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Why don’t we hallucinate more often?

#1
C C Offline
https://cosmosmagazine.com/biology/why-d...more-often

EXCERPT: . . . The findings are presented in a paper published in the journal Science. Karl Deisseroth is a leading exponent of optogenetics, a technology that allows researchers to stimulate particular neurons in freely moving animals with pulses of light, and to observe the resulting effects [...]

In their latest study [...] a specially-developed device to project holograms – three-dimensional configurations of targeted photons – onto, and into, a mouse’s visual cortex. ... When mice were shown random series of horizontal and vertical bars displayed on a screen, the researchers recorded which neurons in the exposed visual cortex were preferentially activated by one or the other orientation. From these results, they were able to identify dispersed populations of individual neurons that were "tuned" to either horizontal or vertical visual displays.

[...] the mice [were trained] to lick the end of a nearby tube for water when they saw a vertical bar but not when they saw a horizontal one or saw neither. ... The mice's performance perked up if the visual displays were supplemented with simultaneous optogenetic stimulation – but only when the stimulation was consistent with the visual stimulation...

[...Eventually...] the researchers were able to induce tube-licking behaviour simply by projecting the "vertical" holographic program onto the mice's visual cortex. But the mice wouldn't lick the tube if the "horizontal" program was projected instead. "Not only is the animal doing the same thing, but the brain is, too," Deisseroth says. "So we know we're either recreating the natural perception or creating something a whole lot like it."

"It's quite remarkable how few neurons you need to specifically stimulate in an animal to generate a perception," Deisseroth says. "A mouse brain has millions of neurons; a human brain has many billions," he adds."If just 20 or so can create a perception, then why are we not hallucinating all the time, due to spurious random activity? Our study shows that the mammalian cortex is somehow poised to be responsive to an amazingly low number of cells without causing spurious perceptions in response to noise." (MORE - details)
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#3
C C Offline
(Jul 21, 2019 02:10 PM)Zinjanthropos Wrote: https://www.sciencemag.org/news/2017/08/how-your-mind-protects-you-against-hallucinations

Expectations? 

Read your article CC and wondered if that info might help schizophrenics, found above link.

Optogenetics is being used to at least study schizophrenic brains, and could be placed in the context of deep brain stimulation in general. An implantable optogentic device without wires allows research mice to move more freely, and somewhere down the line might be recruited for potential treatment approaches, along with the continued development of conventional brain implants. Some recent neural sensors fool the brain into not rejecting them, so any future optogenetic implants adapted to be longer-lasting devices like that would be a necessary step.


Optogenetic neuronal control in schizophrenia (2011)
https://www.ncbi.nlm.nih.gov/pubmed/21482453

In recent years brain stimulation technologies have emerged in the bio-scientific scenery. Deep brain stimulation now plays an important role in the treatment of many neurological disorders, and seems promising in treating depression. Optogenetics is a new technology that offers control over neuronal activity by turning on and off distinct neuronal populations. It has a great advantage over previous brain stimulation technologies in that it is accurate and specific to the neurons intended for activation and control.


Optogenetic induction of the schizophrenia-related endophenotype of ventral hippocampal hyperactivity causes rodent correlates of positive and cognitive symptoms (2018)
https://www.nature.com/articles/s41598-018-31163-5


Free to roam: implantable optogenetic devices (2016)
https://www.nature.com/scitable/blog/bio...ptogenetic

Taking this a step further, we looked at small wires that can be implanted in the brain and are capable of optogenetic stimulation, neuronal recording, and drug delivery all in an awake and behaving mouse. As incredible as that is, and it most certainly is amazing, having a large wire implanted into a mouse brain and attached to a machine is a rather unnatural setup. It can limit the movement of the mouse, and alter its behavior. In order to fix this, scientists have been working on wireless optogenetic devices so can control neuronal activity in mice that are free to move around without having a wire attached to their head.


Bionic Implant to Treat Mental Disorders in Development
https://www.iflscience.com/brain/bionic-...velopment/

Scientists are developing the first bionic implant that will help treat mental disorders. Over the next three years Professor Xu-Feng Huang and his researchers from the University of Wollongong in Australia will lead the development of a bionic implant which will mitigate the symptoms of schizophrenia.


