Incoming signal - eyes have detected image - intelligent association is initiated - information is processed. It is a dog. Just now my eyes have noticed our lively and cuddly family dog Bernstein. He lies happily panting under a luscious green apple tree. Our brain is the creator of this scenerie. But how does the complex interconnection work in the network of millions and millions of nerve cells that make up our brain? The hot topic in research is organoids!
Basically, these miniature organs have gained popularity - deservedly. They are considered promising models for researching human physiology and provide important insights into the development of diseases. At the NMI Natural and Medical Sciences Institute in Reutlingen, a method has now been developed in close cooperation with the Max Planck Institute for Molecular Biomedicine in Münster and the University of Osnabrück that enables better recording of the activity of brain organoids. Nevertheless, the tissue-like, three-dimensional structure of the organoid is not the same as the human brain.
What are these mini-brains actually made of?
Brain organoids are cell assemblies of nerve cells. The cells that are necessary as basic building blocks for the formation of the brain organoid are generated from human, so-called pluripotent stem cells. These pluripotent cells can develop into all cell types of the body. Basically, the mini-brains are a random arrangement of nerve cells. However, in addition to nerve cells, other cell types can also be integrated, for example to improve the supply of nutrients. Piece by piece, the cells are attached to each other, resulting in a complex interconnection. In this way, not only "small brains" but also other "organs" can be grown in the petri dish. Although the neurons form a simplified network among themselves do not have the ability to control directional activities. Thoughts, as they arise in a human brain, cannot develop within the small "cell clumps".
The brain - a networking talent!
Basically, the complexity of the brain arises from the network activity of millions and millions of cells. These signals can be measured as electrical activity via electrodes and encode all incoming, processed and outgoing information. You remember Bernstein's exemplary perception process at the beginning of the article? Each area of the brain performs a different task. A signal arrives, is processed by various brain structures and associated in another with the cute family dog. In a brain organoid, there are no different areas that can map thoughts. Nevertheless, electrical activities can be measured. Are these activities comparable to those in the human brain? - No. The difference is the quantity and regularity. The small mini-brains only show spontaneous and significantly less activity.
Hammock for the mini-brain
One challenge with the small mini-brains: the small, roundish structure. This makes it difficult to measure the spontaneous electrical signals. The complexity inside the organoid can only be described inadequately with common measuring systems. Invasive electrodes that destroy the network or a limited number of electrodes impair the measurement.
To overcome these difficulties, the group of Dr. Peter D. Jones, group leader of Biomedical Micro- and Nanotechnology at the NMI in Reutlingen, has constructed a small, net-like "hammock" in which a large number of microelectrodes are embedded. When the organoid is placed on the hammock, it begins to grow through the meshes of the net. The integrated electrodes disappear inside the mini-brain, where they can record activity. Embedded in the microelectrode hammock, the brain organoids can be cultivated for over a year. This allows activity measurement during the development and growth of the cell aggregate. In the future, it would be conceivable to integrate chemical sensors to monitor the biochemical milieu, as well as a three-dimensional scaffold structure to allow even more measurement points in an organoid.
What's the point?
The Results of these activity measurements shed light on the fundamentals of neuronal network activity and provide valuable data on the development of neuronal connections. Findings like these are important because neuronal research in other model systems is ethically highly controversial. Primate experiments and human models are considered ethically unsound in many respects. However, we need to make progress in understanding and treating neurological diseases. Organoids are biologically like humans, but otherwise far from being human. The miniature brain overcomes the problem of unethical, human models and makes a great contribution to innovative in vitro research.
Isn't it nice to be able to perceive the world and see the dog next to a lush green apple tree? What do you think now? Feel free to share, we'd love to hear your thoughts!