Chapter 4. Development of the Brain

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Ken Solt & Oluwaseun Akeju The state of dissociation is commonly described as feeling detached from reality or having an ‘out of body’ experience. This altered state of consciousness is often reported by people who have psychiatric disorders arising from devastating trauma or abuse. It is also evoked by a class of anaesthetic drug, and can occur in epilepsy. The neurological basis of dissociation has been a mystery, but writing in Nature, Vesuna et al.1 describe a localized brain rhythm that underlies this state. Their findings will have far-reaching implications for neuroscience. The authors first recorded brain-wide neuronal activity in mice using a technique called widefield calcium imaging. They studied changes in these brain rhythms in response to a range of drugs that have sedative, anaesthetic or hallucinogenic properties, including three that induce dissociation — ketamine, phencyclidine (PCP) and dizocilpine (MK801). Only the dissociative drugs produced robust oscillations in neuronal activity in a brain region called the retrosplenial cortex. This region is essential for various cognitive functions, including episodic memory and navigation2. The oscillations occurred at a low frequency, of about 1–3 hertz. By contrast, non-dissociative drugs such as the anaesthetic propofol and the hallucinogen lysergic acid diethylamide (LSD) did not trigger this rhythmic retrosplenial activity. Vesuna et al. examined the active cells in more detail using a high-resolution approach called two-photon imaging. This analysis revealed that the oscillations were restricted to cells in layer 5 of the retrosplenial cortex. The authors then recorded neuronal activity across multiple brain regions. Normally, other parts of the cortex and subcortex are functionally connected to neuronal activity in the retrosplenial cortex; however, ketamine caused a disconnect, such that many of these brain regions no longer communicated with the retrosplenial cortex. © 2020 Springer Nature Limited

Keyword: Drug Abuse; Consciousness
Link ID: 27481 - Posted: 09.19.2020

Jon Hamilton Scientists used light to control the firing of specific cells to artificially create a rhythm in the brain that acted like the drug ketamine enjoynz/Getty Images Out-of-body experiences are all about rhythm, a team reported Wednesday in the journal Nature. In mice and one person, scientists were able to reproduce the altered state often associated with ketamine by inducing certain brain cells to fire together in a slow, rhythmic fashion. "There was a rhythm that appeared, and it was an oscillation that appeared only when the patient was dissociating," says Dr. Karl Deisseroth, a psychiatrist and neuroscientist at Stanford University. Dissociation is a brain state in which a person feels separated from their own thoughts, feelings and body. It is common in people who have some mental illnesses or who have experienced a traumatic event. It can also be induced by certain drugs, including ketamine and PCP (angel dust). The study linking dissociation to brain rhythms represents "a big leap forward in understanding how these drugs produce this unique state," says Dr. Ken Solt, an anesthesiologist at Harvard Medical School and Massachusetts General Hospital. Solt is the co-author of an article that accompanied the study but was not involved in the research. The finding also could be a step toward finding non-drug methods to control states of consciousness, Solt says. Deisseroth's lab made the discovery while studying the brains of mice that had been given ketamine or other drugs that cause dissociation. The team was using technology that allowed them to monitor the activity of cells throughout the brain. © 2020 npr

Keyword: Drug Abuse; Consciousness
Link ID: 27480 - Posted: 09.19.2020

By John Horgan I interviewed psychologist Susan Blackmore 20 years ago while doing research for my book Rational Mysticism. Here, lightly edited, is my description of her: “Her hair was dyed orange, red, and yellow, dark-rooted, cut short as a boy’s, with sideburns plunging like daggers past each multi-ringed ear. Words spewed from her pell-mell, accompanied by equally vigorous hand signals and facial expressions. She was keen on onomatopoeic sound effects: Ahhhhh (to express her pleasure at finding other smart people when she entered Oxford); DUN da la DUN da la DUN (the galloping noise she heard as she sped down a tree-lined tunnel in her first out-of-body experience); Zzzzzzt (the sound of reality dissolving after her second toke of the psychedelic dimethyltryptamine). We were talking in the dining room of the inn where she was staying, and twice we had to move to a quieter spot when employees or patrons of the inn started talking near us. One side effect of her spiritual practice, she explained, is that she has a hard time ignoring stimuli. ‘I think it is one of the bad effects of practicing mindfulness. I'm so aware of everything all the time.’” Blackmore began her career as a parapsychologist, intent on finding evidence for astral projection and extrasensory perception. Her investigations transformed her into a materialist and Darwinian (one of her best-known books describes humans as “meme machines”) who doesn’t believe in ESP, God or free will. And yet she is a mystic, too, who explores consciousness via meditation and psychedelics. In other words, Blackmore pulls off the trick of being both a hard-nosed skeptic and an open-minded adventurer. What more can one ask of a mind scientist? Curious about how her thinking has evolved in our mind-boggling era, I e-mailed her a few questions. An edited transcript of the interview follows. © 2020 Scientific American

Keyword: Consciousness; Drug Abuse
Link ID: 27475 - Posted: 09.16.2020