What does this part of brain do?

Sarah Genon writes about how a change in perspective, and large data-banks, could help us to understand the brain’s functions.

As you start reading these few lines you are engaging in a wide range of mental tasks, from reading the title sentence, to evaluating the option of further reading, maybe you visually screen the page to get an idea of its length and attractiveness before taking the decision to continue. Or perhaps you are thinking it is time for another coffee.

Just by wondering to yourself “what actually am I supposed to do today?” or “do I actually have time to read this article?“, your mind and brain create a cascade of thoughts and mental functions.

As neuroscientists, we wonder how this rich repertoire of mental functions is organized at the brain level. This remains a largely open question, and the main reason is actually that this is not the right question to ask.

Our recently published article in the Journal TICS (https://doi.org/10.1016/j.tics.2018.01.010) described how different behavioural functions have been assigned to brain regions. In line with previous authors (Poldrack, 2011), we discuss why a shift in the viewpoint is needed and propose some concrete research perspectives to support this view. Here I summarise this discussion.

Generally, asking the question “what does this part of the brain do?” raises in our mind ideas of functions that have been formulated from the study of behaviour. Humans have always tried to understand their own mind. We have pursued this aim through different behavioural sciences , mainly under the umbrella of psychology but also in related disciplines, such as philosophy, sociology, psychiatry, neurology and behavioural economics. In all these fields, researchers or clinicians have developed theories and models explaining behavioural processes, functions, and their interactions.

This investigation of the human mind across centuries by so many different disciplines has resulted in several concepts about the mind, such as “phonological lexicon”, “recollection” or “theory of mind”. These concepts, their related models and theories have significantly advanced our understanding of the human mind and behaviour, and more importantly, they have contributed to our understanding and treatment of dysfunctions. As any aspects of behaviour originate from one unique substrate, the brain, the question naturally arises “how do all these concepts relate to the brain?”

After a century of neuroanatomy of the human brain, it is well acknowledged that it is spatially organized into regions and networks. We could therefore intuitively expect that all the concepts from behavioural sciences could be assigned to specific brain regions and networks. Accordingly, several approaches have been used across the last decades to relate these concepts to the brain. To understand the outcomes of this multidisciplinary endeavour, one could begin by looking in the scientific literature for what researchers have written about the hippocampus. Many different concepts can be found, such as autobiographical memory (1), explicit memory (2), contextual memory (3), associative memory (4), incremental learning (5), recollection (6), encoding (7), retention (8), consolidation (9), novelty detection (10), spatial navigation (11), scene imagination (12), creative thinking, flexible cognition (13)… This looks like a conceptual chaos.

However, it is certainly true that the hippocampus plays a role in autobiographical memory, scene imagination and spatial navigation. The point is that, all those concepts from the study of behaviour can be related to the hippocampus, but this is not what the hippocampus does… Let’s look at this question from the brain perspective. The brain, its many regions and networks do not “name object”, “feel empathy” or “imagine a scene”. This is what humans do, but this is not what the brain does.

The current state of affairs in the study of brain structure-function relationships could be better understood by a simple metaphor. If several communities of researchers were studying the many final output functions that are performed by computers (such as a reminder for you to send an e-mail to your colleague for his birthday) while other communities of researchers were partitioning the hardware of the computers, then what would happen when those two groups of scientific communities tried to map their respective models and components to evidence produced by the other group? Obviously, a key would be missing to bridge the observed output to the hardware architecture: the list of basic functions underlying the many tasks that the computer can perform.

But how can we disclose this list of basics functions? That is, how can we find out the true functions of brain areas and networks? There is no straightforward approach for solving this issue. One approach to progress in this issue would be first to collect the extended pattern of behavioural functions to which each region and network is associated, in order to progressively develop new hypotheses “from the brain point of view”.

Across the last decades, tremendous efforts have been made to collect the results of neuroimaging activation studies in databases in such a way that it is now possible to identify, for any part of the brain, the hundreds of neuroimaging studies manipulating mental tasks that have reported activations in a given part of the brain. For example, if we look at the hippocampus, we can find that it has been activated during memory retrieval, spatial navigation, but also in relations to emotions and perceptual tasks.

Brain scans and psychometrics data (such as personality traits, cognitive skills and behavioural habits) have also been acquired in big population samples across Europe and the US and are another resource to solve our current issue. From these big datasets of the population, it is possible to identify significant relationships between parts of the brain and psychometric data. That is, we can examine correlation between grey matter volume of a brain region and a range of behavioural measures tapping into everyday functioning, such as cognitive flexibility, anxiety or spatial memory.

We could then combine the behavioural profile of any brain region revealed by the two types of scientific approaches (one based on aggregation of activation data and the other one based on big datasets of cerebral and behavioural measures). From this hybrid profiling of brain regions and networks, we could start developing new hypothesis on the basic operation that any part of the brain computes.

Then, to disclose any of the “hidden” functions computed in the brain, we have to rely on the unequal ability of our brain to derive meaning from specific patterns. Rather than having each scientist looking at association between one concept and the brain, we would have many scientists seeing the same whole picture of many concepts associated to a specific brain region. We can hope that many scientist brains looking from the same (brain) view at a colourful pattern of associations at the behavioural level could come up with new hypotheses. Of course, the scientific path is still long and winding, until we clearly understand the function of any brain region, but harnessing data aggregation for “community-based discovery sciences” can be the first step.

Sarah Genon is a researcher at the Institute of Neuroscience and Medicine, Brain & Behaviour (INM-7) in the Research Centre Jülich (Germany). She is engaged in the HBP Subproject 2: Human Brain Organisation.

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