The Tehuti Brain Scanner started with a crystal ball from AliExpress. My daughter studied psychology in Nijmegen and because I am also a psychologist, our mutual gifts are often brain-related. She gave me this crystal ball with a beautifully engraved 3D model of a human brain as a Christmas present. If you illuminate such a ball from below, you see the model in all its glory. However, I also have a drawer full of lasers in all kinds of colors and sizes. What will happen if…

Point lasers turned out not to be very spectacular. However, a red laser with a lens in front that makes the laser beam fan out into a line exceeded my wildest expectations. With a blue light from below, the red laser line illuminated a slice of the brain with razor-sharp clarity. As fascinating as watching a campfire. It reminded me of the principle of modern medical scanning equipment such as MRI and CT scanners that map your brain slice by slice. If I could make this laser height-adjustable…

Around the same time, a microcontroller with a high-resolution AMOLED screen came onto the market. This technology uses organic materials similar to the way fireflies make light. It provides beautiful rich colors with low energy consumption. You probably already have this technology in your latest mobile phone. I had worked with a screen before at the Marconi, but that was a monochrome screen with low resolution: black-yellow with 128×32 pixels. Here I suddenly had 536×240 pixels at my disposal with 65,536 different colors. This also made it possible to use photos.

An ESP32 S3 is a very modern and powerful microcontroller in 2024 that can even play the classic 3D game DOOM. But it is not yet a full-fledged computer. Every photo therefore had to be carefully compressed to take up as little storage space as possible. To compose the screen I had to use “sprites”, a technique I remembered from the days of the Commodore 64.

Using non-standard fonts also proved difficult due to the limited storage space. The font I used for titles on the screen interfered with the motor of the laser slider. Every time a title with that font was on the screen, the laser slider stopped. In the end I designed a font myself for the titles and another for the subtitle “Brain Scanner”.

I wanted to illustrate the possibilities of an MRI scanner with the screen. The first mode was therefore a complete scan from bottom, the brain stem, to top. I found a series of 24 MRI ‘slices’ on the internet that corresponded very well with 24 steps of my laser. With each step of the laser I let the ball rotate once, which I illustrated on the screen with a circular structure of the scan image.

A second mode is mapping the emotions in the human brain. Here the laser can remain at one height, but we offer the test subject a photo with certain emotions each time. The scan then shows which areas in the brain are activated.

I added a simulation of a heart rate monitor, including sound effects, to also illustrate the effect of certain emotions on the heart rate. With frightening photos you see and hear the heart rate accelerate.

A variant of the emotion research is a commercial application, in which the effect of internationally known commercial brands on areas in the brain is investigated. I have no idea whether this is already done in practice, but if I can think of it…

A next application is research with various psychological tests. The most commonly used test for diagnosing brain damage, for example due to Alzheimer’s, is the Trail Making Test (TMT), a quick and easy to perform exercise that has been extensively researched. Here you give the test subject a set of points between which she has to draw lines twice. The first time the points are numbered from 1 to 25. This is easy for most people, including people with some brain damage. The second set of points is not only numbered from 1 to 13, but there are also points with letters: A, B, C to L. The test subject now has to connect the points in this way: 1 – A – 2 – B – 3 – C and so on. For healthy people this is only slightly more difficult, resulting in a slightly longer time to complete the task. For people with brain problems, however, this task is significantly more difficult. They take considerably longer to complete it than the first test. The time difference between the first and second test is taken into account when determining the diagnosis.

It turned out to be quite a job to simulate this TMT in C++, the programming language for simple microcontrollers. My knowledge of C++ was quite limited. I had used it in previous projects, but they were nowhere near as complex as the Tehuti. It has been around for a long time, but it is considered one of the more difficult programming languages. This is mainly because you have direct access to the memory of the microcontroller: with great power comes great responsibility.
Fortunately, 2024 was the year of the breakthrough of AI chatbots. I was able to submit my C++ problems to ChatGPT and usually got a useful answer. To be clear: none of the creative and visual aspects of the Tehuti were generated by artificial intelligence. It only helped me as a source of information to overcome programming problems.

After the Trail Making Test, I added some other classic psychological tests, such as the Stroop Color Test and the completely unscientific Thematic Apperception Test and Rorschach. In all simulations I have used ‘random’ values ​​at many points to give a realistic representation of reality. For example, our heart is not a metronome. Each heartbeat is slightly shorter or longer than the next. The difference is usually too small for us to notice, but subconsciously it might start to sound unreal. In the TMT, for example, I did not want the simulated lines between the points to be drawn perfectly straight. So I also added all kinds of randomisations here too, including the possibility of making an error every now and then, just like human subjects do.

I am very proud of the self-designed printed circuit board (PCB). This is the plate on which I solder the various electronic components. The microcontroller needs external sensors, resistors and transistors to be able to control the motors and laser properly. I designed the PCB in KiCad, an open-source program, with which I generated all the data that was needed to have the plate made in China. A week after sending the code I received the 10 beautiful printed circuit boards by mail.