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“The brain is like an orchestra”

“The brain is like an orchestra”

Photographer:Fotograaf: archive Alexander Sack

Research on brain stimulation

It’s a world first: the combination of three different techniques for brain research. Alexander Sack, professor of Functional Brain Stimulation and Neurocognitive Psychology, aims to develop new brain stimulation methods to treat people with attention and memory problems following a stroke. Two weeks ago he was awarded a Vici grant for this research.

After a stroke many people suffer from an impaired memory and concentration problems. “These are two brain functions you need for almost everything”, says Sack, a neuroscientist. “For example, when you look at someone, you focus entirely on that person. You ignore other information that enters your brain, such as what else you can see in the room or what you can hear outside. The memory is hard at work too, storing what you see and what is said.” In stroke patients, something here has gone wrong – but what exactly?

It’s too simple to say that the areas in their brains dedicated to memory and attention no longer work properly. “People tend to think that every function has its own place in the brain. They picture one of those images where a certain area in the brain – the active area – is lit up in colour. But that would be very inefficient and inflexible; for that to work you’d need to have an implausibly large brain.”

In reality, the different brain areas carry out their functions by communicating with one another; that is, by sending information to one another at a certain frequency. “Every brain area is full of neurons. If an area wants to ‘talk’ the neurons transmit signals in a certain rhythm, and the receiver starts to send out the same rhythm. The brain is like an orchestra: there are many instruments but together they play the same music. These are known as brain waves and they exchange a great deal of information, even between brain areas that are far away from one another. For example, the attention and memory network encompasses a number of areas that can engage in dialogue with one another flexibly depending on the task that needs to be accomplished.”

In his research, Sack disturbs this communication in healthy test subjects by means of brain stimulation. A magnetic coil is placed on their heads, and this sends impulses into the brain. “We want to pinpoint how different brain areas and networks cooperate. Suppose I disable a certain network node – will the brain area then send that information to a different partner? And does it matter whether I do that in a peak of a brain wave or a valley? We then look at the consequences in terms of carrying out the task.”

To make this whole process run smoothly, Sack uses three different techniques: fMRI to identify the active brain areas, EEG to determine what communication is going on, and brain stimulation through the magnetic coil. “No other lab in the world is doing this.”

With the help of the Vici grant, worth €1.5 million, Sack aims to achieve two goals in the coming five years. “First, we want to understand the brain better by way of fundamental research. Second, we’re keen to improve the memory and attention performance of stroke patients. You can force a brain area to fire signals in a certain rhythm, thereby introducing a pattern into the brain. The hope is that this will help people to perform tasks more effectively. If you do it once, the effect is temporary. But if you do it every day over the course of four to six weeks, the effect is long-lasting and sometimes even permanent. This kind of treatment is already being used for people with depression.”

Sack and his colleagues have already seen some positive results. Before applying for the Vici grant, Sack conducted a pilot study among people who suffer from neglect following a stroke. This refers to the systematic neglect of either one half of the body or part of the patient’s environment; for example, they eat only half of the food on their plate or shave only half of their face. “The eyes are working just fine, but half of the information that enters through them is ignored.” In the study the test subjects were asked to look at the centre of a computer screen. Objects then appeared on the right or the left (or on both sides) of the screen, and the participants had to indicate what they saw. “On average they got 35 out of 40 answers wrong because they just don’t see one side. After brain stimulation the number of correct answers doubled, and rose further still after five minutes and after twenty minutes.”

In the coming years Sack hopes to further fine-tune brain stimulation. In the long term, this would be good news – and not only for stroke victims. “After a stroke or an accident, the area that needs rehabilitating is easier to localise, because the damage to the brain is visible. But in principle that doesn’t matter; brain stimulation could also be useful in treating other disorders where cognitive processes are disturbed, such as depression, or even in slowing down the cognitive decline caused by dementia and other diseases.”



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