Sensors go undercover to outsmart the brain (2019)
https://news.harvard.edu/gazette/story/2...l-illness/

Lke a well-guarded fortress, the human brain attacks intruders on sight. Foreign objects, including neural probes used to study and treat the brain, do not last long. But now, researchers have designed a probe that looks, acts, and feels so much like a real neuron that the brain cannot identify it as an imposter. [...] Though further research is needed, the neuron-like electronics could eventually offer a safe, stable alternative to treat neurological diseases, brain damage, and even depression and schizophrenia, where they can provide the added benefit of actively monitoring and modulating regenerated neural networks.
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#4
Secular Sanity Offline
I've been reading up on hallucinogens due to Syne's induced feelings of transcendence. You know, his big claim to fame.  Big Grin

It is fascinating but I wouldn't want to mess with it. I enjoy having physical boundaries. I like knowing where I end and the world begins. Losing yourself doesn't sound too appealing to me but it might help us develop better treatments for schizophrenia.

Researchers are investigating how hallucinogens might be used to model—and develop treatments for—psychosis

LSD, “magic” mushrooms and mescaline have been banned in the U.S. and many other countries since the 1970s, but psychedelic medicine is making a comeback as new therapies for depression, nicotine addiction and anxiety. The drugs have another scientific use, too: so-called psychotomimetics, or mimics of psychosis, may be useful tools for studying schizophrenia. By creating a brief bout of psychosis in a healthy brain, as indigenous healers have for millennia, scientists are seeking new ways to study—and perhaps treat—mental illness.

“We think that schizophrenia is a group of psychoses, which may have different causes,” says Franz Vollenweider, a psychiatrist and neuroscientist at the University of Zurich. “The new approach is to try to understand specific symptoms: hearing voices, cognitive problems, or apathy and social disengagement. If you can identify the neural bases of these, you can tailor the pharmacology.”

The World’s Fist Images of the Brain on LSD
The findings show how the drug decreases communication between the brain regions that make up the Default Mode Network . The DMN polices the amount of sensory information that enters our sphere of awareness, and has been described as the neural correlate of the ‘ego’.

Yet the DMN disintegrates under LSD, allowing for a magnificent increase in communication between brain networks that are normally highly segregated. This produces a more integrated pattern of connectivity throughout the entire brain, which may be associated with more fluid modes of cognition. Results of the study show that the magnitude of this effect is directly correlated to the strength of the subjective experience of ‘ego-dissolution’ and feeling of oneness and unity.

The resulting images showed how the brain’s visual cortex, which normally receives and processes information from the eyes, begins to communicate with a wide range of other brain regions under the effects of LSD. This means that many brain regions that aren’t normally involved in vision suddenly contribute to visual processing, which explains why people tend to experience dreamlike hallucinations when they use the drug.

“We observed brain changes under LSD that suggested our volunteers were ‘seeing with their eyes shut’ – albeit they were seeing things from their imagination rather than from the outside world.  We saw that many more areas of the brain than normal were contributing to visual processing under LSD – even though the volunteers’ eyes were closed.

Interestingly, though, the studies on the effects of hallucinogens on blind people showed that the ones that were born blind or became blind at a very early age didn’t experience visual hallucinations.

Here’s a case report...
This case report offers rare insights into crossmodal responses to psychedelic drug use in a congenitally blind (CB) individual as a form of synthetic synesthesia. BP's personal experience provides us with a unique report on the psychological and sensory alterations induced by hallucinogenic drugs, including an account of the absence of visual hallucinations, and a compelling look at the relationship between LSD induced synesthesia and crossmodal correspondences. The hallucinatory experiences reported by BP are of particular interest in light of the observation that rates of psychosis within the CB population are extremely low. The phenomenology of the induced hallucinations suggests that experiences acquired through other means, might not give rise to “visual” experiences in the phenomenological sense, but instead gives rise to novel experiences in the other functioning senses.

“In this paper, we provide a detailed insight into synesthetic hallucinations as a response to psychedelic drug use in a CB [congentially blind] ex-rock music singer (or ‘rock star’ by his own account) identified by the pseudonym Mr. Blue Pentagon (BP). BP’s personal experience provides us with a unique report on the psychological and sensorial alterations induced by hallucinogenic drugs, including an account on the absence of visual hallucinations, and a compelling look at the relationship between LSD induced synesthesia and cross-modal correspondences.”

“Every time I did acid, I experienced something new and spectacular,” he reported. “Obviously through the senses which are available to me! I never had any visual images come to me. I can’t see or imagine what light or dark might look like.

What’s even more interesting is that being born blind protects people from developing schizophrenia. A large scale study that showed no incidents of schizophrenia in cortically blind people have ever been recorded to date.

Congenital blindness is protective for schizophrenia and other psychotic illness. A whole-population study.
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#5
Yazata Offline
(Jul 21, 2019 03:30 AM)C C Wrote: Why don't we hallucinate more often?

