Science may have found the origin of altered states of consciousness

Scientists studying consciousness and its possible origin in the human brain may have discovered yet another area responsible for wakefulness — it is the brain stem, a region with nerve cells gathered in a thick cord at the back of the organ.

The research is linked to the understanding of altered states of consciousness, such as coma and the vegetative state, for example. Some individuals, for example, show vague perception, awareness of their surroundings or even fully wake up during anesthesia, something that science still does not understand very well.

States of consciousness and the brain

According to the still superficial scientific knowledge about consciousness, it is divided between two different dimensions: excitement — or wakefulness — and apprehension — or perception. In 2016, scientists at Harvard Medical School discovered the first evidence that the brainstem regulates arousal and parts of the brain linked to consciousness.

In patients hospitalized with brainstem injuries, the majority of unconscious patients had damage to a part of the trunk called the rostral dorsolateral pontine tegmentum, while only one of the conscious patients had damage to this region. In comatose and vegetative state patients, the connection between the brain stem and two cortical regions was also noticed in brain scans.

One of the study scientists, Brian Edlow, investigated the situation in depth in a new study with his team at the Massachusetts Institute of Technology (MIT) and the University of Tours. The mapping of neural networks in the brain blocked, unlike studies of the cortex, the external part of the organ.

This happened, in part, because imaging techniques cannot separate the activity of isolated neurons in the brain stem from the activity of networks that come from it towards the brain.

The focus was on detecting wakefulness during rest, when the brain is in “standby mode”, that is, it can process information, but is not able to dedicate itself to tasks or pay full attention. The network that comes out of the trunk was given the name “Ascending Excitation Network” (REA) by scientists, and its connection to the brain’s wakefulness centers was studied.

Such connections have already been extensively mapped in animals, but not in humans. To do this, three dead brains were examined via magnetic resonance imaging, as well as those of 84 healthy people, with data collected by the Human Connectome Project, an American initiative that plans to map connections throughout the organ.

Thus, a highly connected network was found in the midbrain, starting in the ventral tegmental area and connecting to other previously mapped points of the REA. A connection between this network and others also related to parts of the cortex that we know are responsible for consciousness was also noted.

Previously, it was thought that the ventral tegmental area was only responsible for modulating behavior and cognition, two very active processes, but the present study has increased scientific knowledge about its role in wakefulness.

Other direct connections were seen linking the cerebral trunk and cortex in the region of the medial forebrain fasciculus, which is in the frontal lobe of the organ. The study, although small, as scientists admit, is an important first step towards understanding something as vague and complex to understand as consciousness.

Source: Science Translational Medicine

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