By April Cashin-Garbutt

Neuroscientists often talk about understanding the brain, but what do they really mean by this and how will we know when it’s been achieved? Nine leading neuroscientists, who have given SWC seminars over the last year, shared their thoughts on what understanding the brain means to them.

1. Explain flexibility

“For me, understanding the brain would mean we could explain its flexibility and describe, step-by-step, why the same physical input to the brain can generate different outputs and also how the brain can use different inputs to generate the same outputs. If we can understand these two types of flexibility, then our understanding of the brain and designing of artificial intelligence would be much more powerful.” Dr Yu Mu, Principal Investigator, Institute of Neuroscience, Chinese Academy of Sciences

2. Comprehend how behaviours are generated

“For me, understanding the brain means trying to comprehend how behaviours are generated and what specific circuit elements in the brain do. We have many methods that allow us to record from lots of brain areas and cells at the same time and we have tools that allow us to perturb the brain, but what we are still lacking is an algorithm that captures what is computed in a brain structure and how this computation influences the generation of behaviour.

We can do behavioural experiments, we can monitor brain activity and interfere with it, but we don’t have a good formalised description as to what happens computationally in the network that explains why a perturbation affects behaviour in a certain way.” Dr Sarah Ruediger, Postdoctoral Researcher, University of California, San Francisco

3. Be able to build a brain

“I think understanding the brain will consist of clear, concrete computations we can assign to at least the different major brain systems and some understanding of how those systems interact. 

The litmus test for whether we have actually understood the brain, is can we build one? I think that doesn’t necessarily require building an exact replica of the brain, as we may be able to abstract away a lot of the biological detail and still reproduce a significant fraction of behaviour.” Dr Joe Paton, Champalimaud Centre for the Unknown

4. Generate new questions about the brain

“It’s important to distinguish biology from engineering. In engineering, we might have a goal like, ‘I want to get to the moon’. Once we got to the moon, that goal was achieved. But biology is not like that!

In biology, we have goals like ‘I want to understand decision-making’. But, what does it mean to understand decision-making? For me, ‘understanding’ means knowing which parts of the brain are involved, how (and when) they communicate with each other, what computations they are performing, and how they’re performing those computations.

Even if we have all those things and we achieve that level of understanding, more questions will emerge! That’s how it works with biology – you’ve end up going deeper and deeper. 

And we see that happen already: you might first ask, ‘To understand decision-making I need to know which are the brain areas that are involved and how are they active.’ But once you realise that, then you ask, ‘Wait a second, how do those neurons come to be that way? How did the animal learn to make those decisions? How did it go from a novice that knows nothing to an expert that can harvest rewards in an efficient manner? We need to know that if we want to understand decision-making.’ 

The more you learn, the more you realise that there’s so much more to know! And I think the same thing is true with the brain more generally. You want to understand how the brain gives rise to behaviour, and why that sometimes goes very wrong, so that we can treat diseases. We have some understanding of that now and we need to extensively deepen it. We need to better understand how brains generate behaviour, how diseases disrupt that process, and how recovery can take place.” Dr Anne Churchland, Professor in Neurobiology at UCLA

“We will never 100% understand the brain as every brain is different. However, we can understand basic principles and the longer we look, the more we will uncover. There are endless things we can do.” Dr Sarah Melzer, Postdoctoral Fellow, Harvard University

5. Make predictions

“I think probably more like an engineer thinks to answer that question: for me understanding means that I can explain something, make predictions based on those explanations, and perhaps most importantly take something apart, or break it, and put it back together and get it to work again. For me that’s what understanding would be. 

As a little girl, I used to watch my dad, who was a self-taught hardware engineer, take things apart and fix what was broken. This experience really imprinted on me and shaped what I think of as understanding. If you have something that’s in pieces and broken, and you can rebuild it: that’s understanding.” Dr Michele A Basso, Professor in the Departments of Psychiatry and Biobehavioral Sciences and Neurobiology, UCLA

“Understanding the brain means being able to predict how it will react in different environments and conditions, using as few parameters as possible. In principle, if you can get a supercomputer to simulate the brain’s every atom and their interactions, the brain’s activity should emerge naturally and we would be able to accurately emulate how the brain would work in a particular condition. But we wouldn’t understand anything: the model is way too complex and has too many parameters. So I think understanding necessarily means reducing the number of parameters without losing too much information or predictive value. The more we can do this, the more we 'understand' about the brain.” Dr Zahid Padamsey, Postdoctoral Research Fellow, University of Edinburgh

6.    Solve problems

“What does understanding the brain look like? At a minimum we have to be able to solve problems. What we figure out about the brain needs to help improve the quality of life for people. My work is doesn’t directly touch upon clinical applications, but this is always in the back of my mind when I am thinking about what types of questions to ask and how to think about our approach.” Dr Cindy Poo, Postdoctoral Researcher, Champalimaud Research

“I don’t think of my goal as to understand the brain – that’s too big for any one person to handle! I think of my goal as solving tiny problems, each one of which is like one thousandth of one percent of understanding the brain, or less. 

I take a very pragmatic attitude: if we can come up with an intervention that makes the burden of drug addiction, depression, or anxiety 2% less of a burden for 10% of the population, then we’re solving that problem. And that’s important. 

Understanding the brain in an abstract sense is important only to the extent that it can help solve problems. So I don’t care much about the general question of understanding the brain, but do care about solving the problems that people face. And if we’re solving those problems, then it doesn’t really matter whether we understand the brain or not.” Dr Ben Hayden, Professor Neuroscience at University of Minnesota