Imagine you were trying to understand how the human civilization works by observing our planet from the Moon. Being on the moon, you would not have much else to do, so this sounds like a nice hobby, right?
At first glance, you would spot two main types of regions, water and land, which would allow you identifying oceans and continents, but not much more than that: blue and brown areas... But then one morning, during your daily walk, you find in a crater a telescope that Neil Armstrong forgot to take back to the Apollo 11. This is great! Using this new, cutting-edge experimental technology you are now able to see mountain systems, islands and deserts where before you could only see blue and brown stains. You get completely absorbed in the analysis and classification of all these new geographical features and after a couple of weeks you have developed a much more detailed map of the Earth.
You are now very happy with your progress. However, even though the new map of the Earth provides much more information than the old one, you are still very far from understanding how different human societies work; for starters you don't even know whether they exist, but even if you did, you wouldn't know whether they 'grow' in the blue or the brown areas. But one day you make a great discovery when you realize that during the dark phase of the Earth (when the sun is not illuminating the side you see), the land regions are not completely dark but instead show blobs of light. You had seen these things before, but now it dawns on you that they are not random and actually follow specific patterns. And they seem to flicker! You elaborate your hypothesis: such blobs of light can be used as an indicator of human activity. Therefore societies grow on land! This discovery opens up a whole new world of studies: producing a detailed description of the light distribution across continents, analyzing the correlation between light and geographical features, studying the fast and slow variations in light intensity (why do they seem to flicker? why do they change from one dark phase to the next one? are these variations just due to noise produced by clouds?)... Months of hard work lead you to insightful discoveries such as the fact that light intensity is highly correlated with the land borders (there is more light in the brown areas close to the blue ones) and anti-correlated with deserts and mountains (no light on those places). So humans seem to prefer living in areas close to water and to avoid deserts and mountains. Another parameter that correlates with human activity is latitude: there is very little light on the south and north poles. "Temperature might be an important factor for the growing of societies", you write in your experimental notebook.
You now know a lot about human societies... and yet many questions remain to be answered. For instance, the green areas also seem to be anti-correlated with light. Why would people avoid trees? Are trees dangerous?... And there are many other things you don't know about human societies, things you cannot even imagine. You don't know they are organized in different countries, and you don't know that within each country people tend communicate using a language specific to that country. You don't know that people from some regions can travel to any other part of the planet in less than 24 hours, and that that same people can know what is happening in any other part of the planet in less than 1 minute…
Trying to understand the brain is not so different from the task I just described. Neuroscientists observe the brain with the experimental techniques there exist at the moment, and try to make sense of what they see. They collect information, analyze it and elaborate hypotheses. Then new instruments (like the telescope you found in the crater) for observing the brain are discovered that allow measuring its activity with more precision, or with a broader field of view, or in combination with another existing technique, and new questions can be answered about how the brain works (but many new questions arise). Sometimes is not a new technique, but a new perspective (like looking at Earth during its dark phase) what changes our understanding of how the brain does a particular task.
Also when studying the brain, we need to combine information coming from different sources so as to make sense of its intricate structure and functioning. A great example of this strategy is a study published in Nature last year, in which the authors presented the most detailed map of the brain so far: they actually found one hundred brain regions that had not been defined before, 100! How was this possible? Basically, they based their new Ultimate Brain Map in several anatomical and dynamical properties of 210 brains belonging to 210 healthy subjects: the thickness of their cortex, their brain activity, the connectivity between regions, the topographic organization of cells in brain tissue and the levels of myelin. And the key was to combine the information about these different parameters so as to discriminate regions that would have been merged together had they used a smaller set of parameter to build the map. For instance, two regions could have the same thickness and topography but at the same time be very different regarding their connections. Would you put these two regions together? It seems they are communicating with different areas so… The new map has 180 different regions of which, as I said, almost 100 are brand new. Therefore the amount of new information is huge and will certainly be useful in the near future. And yet, as when looking at the Earth from the Moon, there are still many things the map cannot tell us about how the different brain regions process information and communicate it to other brain regions. So we will have to keep on working. That's what science is about. A lot of work, a few discoveries and loads of unknowns.
There is however a big difference between youre possibilities to understand the Earth from the Moon and our possibilities to understand the brain: we can manipulate its normal functioning and study the outputs of such manipulations. This is an approach that has provided us with unvaluable knowledge about how the brain works. I will give you an example in my next post! In the meantime, I leave you with a nice video produced by the people in Nature about The Ultimate Brain Map.