several different conditioning protocols since it is equipped with several different stimuli for reinforcement. 

Summary

• The Sound Attenuating  Chamber is an isolation chamber that provides a controlled environment for sound, electromagnetic interference, and light.

• It can be utilized for several conditioning experiments since it is equipped with levers, nose poke apertures, a speaker, a shock grid (optional), and a food pellet dispenser for reinforcement. 

• The Sound Attenuating  Chamber keeps external environmental noise from the laboratory, which can distract or affect the animal’s performance during experiments.

• The Sound Attenuating Chamber eliminates the need for an operant conditioning chamber. 

References

1. Craig, A. R., Browning, K. O., & Shahan, T. A. (2017). Stimuli previously associated with reinforcement mitigate resurgence. Journal of the experimental analysis of behavior, 108(2), 139–150. https://doi.org/10.1002/jeab.278
2. Foote, A. L., & Crystal, J. D. (2007). Metacognition in the rat. Current biology : CB, 17(6), 551–555. https://doi.org/10.1016/j.cub.2007.01.061