Water supply & lick tracking
An important addition to the project this year is the inclusion of a water delivery system. The water delivery will serve as a reward to train the mice to associate a specific odor with a positive emotion. In addition, we need to monitor the licking behaviour of the mice to assess their emotional state during training and testing.
The criteria
The water should only be supplied during training; during testing, the water supply will be empty.
The water release system should not be adjusted during a training session.
The water release should be linked to the odor chosen by the GUI during training.
The licking behaviour of mice will be tracked during both training and testing.
The lickometer capacitor
A lickometer is a device used in neuroscience research to monitor the frequency and quantity of rodent licking in response to various stimuli, such as food or scents. It is equipped with sensors to register each lick, assisting researchers in measuring and analysing the animals' responses to different conditions or treatments. Tracking the licking behaviour of mice during olfactometer experimentation can provide insights into their emotional state because licking is often associated with both positive and negative emotions in rodents.
For example, increased licking can indicate a positive response, such as enjoyment or anticipation of a reward, while decreased or inhibited licking may suggest a negative emotional state, such as fear, anxiety, or aversion to a particular scent. By observing and quantifying licking behaviour in response to different olfactory stimuli, researchers can assess the affective valence or emotional significance of those stimuli to the mice.
This approach allows researchers to investigate how various odours impact the emotional states of mice, providing valuable information for understanding the neural mechanisms underlying emotional processing and behaviour.
Capacitance
This type of device is based on the principle of capacitance: the ability of a system to store electric charge. These sensors detect changes in capacitance to determine the presence of proximity of objects.
Capacitance is a fundamental electrical property that describes the ability of a system to store electric charge. It is defined as the ratio of the electric charge on one of the conductors of a capacitor to the potential difference between the conductors. In simple terms, capacitance determines how much electric charge can be stored in a capacitor for a given voltage.
In this project we will use capacitive touch sensors that are a type of electrical sensor that detects touch or proximity by measuring changes in capacitance. When an object, such as a finger or mouse tongue, comes into contact with the sensor it causes a change in capacitance that can be detected by the sensor’s electronics. Capacitive touch sensors typically provide a digital output signal indicating whether touch has been detected or not. This output can be used to trigger various actions, such as button presses, gestures, or cursor movements on touchscreens. Capacitive touch sensors are widely used in various electronic devices and systems, including smartphones and touchscreens.
In our project, we've developed a custom capacitive sensor to detect mouse licking behavior on a copper wire encircling a water tube. Our Arduino-based setup includes two LED diodes that illuminate at different threshold levels, calibrated based on research findings. This allows real-time monitoring of licking activity. Our sensor operates by detecting changes in capacitance when a mouse's tongue touches the copper wire, providing accurate and non-invasive data for studying mouse behavior. This innovation offers a cost-effective solution for researchers in neuroscience, pharmacology, and behavioral science, advancing animal research and welfare.
The design
Commercial lickometers are available, however are often found at a steep price. So, we have designed a DIY lickometer based off of the design published by Hayar et al. (2006).
The published design uses this principle so that the moment the mouse tongue touches the water spout, the circuit is closed and a signal spike is detected by the software. For our design, we replaced the A/D converter with our existing Arduino setup. A simplistic overview is demonstrated below:
Our idea for this segment of the project was to create a comprehensive system seamlessly integrating water supply and lick tracking functionalities. The decision to control water supply using the same Arduino responsible for solenoid valve operation stemmed from our desire to synchronize water delivery with specific odors, a requirement stipulated for our project. By aligning water and odor release on a single click, researchers can precisely control experimental conditions. Leveraging the resources available at Open Lab, we incorporated a water solenoid valve into our setup, following the assembly instructions provided. As for lick tracking, we've devised a plan to employ a separate Arduino (for better synchronization of this part you can read in Past & Future part). This Arduino will accurately monitor the frequency of mouse licks on the water bottle tube, facilitating precise data collection and analysis.
The assembly
Capacitive Touch Sensor
1. Finding Material
For building capacitive touch sensor you will need is the Arduino, bread board, two 220 Ohm resistors, one 1 MOhm resistor, some wires, copper wires, 2 LED diods and water bottle.
2. Building the set up
First, establish a connection by wiring the ground of the Arduino to the ground of the breadboard. Next, link the ground of the breadboard to the ground leg (the shorter one) of LED diodes equipped with 220 Ohm resistors. Ensure the positive leg of the LEDs is connected to digital pins on the Arduino, such as pins 13 and 12. Now, introduce a 1 MOhm resistor onto the breadboard. Connect one leg of this resistor to pin 4 and the other to pin 2, designating them as input and output respectively. On the pin 2 side of the resistor, attach a wire that is left unconnected on the other end. This unconnected side of the wire will serve as a capacitive touch sensor, activating the LEDs each time it's touched.
3.Codes
Before you can use the codes provided for the capacitive sensor with Arduino, make sure to download the CapacitiveSensor.h library. Then, you can simply copy and paste the provided codes to start using the sensor.
4.Connection to the water bottle
Wrap a copper wire around the end of the wire designated as the capacitive touch sensor. Then, connect the other end of the copper wire to the nozzle of a water bottle set to release water when triggered. When the capacitive touch sensor is touched, it activates the LEDs, while simultaneously prompting the water bottle to dispense water for a mouse to lick.
Video of how to build cappacitive touch sensor
Video of how capacitive touch sensor would work
Water Supply
1. Finding Material
For building water supply you will need is the Arduino, soldering board, water solenoid valve, transistor, power supply and wires.
2. Building the set up
To control a water solenoid valve with the Arduino, additional components like transistors and a power supply are needed due to the Arduino's limited power. Transistors amplify the Arduino's signal to power the valve, with their ground connected to the Arduino's ground. The Arduino's digital pin sends PWM signals to the transistor's base for precise control. A separate power supply provides the necessary voltage and current, connected to both the valve's positive terminal and the transistor's collector. The power supply's ground connects to the valve and transistor ground. All components are securely connected on a soldering board to prevent short circuits, enabling effective valve control by the Arduino.
3.Connection to the water bottle
Following the assembly of the control setup, we integrated the water bottle and valve system with tubing. Precise connections were crafted by securely bonding the components together. We linked the tubing intended for mouse access to a capacitive touch sensor using copper wires, ensuring reliable connectivity.
Video of how to connect water supply
Video of final water supply set up