Movies and books featuring dissociative characters, like Split or the Strange Case of Dr Jekyll and Mr Hyde, succeed commercially but fail in the accurate representation of dissociative disorders. Nonetheless, their success and popularity underlie the public zeitgeist surround dissociation and how it relates to our experience of consciousness. Like other mental health disorders, those suffering from dissociation face stigma in their everyday lives.
To start off, what exactly is a state of dissociation?
During states of dissociation, we temporarily detach from consciousness and our normal cognitive processes. Our emotions or sense-of-self become removed from the perception of our own body.
During absence seizures, individuals may temporarily stare off into space, losing awareness of the outside world for a short period of time. This is especially common in children, leading to learning, social and behavioural challenges.
Individuals may also develop an altered state of consciousness after traumatic experiences, leading to temporary dissociative states. Dissociation is experienced in schizophrenia and dissociative identity disorder. People report voices representing distinct personalities as well as memory loss, among other symptoms.
Ketamine is a drug that also induces these altered states of consciousness. It is a dissociative anesthetic drug, that may also treat some forms of depression. Ketamine and other dissociative drugs are also used recreationally for these effects.
Despite the prevalence of dissociation across many neuropsychiatric and stress-related disorders, we still don’t know much about this cognitive state.
New Insights into Dissociation
Crucially, understanding dissociation will help us understand and treat many neuropsychiatric disorders while bringing us closer to understanding consciousness. A study recently published in Nature on September 16th, 2020 identifies brain rhythms or electrical signals associated with the dissociative state. Understanding the underlying mechanisms may prove fundamental in deciphering complex cognitive states.
Researchers recorded brain activity in mice after ketamine administration. To determine whether this effect resulted from the administration of all anesthetic drugs, authors also tested drugs that don’t induce a dissociative state. To ensure observed phenomenon are not just ketamine-specific, other dissociative anesthetics were also tested.
If ketamine and other dissociative anesthetics shared a unique signature somewhere in the brain, it would provide us with an idea of the mechanisms behind dissociation.
Incredibly, a neural rhythm in one part of the brain emerged only in mice treated with dissociative drugs. This rhythm began within 120 seconds, lasting 45 minutes.
The region of the brain producing these oscillations was the retrosplenial cortex. This brain region is crucial for cognition, navigation, and episodic memories. Cells located in the fifth layer of the cortex, normally connected with the rest of the brain, generated low-frequency neural activity during dissociation. Other parts of the brain became disconnected from the retrosplenial cortex during this dissociation.
After discovering these rhythms, researchers asked if they correlated with dissociative behaviors. While there’s no way to determine whether mice are experiencing symptoms of dissociation, researchers tested to see if they remained aware of their surroundings. By exposing the mouse to an aversive stimulus, researchers checked to see if it reacted. If mice didn’t react, they were likely experiencing a dissociative state.
Remarkably, these rhythms associated with this measure of dissociative-like behavior.
Will activating these brain cells cause dissociation?
At this point in their study, it’s still unclear whether these brain cells are responsible for dissociation. They might be a signature or an epiphenomenon of dissociation. Researchers modified retrosplenial cortex cells so that they would activate in response to specific wavelengths of light.
Shining light would activate the cell, causing it to fire. This technology acts as a light-switch, allowing for careful, specific dissection of neural networks. If these brain signals are behind the sense of dissociation, mice would enter this state upon activation. Indeed, turning on these cells to start this enigmatic rhythm lead to mice entering a dissociative-like state.
Researchers also measured these rhythms in the brain of an epileptic individual. In a previous surgery, electrodes were implanted. These electrodes provided researchers into the brain of this person. Before seizures, people with epilepsy often experience an aura or a dissociative feeling. While this individual experienced this aura, researchers saw that the retrosplenial cortex of the brain was generating these same rhythms.
“I was listening to two parts of my brain speak to each other in a way that a third part of my brain, which I considered to be me, was able to listen.
What would it feel like if someone else were to come into your head? What I considered me shrank to this other part of me where the other parts of my brain were talking. I stopped considering them.”
It’s often challenging to test these hypotheses in humans as implanted electrodes are needed to measure these rhythms. Additionally, our understanding of dissociation relies on collating individual experiences. Dissociation manifests in different ways for different people, further confounding human research. Part of the value in these rhythms lies in developing procedures to induce anesthetic states, without the side-effects.
The emergence of better technologies for monitoring and interfacing with the brain provides unparalleled insights into its function. Additionally, the number of generous individuals that volunteer themselves for these studies is invaluable. A few weeks ago, another intriguing paper linked a degenerating region in a man’s brain with reading and understanding numbers. Curiously losing the ability to understand or read the numbers 2–9, he could still read letters. It is another intriguing case where we aren’t able to perceive certain aspects of our reality.