How quickly do we become conscious of signals in the environment? A new study shows that the human brain has a fundamental timescale of around 200ms where information is optimally broadcast across brain regions. The question of timescale is a fundamental question in many sciences. As an example, think of the difference between weather and climate, where some experimental data such as rain is measured on the timescale of minutes and hours, while wet seasons are measured on the timescale of months, and climate change on the timescale of decades. Thus, if we are interested in the prediction of rainfall, the relevant timescale of experimental data is over minutes and hours, while measurements taken over, say, seconds, months or years are not particularly helpful.

In the brain the fast timescale is very important for conscious information processing as proposed by Stan Dehaene and Jean-Pierre Changeux in their very influential global workspace theory. Once information enters the brain, it has quickly to be made available for many regions across the brain in order to be consciously perceived. For instance, a recent study in primates recorded from a few brain regions and found that the ignition of visual stimuli is associated with strong sustained activity in prefrontal cortex around 200-250 ms when consciously reported by the animal, while this frontal activity was weaker and quickly decayed for unreported stimuli.

“The new framework, poetically called brain songs, sheds new light on the whole-brain networks involved in broadcasting information at this fast timescale. As such it supports and extends current accounts of when information becomes consciously available in the human brain"

Now, in a technical tour-de-force, an international team of researchers have made significant advances in our understanding of the timescale activity of whole-brain dynamics, according to a study published February 4, 2019 in the high-impact journal Nature Communications, by Prof Gustavo Deco, Josefina Cruzat and Prof Morten Kringelbach from the Universities of Pompeu Fabra (Spain), Oxford (UK) and Aarhus (Denmark).

Prof Gustavo Deco, the lead author of the study says: “The new framework, poetically called brain songs, sheds new light on the whole-brain networks involved in broadcasting information at this fast timescale. As such it supports and extends current accounts of when information becomes consciously available in the human brain.”

“More generally, brain songs could be used to understand why the timescale of conscious processing changes in some diseases and as such the new findings could have important implications for understanding changes in neuropsychiatric disease – and perhaps even the nature of consciousness”, says Prof Morten Kringelbach.

Reference Work

Gustavo Deco, Josephine Cruzat, Morten Kringelbach (2019), "Brainsongs framework used for Discovering the relevant timescale of the human brain", 4 february, Nature Communications, 10, nº 583.