Analysis of Neuronal Circuits

Which path does the information go during the information processing in the brain? Which methods are currently used for monitoring brain activity? A Professor of Molecular and Cellular Biology at Harvard University Catherine Dulac speaks on moving towards understanding cerebration.

How is vision achieved? Well, it starts with the eye, so there is a number of neurons in the eye that will detect the light, and then all there are the neurons in the retina that will help to process this signal and make sense — maybe already of different colors or the movement of a particular visual stimulus. This information is going to be sent to an area of the brain called the ‘lateral geniculate’, and from this it will be sent to yet other brain areas to the visual cortex, to the primary visual cortex, secondary, tertiary et cetera. So from this original stimulus in the eye you can see that the information will be transmitted through a chain of neurons that will go from one brain area to the other, and all of these will help to decompose, decode the visual information into what we ultimately will understand as a percept – a percept of light or an object moving, a beautiful flower, a piece of art.

Being able to record from the brain, that is, putting electrodes in the brain and understanding the language of neurons, which is a set of action potentials, was performed mainly in anesthetized animals for the longest time. But over the last decade or so techniques have evolved to now be able to do a similar recording or to be able to estimate brain function in awake animals and even in awake behaving animals, so techniques of electrophysiology, techniques of imaging also have really given [us] a window into how does the brain function in real time in an animal doing a specific task.

What are the neurons that decide that there is enough food, there is no need to eat any longer? So you can destroy specific brain areas, but these lesion experiments were done in the past. Now you can specifically modify, genetically identify neuronal population and activate it. And if you activate the right neuronal population, this could lead to an animal eating voraciously or refusing to eat although it’s in principle hungry. So this type of genetic manipulation of a circuit is really completely changing the way one studies the brain, which is now you need to identify a particular brain area, then you can identify the specific neuronal type that is involved in a particular brain function and now you can manipulate the activity of this particular neuronal function.