The brain on alert
When focussing attention, the neurotransmitters noradrenaline and acetylcholine play an important role. This new finding made by psychologist Stephen Brown provides clues for further research on how focussed attention comes about. Dissertation defence on 16 June.
Until the mid-90s it was thought that noradrenaline was mainly important for the sleep cycle and attentiveness. Brown found indications that this neurotransmitter, which is produced in the brain, is also essential for focussed attention. ‘The more active the parts of the brain are that supply the brain with noradrenaline, the better you can focus your attention on important stimuli that you need to react to. Such as a car approaching you while you’re crossing the street, for example.’ Brown found an additional substance that plays a role in focussed attention: acetylcholine. ‘My research shows that you can’t say: this substance is the one that regulates attention. There are various substances involved’, says Brown.
Brown conducted a well-known test on test subjects in which they are presented with a series of letters in quick succession. Suddenly two numerals appear between the letters presented at intervals of less than half a second. What is striking is that people see the first numeral—indicating that they do have ‘focused attention’ for that—but they don’t see the second one. This phenomenon was called ‘attentional blink’. Brown explains, ‘The cells in areas of the brain where noradrenaline is produced probably need to recover. They need to recuperate from noticing the first number. This causes test subjects to overlook the second number.’
In order to investigate how this ‘attentional blink’ works in the brain, Brown made the loci coerulei—the cerebral nuclei that supply the brain with noradrenaline—less active. He did this by administering the drug clonidine to the test subjects. He then looked at their brains with an EEG scan while they were performing the ‘attentional blink’ test. ‘We saw peaks which we suspected reflected the focussing of attention, among other things’, the psychologist continues. ‘These peaks were smaller in individuals who received clonidine than those who got a placebo. Reduced activity of the loci coeruli makes it more difficult to focus one’s attention efficiently. That is an indication that noradrenaline stimulates attentiveness.’
Attention is not regulated only by noradrenaline, according to Brown. In another experiment he discovered that the neurotransmitter acetylcholine also improves focussed attention. ‘Higher cognitive processes like focussing your attention on something are a complex story. They are not regulated by one single neurotransmitter. If you want to understand these processes you need to look a lot closer at different neurotransmitters. You have to look at the entire system.'
Dissertation defence on 16 June 2015: S.B.R.E. Brown, The role of the locus-coeruleus-noradrenaline system in temporal attention and uncertainty processing
(9 June 2015 – CR)