Researchers have discovered a particular network of brain connections that may be responsible for generating the ineffable experience we call consciousness. Though it’s hard to pin down exactly what it means to be conscious, scientists are in agreement that arousal and awareness are two of its fundamental ingredients, and this latest research – which appears in the journal Neurology – provides new insights into the neural source of both of these components.
Arousal, which refers to a state of wakefulness, is thought to be controlled by the brainstem, while awareness, or the ability to experience and reflect on ourselves, is strongly associated with the cortex, where many of the brain’s higher functions are coordinated.
The team scanned the brains of 36 patients with brainstem injuries, 12 of which were in a coma while 24 were not. Of the dozen that had lost consciousness, 10 had lesions in a particular part of the brainstem called the rostral dorsolateral pontine tegmentum. In contrast, only one of the patients that was not in a coma had damage to this region, suggesting that it may play an important role in arousal.
Next, the researchers used a map of all the connections in the human brain – known as the Human Connectome – to investigate how the rostral dorsolateral pontine tegmentum is wired up to the cortex. They discovered that it is strongly connected to two cortical regions known as the anterior insula (AI) and the pregenual anterior cingulate cortex (pACC), both of which have been implicated in awareness in previous studies.
They then used MRI to scan the brains of a separate group of people with disorders of consciousness, and found that those who were in a coma tended to have major disconnections between the rostral dorsolateral pontine tegmentum and both the AI and the pACC. Crucially, this network was less disrupted in those that were not in a coma, suggesting that it may be the source of consciousness, regulating both arousal and awareness.
Understanding this mechanism could one day lead to new treatments for disorders of consciousness. For example, neuroscientists may try to artificially stimulate activity in this network in order to wake people from comas.