What do you mean "we"? Big Grin

It is an interesting question though. If a relatively small amount of stimulation of the visual cortex can produce visual experience, why isn't constant noise in the neural system producing it all the time?

My own speculation is that there's a noise-suppression filter at work in there.

I used to use LSD quite a bit, back in the day, and the most common kind of (pseudo)hallucination that I'd experience would be LSD's familiar patterns. These were a chaotic profusion of surfaces, edges, curves and corners, all in the most vivid colors, filling the visual field, but somehow never really obscuring actual vision either. It was more like it was superimposed upon it. Everything I looked at seemed to be covered with... glowing, incandescent writing... in some incomprehensible language. I used to feel like if I could somehow read it, the secrets of the universe would be revealed.

And my theory is that all the corners, edges, colors and curves were basically just feature-detectors in the visual system being triggered off by noise. LSD had seemingly disabled the filter that screens it out of conscious awareness.

How the brain distinguishes signal from noise is an interesting (and profound) question.
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#6
Syne Offline
(Jul 21, 2019 07:09 PM)Yazata Wrote:
(Jul 21, 2019 03:30 AM)C C Wrote: Why don't we hallucinate more often?

What do you mean "we"? Big Grin

It is an interesting question though. If a relatively small amount of stimulation of the visual cortex can produce visual experience, why isn't constant noise in the neural system producing it all the time?

My own speculation is that there's a noise-suppression filter at work in there.

I used to use LSD quite a bit, back in the day, and the most common kind of (pseudo)hallucination that I'd experience would be LSD's familiar patterns. These were a chaotic profusion of surfaces, edges, curves and corners, all in the most vivid colors, filling the visual field, but somehow never really obscuring actual vision either. It was more like it was superimposed upon it. Everything I looked at seemed to be covered with... glowing, incandescent writing... in some incomprehensible language. I used to feel like if I could somehow read it, the secrets of the universe would be revealed.

And my theory is that all the corners, edges, colors and curves were basically just feature-detectors in the visual system being triggered off by noise. LSD had seemingly disabled the filter that screens it out of conscious awareness.

How the brain distinguishes signal from noise is an interesting (and profound) question.

I've always assumed that those common LSD visuals where more of an interpreter issue than a filter issue. Considering that the brain constructs a large majority of our visual experience from relatively little stimulus input (especially considering the lack of discernible signal delay in our perceptions), I tend to think that it's not so much about noise as it is about that brain's constructive assumptions becoming much more active...constructing large amounts of details where little actually exists. I wonder if infant vision is plagued by an overly assumptive brain, until differentiation is developed. If so, I might be scared of seeming innocuous things too (bad trip, man).
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#7
C C Offline
(Jul 21, 2019 06:34 PM)Secular Sanity Wrote: . . . What’s even more interesting is that being born blind protects people from developing schizophrenia. A large scale study that showed no incidents of schizophrenia in cortically blind people have ever been recorded to date.

Congenital blindness is protective for schizophrenia and other psychotic illness. A whole-population study.


Supposedly a good chunk of the hallucinations tend to be auditory, so that's interesting, SS.

Didn't expect one of the past explanations (proposed even prior that Dec 2018 study) to roundaboutly be flirting with simulation of autism characteristics. "Indeed, anything that can push the balance in the autistic direction will suffice to counter psychotic tendencies, and [congenital and] early-onset blindness certainly appears to do so where providing protection from schizophrenia is concerned—just as the diametric model predicts!"

Quote:. . . “We observed brain changes under LSD that suggested our volunteers were ‘seeing with their eyes shut’ – albeit they were seeing things from their imagination rather than from the outside world.  We saw that many more areas of the brain than normal were contributing to visual processing under LSD – even though the volunteers’ eyes were closed."

Interestingly, though, the studies on the effects of hallucinogens on blind people showed that the ones that were born blind or became blind at a very early age didn’t experience visual hallucinations.

Here’s a case report... [...] “Every time I did acid, I experienced something new and spectacular,” he reported. “Obviously through the senses which are available to me! I never had any visual images come to me. I can’t see or imagine what light or dark might look like."

Which raises the question of how the subjects would know or not know for certain that they were experiencing visual mode events -- what would prevent them from being classed in that generic "novel experiences" category if gone unrecognized as such.

In a different research context but similar outcome for those not born blind, a synesthesia study done circa 14 years ago on non-congenital blind people did have them reporting visual crossovers. But that could have been as much due to having visual memories to recruit hallucinations from as the being able distinguish what visual experiences were due to early childhood recollections of such. (Or both combined).
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