A Machine That Reads Your Feelings

Andreas Pettersson
Department of Chemistry
Uppsala University
March 2002

If you have been in a hospital and visited someone with an illness, you have probably seen the instrument that registers the heartbeats. If not, you've probably noticed it in movies. In my research, I am developing a device that in a similar way can measure feelings such as sadness, happiness and pain. A tool like this would be of great help in many ways for example, delivering proper medicine to the body when it is needed or maybe just to see if the patient is recovering well.

Why do I always forget names of people I just met? Why do I dream? These questions concerning the brain have always been pressing issues. Another such question is why we do have feelings if we just consist of molecules. This is of course a very difficult question to answer but there are some evidences that at least can give us an overall picture of how it all works. The function of the nervous system helps piece this puzzle. The body consists of a huge network of nerve cells. These are presented in every part of our body and they report to the brain if something unusual happens by sending out a message within the network to the brain followed by a response from the brain. The individual nerve cells are connected to each other by synapses, which make up a well defined junction. When one nerve cell is delivering a message to the other it releases chemicals of different types in the space between the synapses. These chemicals, also known as neurotransmitters, act as a code for the type of message that should be delivered. The receiving nerve cell picks up the chemicals and sends the message further.

I will measure the neurotransmitters that are released between the nerve cell synapsis. This is accomplished with a technique called microdialysis, a method that mimics the blood vessels in the body by selecting molecules of a specific size range to pass through the wall. In microdialysis, the wall consists of a cylindrical membrane that is attached to a plastic tubing. The membrane is directly inserted into the region where you want to measure the amount of neurotransmitters, in this case the brain. Inside the microdialysis tubing there is a flow of fluid called perfusion fluid which is similar to the fluid in the space between the synapses, this fluid however does not contain the neurotransmitters released by the nerve cells. When neurotransmitters are released they will pass through the membrane due to a phenomenon called diffusion, into the microdialysis probe and then delivered towards a detector by the perfusion flow. The problem is that only small amounts of the neurotransmitters will pass through the membrane and of those who do pass will often be in too low concentrations. Imagine the microdialysis as a river. On the shore are different kinds of people, the neurotransmitters, which are competitors in a swimming contest. Some people can not swim or they think the water is too cold, some people cannot swim well and therefore may not make it to the goal (detector), while some people swim fast and without any problems just like some neurotransmitters can easily reach the detector. In my project I introduce ferries in the river. These ferries sail to the shore where the people are, stay there so that everyone can get on board and then sail towards the goal. Now, everyone can come along since the ferries have room for plenty of people, no one drowns and everyone will reach the goal at the same time. I introduce a supporting agent (ferry) in the perfusion fluid that will collect the neurotransmitters. The steady flow is replaced with a pulsed flow, where the exact same volume as the cylindrical membrane holds is pumped to the membrane area and stopped there for a while before they are sent to the detector. The result will be that neurotransmitters that normally don't reach the detector will do so and in high measurable amounts.

The focus of my research is the microdialysis set-up. There are however some steps between the microdialysis sampling and to get the data on the screen. These are the wash and the release of the neuropeptides from the supporting agent followed by a separation of them from each other, and finally, their detection. The detector, in this case a mass spectrometer, is a very sensitive instrument that measures (meter) a spectrum (spectro) of molecular masses (mass). It is so powerful that it can measure less than a few milligrams of specified chemicals dissolved in a swimming pool. The mass spectrometer delivers a spectra on the screen similar to the one obtained from heart beat machines but instead of heart beats it will show the amount of neurotransmitters which controlling the feelings.

The method is just in the first step of development. An effective device would make it possible to read how the body is feeling and based on that information deliver proper medicine to the patient. It will also be possible to investigate and discover in more detail what type and amount of neurotransmitters the releasing nerve cell codes consist of and from that information design medicines. The resulting drugs would be much more effective and have less side-effects.