This Arduino project automates rat behavioral tests in Y-maze. It lets experimenter enter different programs
with 4x4 keypad and LCD 128x64 display. Programs are saved in memory and can be selected and used later.
Arduino plate controls over LEDs lighting and door opening, it also sends signals to data acquisition interface
event channel, which lets matching events in the maze with neural activity. Maze has middle LEDs, which draw animal's
attention, and two LEDs on each side, which clue animal on which way to run.
Middle LED lights on and off, then side LED lights on and off, then door opens (or stay closed, if thus
programmed). The times of lighting and delays between signals are determined by current program.
Arduino Mega, LCD 128x64, Keypad 4x4, LED (x5), servo motor, perforated circuit board, 12V adapter, 12V to 3.3V/5V buck step down power supply module, maze box, (data acquisition interface)
A total of 5 LEDs are used: 3 for middle signal and one for each side. It is important that LEDs are not too bright, as it can repel the rat. In our experiments we observed steadily wrong choices, as rats, even trained to food being on the side of light, avoided it and chose to go to the darker branch. It is a good idea to cover the LEDs with some semitransparent material, like paper or matte plastic, or at least turn them upward, so that animal looks on it from the side. This way it sees signal, but not bright light.
It is also important that the maze box itself is painted matte black from inside. Darker environment not only calms a rat and make signals more significant, but also makes sure that there are no reflected light that might confuse animal.
The plate is powered from 220v network through 12V adapter and 3.3V/5V power supply module, which also lets turning it on and off and reset.
Specific for the code. They can be changed in the script and in circuit.
LCD 128x64 - pins of Arduino Mega
GND - GND
VCC - 5v
RS - 41
R/W - 43
E - 45
PSB - GND
BLA - 3.3v
BLK - GND
There are eight pins on the keypad, which correspond to the following pins on the plate (left to right):
22 23 26 27 30 31 34 35
Example 1:
1M3m2S3s5D
1 - 1 second delay before middle light
M - Middle LED on
3 - Middle LED is on for 3 seconds
m - Middle LED off
2 - 2 seconds delay after middle light
S - Side LED on
3 - Side LED is on for 3 seconds
s - Side LED off
5 - 5 seconds delay after side light
D - Door opens
Example 2:
1M0m0S3s0*
In this example time of middle LED is 0, which means it won't light on.
* instead of D means that door won't open.
Side parameter is chosen before each round of experiment:
L / R / *
L stands for left side for animal. It is important to remember, as the experimenter is behind
the maze wall and should place food accordingly.
* is random. Script remembers previous sides and will never give one side 3 times in a row.
It's made in order to not cause habit to one side in animal.
This threshold is determined by the following code and can be changed according to the experimental needs:
int pickSide(){
<...>
if (sameSide >= 3){ // no more than THREE times on the same side in a raw
<...>
}
There are five screens for the whole interface:
- First screen: select program from memory or enter a new one
Select program A
New program D
- Enter new program
On this screen user types consecutive numbers of delay times in seconds for each step of program. They are spaced by pressing letters on keypad, hinted below on screen.
Example:
1M1m2S_
Enter time of side
C - finish entering B
B back to First screen
Entering ends with pressing #, which saves new program in memory and sends to Preparation screen
with new settings.
- Select old program
2. 3M0m0S5s3D 8
3. 1M1m2S3s0*
4. 1M1m1S1s1D
# select up A
* delete B - back down D
Three programs from the whole list are seen on one screen. Selected is the middle one (framed).
8 in the upper right corner shows the number of programs in memory. Max number is 20
# sends to Preparation screen with selected program
* delets program from memory
B back to First screen
There are two ways to navigate through the list:
- A/D buttons shift list up or down one program
- typing program's number on the keypad. If entered number exceeds the number of programs, the last one will be selected.
- Preparation screen
2M2m2S2s2D
Set rat and door
# - ready B - back
On the first step rat should be placed behind the door in the starting chamber.
When # is pressed, servo motor closes the door.
B returns to Program selection
2M2m2S2s2D
A - left
C - right
* - random B - back
On the second step side should be chosen. Experimenter can either pick side themself or let program set it randomly. Chosen side will be shown in the upper right corner to let experimenter place food. B returns to the first step and opens the door.
- Experiment screen
2M2m2S2s2D L
# - start B - back
B returns to the second screen of preparation and lets change the side.
L shows that left side was chosen. It's the time to place food.
# starts program execution. After that it won't be possible to interrupt it.
During experiment executed parts of program will be underlined.
When middle and side LEDs light, and when door opens, a 5 ms signal is sent to event channel of data acquisition interface, which allows to match events in the maze with animal's neural activity.
There is one known bug I wasn't yet able to fix. If user goes to Select old program screen, then returns to the First screen and goes to New program, pressing any digit will make one of the old programs appear. It's usually not critical, but if it happens user should reset the maze and go straight to New program.
This software was developed as part of research work in the Laboratory of Neurobiology and Molecular Pharmacology of the Institute of Translational Biomedicine of St Petersburg University under the scientific supervision of Dr. Anna B. Volnova
