‘Your expectations influence how you perceive the world’
Our brain determines the way in which we perceive the world. From the immense flow of information reaching our senses, it selects exactly those signals that are relevant. It uses our past experiences, memories, and goals. Cognitive scientist Kia Nobre unravels how our brain manages this. She received the C.L. de Carvalho-Heineken Prize for Cognitive Sciences for her research.
We may not always realise it, but the way in which we perceive the outside world is different for everyone. Our brain is constantly busy making predictions, selecting relevant sensory signals, and linking signals to information from our memory. ‘What we pick up from the external sensory stream is strongly shaped by our previous experiences, our memories, and also by our goals and motivations at a given time,’ says Kia Nobre, professor of translational cognitive science at Oxford University.
The reason: There are too many possibilities and distractions in the world to guide effective behaviour. Our brain therefore focuses our attention on the signals that are most relevant to us. There is also a huge amount of information available from within, in the form of memories. ‘Selecting and synthesising the relevant signals amidst all these distractions is essential for building coherent sensory perception, understanding and producing language, and performing everyday tasks like cooking or driving,’ says Nobre. The big question is how our brain manages this. Nobre is trying to unravel this step by step with experiments in which study participants perform specific tasks while their brain activity is measured.
Anticipation is an important part of her research. Instead of letting all the information flow in and checking for relevance, your brain proactively focuses your attention on something. Early research considered how the brain focusses on specific places in the world around you – so-called spatial attention. In the 1990s, Nobre and colleagues described a network of brain regions involved in controlling spatial attention in the human brain. In addition to spatial attention, your brain can also focus your attention selectively on specific moments in time. Nobre and her colleagues were the first to study this capacity in the human brain. ‘The most important finding is a fairly simple observation,’ says Nobre. ‘The brain can anticipate and prioritise a sensory stimulus based on its timing.’
Nobre studies this so-called temporal attention with experiments in which she gives people simple tasks while studying their brain activity. The study participants are shown various pictures and are asked questions about one of the pictures afterwards. ‘We sometimes tell people in advance when the picture we are going to ask them about will appear. Sometimes we don’t tell them, and sometimes we give them the wrong information,’ says Nobre. If people know in advance which picture they should focus on, they can answer the questions better afterwards. This is partly because your brain prepares itself when you expect a specific event, so you absorb the information better. These preparatory signals can be seen when you measure people’s brain activity. ‘If you know the timing of the event, then preparation is optimal at that precise moment.’
Attention is not only focused on the outside world. Most attention researchers investigate how the brain prepares for information coming in through the senses. However, Nobre showed that in order to perform tasks, it is also very important to focus your attention on specific items in your working memory. The working memory contains information that we actively keep available in our brains. Nobre was the first to develop experimental studies to examine this, and she has identified the network of brain areas involved, as well as relevant brain signals. Here, too, temporal attention plays a role – your brain can ensure that information from your memory is available at exactly the right moment to guide your behaviour. Nobre’s research has transformed working memory from a fixed and rigid repository into a flexible and dynamic system for bridging sensory experience, goals, and actions.
Nobre uses various technologies to visualise the brain and measure brain activity. She was among the first to use several revolutionary technologies. For example, early in her career she measured brain activity from electrodes placed within the brain. This was possible because she worked with epilepsy patients who had been implanted with these electrodes because medication was unsuccessful. ‘We could measure human brain activity directly,’ says Nobre. ‘That in itself was extraordinary. But we also made an amazing discovery: when we showed people words, brain areas reacted that were way outside the known language network. It was completely different from anything in the textbooks. But it was so tangible and real, you could see the response in the brain immediately. It was an incredible thrill to discover something completely unexpected.’ Nobre’s discoveries in this area were major breakthroughs in understanding the language network in the human brain.
A full understanding of the human brain requires measuring brain activity systematically, in healthy people performing different types of tasks. For this, you want to measure brain activity in a harmless way from outside the brain. Nobre has been a major figure in using and advancing methods for recording and analysing signals from the scalp to understand cognition. She was also a pioneer in using functional MRI to image brain activity. fMRI can map out which brain areas are active by detecting the oxygen-rich blood flowing to these areas.
