7th
Concentration. When Our Neurons Remain Silent So That Our Performances May Improve
(Whenever we look carefully for an object around us, the parts of the brain that are coloured in red are activated; but, at the same time, those in blue must deactivate themselves. (Credit: Image courtesy of INSERM (Institut national de la santé et de la recherche médicale)
“To be able to focus on the world, we need to turn a part of ourselves off for a short while, and this is precisely what our brain does. (…) A team of researchers from Inserm, led by Jean Philippe Lachaux and Karim Jerbi (Lyon Neuroscience Research Centre), has just demonstrated that a network of specific neurons, referred to as “default-mode network” works on a permanent basis even when we are doing nothing. (…)
They demonstrate more specifically that when we need to concentrate, this network disrupts the activation of other specialized neurons when it is not deactivated enough. (…)
When we focus on the things around us, certain parts of the brain are activated: this network, well known to neurobiologists, is called the attention network. Other parts of the brain, however, cease their activity at the same time, as if they generally prevented our attention from being focused on the outside world. These parts of the brain form a network that is extensively studied in neurobiology, and commonly known as the “default-mode network,” because, for a long time, it was believed that it activated itself when the brain had nothing in particular to do. This interpretation was refined through ten years of neuroimaging research that concluded by associating this mysterious network (“the brain’s dark energy” as it was called by one of its discoverers, Marcus Raichle) with a host of intimate and private phenomena of our mental life: self-perception, recollections, imagination, thoughts… (…)
[Researchers] has just revealed how this network interferes with our ability to pay attention, by assessing the activity of the human brain’s default-mode network neurons on a millisecond scale for the first time ever. (…)
The results unambiguously illustrate that whenever we look for an object in the area around us, the neurons of this default-mode network stop their activity. Yet, this interruption only lasts for the amount of time required to find the object: in less than a tenth of a second, after the object has been found, the default-mode network resumes its activity as before. And if our default-mode network is not sufficiently deactivated, then we will need more time to find the object.
These results show that there is fierce competition for our attentional resources inside our brain which, when they are not used to actively analyse our sensorial environment, are instantaneously redirected towards more internal mental processes. The brain hates emptiness and never stays idle, even for a tenth of a second.”
— When Our Neurons Remain Silent So That Our Performances May Improve, ScienceDaily, Nov. 3, 2011.
See also:
☞ Transient Suppression of Broadband Gamma Power in the Default-Mode Network Is Correlated with Task Complexity and Subject Performance, The Journal of Neuroscience, 12 Oct 2011.
“Task performance is associated with increased brain metabolism but also with prominent deactivation in specific brain structures known as default-mode network (DMN). (…)
We found that all DMN areas displayed transient suppressions of broadband gamma (60–140 Hz) power during performance of a visual search task and, critically, we show for the first time that the millisecond range duration and extent of the transient gamma suppressions are correlated with task complexity and subject performance. In addition, trial-by-trial correlations revealed that spatially distributed gamma power increases and decreases formed distinct anticorrelated large-scale networks.
Beyond unraveling the electrophysiological basis of DMN dynamics, our results suggest that, rather than indicating a mere switch to a global exteroceptive mode, DMN deactivation encodes the extent and efficiency of our engagement with the external world. (…)”
