Let Us Put Our Brains in the Spotlight – Literally!

Abstract: Neurons are the working force in each vertebrate’s nervous system. These small cells have the important task of transferring information in the form of electrical charges called action potentials. Neurons make it possible for us to sense touch, process our environment, and store memory. To conduct studies on the brain outside of the body, one can culture neural cells in the lab. However, to accurately replicate our brain through cultured neurons is easier said than done. The formation of arbitrary networks must be accounted for when trying to emulate our inner environment. Arbitrary networks are not representative of the network activities found in vertebrate brains. In my work, I have been trying to solve these random network formations by seeding human neural cells in microfluidic devices, a labyrinth for cells. The principle of culturing neural cells in a microfluidic device with a chevron pattern made up of a V-shape is to lead cellular growth in a desired direction. When the cellular growth is under control, it may be possible to activaley create the types of network more representative for our brain. For instance, I have tried to form feedforward networks in microfluidic devices. A feedforward network is a sleek organised structure where information is transferred from one layer of cells, through one or several hidden layers of cells, and eventually reaches an output layer of cells. My results point to the cell’s viability is almost as good as when they grow freely. The activity is similar and the cells’ growth is alike. The cells are also able to follow the chevron pattern in the desired direction and with a little tweaking of the design we expect to be able to better steer their growth and enable the formation of more representative networks. Another aspect of my thesis was to evaluate the possibility of utlising optogenetics to these cultured neural cells. Optogenetics is a useful method to study and manipulate behaviour of animals and even singular cells. By transfecting the cells with the protein opsin, which is sensitive to light, it is possible to expose the cell to a visual stimulus wheruopon the cells open membrane channels and an action potential is elicited. Being able to control the amount of action potentials generated, we could potentially control how cells store memory. The information in form of memory is stored in the connections between neurons. One way to strengthen the connection is to generate multiple action potentials, which is possible with optogenetics. In my work, I found that it is possible to build an experimental setup and expose cells to visual stimulus as I simultaneously record the cellular activity. However, I did not add the opsin protein to the cells, meaning they were not actually sensitive to light. For future experiments, the opsin transfection should be performed to sensitise the cells to light. To conclude, my work covers some basic ground for further future studies. With my chevron patterned microfluidicdevices I was able to steer the cellular growth. The cultured cells therefore exhibit potential to form feedforward networks with strong connection between the cells. When applying optogenetics to these cultured cells in coming experiments, the possibility to study memory formation in these networks will be possible. To manually strengthen the connections between the neurons in the created networks by using light, the prospect for memory research on mammalian brains outside of the body will open many doors.