Sometimes large scanners are not even necessary: Nobre has recently developed new methods of tracking where a person’s attention is focused in their mind just by measuring changes to the eyes. For example, she and her colleagues could tell by measuring tiny involuntary eye movements if someone was focusing on a picture to the left or right of the grid they were holding in memory. Even the pupil diameter can be telling. Nobre showed, for example, that people’s pupils become smaller or larger when they focus on a light or dark item held in mind. ‘So, we can actually read things about the human mind just by looking at the outside, at the face.’
Alzheimer’s and Parkinson’s
Nobre uses the knowledge she gains about the brain to research what happens in the case of neurodegenerative diseases such as Alzheimer’s and Parkinson’s. ‘Brain imaging tends to be the standard go-to method in clinical human neuroscience,’ says Nobre. ‘For example, in Alzheimer’s disease, researchers look at the reduction of tissue in the hippocampus and related areas, or they use positron emission tomography (PET) to look for specific molecules that are characteristic of degenerative processes. However, by the time structural changes are visible, it is already late in the degenerative process. We want to develop much earlier, sensitive markers of disease risk and onset. That is why we are exploring the promise of brain recording methods like magnetoencephalography and electroencephalography, better known as MEG and EEG. These allow us to measure the actual brain activity in real time. We can get readouts of how well functional networks are performing, like subtle changes to their dynamics or rhythms, and detect if the system is not working optimally at a much earlier stage.’ Nobre compares this to an athlete who develops an injury. It is much better to detect small changes in their running rhythm or movement early on, rather than noticing it when they are in too much pain to run.
The collection of brainwaves, measured using sensors in different locations, appears as a series of squiggly lines on Nobre’s computer screen. Nobre looks at different aspects of this brain activity. ‘Some brain networks have characteristic rhythms,’ she says. ‘This is the case, for example, with the motor system, which controls movement. We are trying to see if changes take place in those rhythms.’ Nobre also takes series of snapshots of so-called brain states, taking a photo, as it were, of briefly held stable patterns of activity, like poses, the brain takes. These basic states reveal something about what the brain is working on at that moment. ‘So, you say, for example, the brain is in the so-called beta state for 20 milliseconds, and then it goes to another state for 100 milliseconds, and then it comes back again,’ Nobre explains. ‘You can then see whether a brain network has been active for too long, or not long enough. Or perhaps the period of time between two states is too long.’ This research is still in its early stages, but Nobre has already found differences in brain activity in the motor systems between people with Parkinson’s and healthy people. ‘I think these little squiggles will reveal a lot more as we learn to understand their language better.’
Kia Nobre (Rio de Janeiro, 1963) grew up in Rio de Janeiro and studied neuroscience at Williams College in Williamstown. In 1993, she received her PhD in neuroscience from Yale University. After a postdoc at Yale and a research position at Harvard Medical School, she moved to the United Kingdom in 1994. She became a faculty member of the Department of Experimental Psychology and a tutorial fellow at the University of Oxford, and was promoted to professor of Cognitive Neuroscience in 2006. Since 2010, she has been director of the Oxford Centre for Human Brain Activity. In 2014, she became the first Chair of Translational Cognitive Neuroscience. Nobre is a member of the British Academy, Academia Europaea, and National Academy of Sciences in the USA. In addition to the C.L. de Carvalho-Heineken Prize for Cognitive Science, awards she has received include the MRC Suffrage Science Award, the Broadbent Prize, and the APS Mentor Award.
Kia Nobre studies how our brain combines signals from our environment and our memory to shape experiences. Among other things, she focuses on how our brain can concentrate on the most relevant signals from the environment and the relevant items in our short-term memory. She also studies how different areas of the brain communicate with each other, and how this brain activity is coordinated. Nobre uses various technologies to visualise the brain and measure brain activity while study participants perform tasks. She is also developing methods to detect neurodegenerative diseases at an early stage.
Every two years, Heineken Prizes are awarded to five renowned international scientists and one artist. In 1964, Alfred Heineken established the Dr H.P. Heineken Prize for Biochemistry and Biophysics as a tribute to his father. Later, Heineken Prizes for the Arts, Medicine, Environmental Sciences, Historical Sciences, and Cognitive Sciences followed.