Posts Tagged ‘thalamus’


A scan of the man missing 90% of his brain.

by Paul Ratner

What we think we know about our brains is nothing compared to what we don’t know. This fact is brought into focus by the medical mystery of a 44-year-old French father of two who found out one day that he had most of his brain missing. Instead his skull is mostly full of liquid, with almost no brain tissue left. He has a life-long condition known as hydrocephalus, commonly called “water on the brain” or “water head”. It happens when too much cerebrospinal fluid puts pressure on the brain and the brain’s cavities abnormally increase.

As Axel Cleeremans, a cognitive psychologist at the Université Libre in Brussels, who has lectured about this case, told CBC:

“He was living a normal life. He has a family. He works. His IQ was tested at the time of his complaint. This came out to be 84, which is slightly below the normal range … So, this person is not bright — but perfectly, socially apt”.

The complaint Cleeremans refers to is the original reason the man sought help – he had leg pain. Imagine that – you go to your doctor with a leg cramp and get told that you’re living without most of your brain.

The man continues to live a normal life, being a family man with a wife and kids, while working as a civil servant. All this while having 3 of his main brain cavities filled with only fluid and his brainstem and cerebellum stuck into a small space that they share with a cyst.

What can we learn from this rare case? As Cleeremans points out:

“One of the lessons is that plasticity is probably more pervasive than we thought it was… It is truly incredible that the brain can continue to function, more or less, within the normal range — with probably many fewer neurons than in a typical brain. Second lesson perhaps, if you’re interested in consciousness — that is the manner in which the biological activity of the brain produces awareness… One idea that I’m defending is the idea that awareness depends on the brain’s ability to learn.”

The French man’s story really challenges the idea that consciousness arises in one part of the brain only. Current theories hold that the part of the brain called the thalamus is responsible for our self-awareness. A man living with most of his brain missing does not fit neatly into such hypotheses.

http://bigthink.com/paul-ratner/the-medical-mystery-of-a-man-living-with-90-of-his-brain-missing?utm_source=Big+Think+Weekly+Newsletter+Subscribers&utm_campaign=709f2481ff-Newsletter_072016&utm_medium=email&utm_term=0_6d098f42ff-709f2481ff-41106061

by Natalie Wolchover

The main theory of psychedelics, first fleshed out by a Swiss researcher named Franz Vollenweider, is that drugs like LSD and psilocybin, the active ingredient in “magic” mushrooms, tune down the thalamus’ activity. Essentially, the thalamus on a psychedelic drug lets unprocessed information through to consciousness, like a bad email spam filter. “Colors become brighter , people see things they never noticed before and make associations that they never made before,” Sewell said.

LSD, or acid, and its mind-bending effects have been made famous by pop culture hits like “Fear and Loathing in Las Vegas,” a film about the psychedelic escapades of writer Hunter S. Thompson. Oversaturated colors, swirling walls and intense emotions all supposedly come into play when you’re tripping. But how does acid make people trip?

Life’s Little Mysteries asked Andrew Sewell, a Yale psychiatrist and one of the few U.S.-based psychedelic drug researchers, to explain why LSD short for lysergic acid diethylamide does what it does to the brain.

His explanation begins with a brief rundown of how the brain processes information under normal circumstances. It all starts in the thalamus, a node perched on top of the brain stem, right smack dab in the middle of the brain. “Most sensory impressions are routed through the thalamus, which acts as a gatekeeper, determining what’s relevant and what isn’t and deciding where the signals should go,” Sewell said.

“Consequently, your perception of the world is governed by a combination of ‘bottom-up’ processing, starting … with incoming signals, combined with ‘top-down’ processing, in which selective filters are applied by your brain to cut down the overwhelming amount of information to a more manageable and relevant subset that you can then make decisions about.

“In other words, people tend to see what they’ve been trained to see, and hear what they’ve been trained to hear.”

The main theory of psychedelics, first fleshed out by a Swiss researcher named Franz Vollenweider, is that drugs like LSD and psilocybin, the active ingredient in “magic” mushrooms, tune down the thalamus’ activity. Essentially, the thalamus on a psychedelic drug lets unprocessed information through to consciousness, like a bad email spam filter. “Colors become brighter , people see things they never noticed before and make associations that they never made before,” Sewell said.

n a recent paper advocating the revival of psychedelic drug research, psychiatrist Ben Sessa of the University of Bristol in England explained the benefits that psychedelics lend to creativity. “A particular feature of the experience is … a general increase in complexity and openness, such that the usual ego-bound restraints that allow humans to accept given pre-conceived ideas about themselves and the world around them are necessarily challenged. Another important feature is the tendency for users to assign unique and novel meanings to their experience together with an appreciation that they are part of a bigger, universal cosmic oneness.”

But according to Sewell, these unique feelings and experiences come at a price: “disorganization, and an increased likelihood of being overwhelmed.” At least until the drugs wear off, and then you’re left just trying to make sense of it all.

http://www.livescience.com/33167-how-acid-lsd-make-people-trip.html?li_source=pm&li_medium=most-popular&li_campaign=related_test