neurosciences

The Knight Antonius Block: I want knowledge!…

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Study provides insight into the neurobiology of dying. Investigators performed continuous patient monitoring following Do Not Resuscitate - Comfort Care orders in patients with devastating brain injury to investigate the mechanisms and timing of events in the brain and the circulation during the dying process.

{ ScienceDaily | Continue reading }

Oxygen deprivation results in brain injury. For years, researchers have been studying the underlying processes in animals: within 20 to 40 seconds, the brain enters an ‘energy-saving mode’ - it becomes electrically inactive, and all interneuronal communication ceases. Within a few minutes, the brain’s fuel reserves have become depleted that maintain the uneven distribution of ions between the inside and outside of nerve cells, and the ion gradients start to break down. This breakdown takes the form of a massive wave of electrochemical energy release in the form of heat, which is known as ’spreading depolarization’. More vividly described as a ‘brain tsunami’, this energy loss spreads through the cortex and other areas of the brain, triggering pathophysiological cascades which gradually poison the nerve cells. Importantly, this wave remains reversible up to a certain point in time: nerve cells will recover fully if circulation is restored before this point is reached. However, if circulation remains disrupted, the cells will die. Until now, recordings of electrical brain activity obtained from human subjects have been of limited applicability, and experts have been divided as to the transferability of results from animal-based research. […]

“We were able to show that terminal spreading depolarization is similar in humans and animals. Unfortunately, the research community has been ignoring this essential process of central nervous system injury for decades, all because of the mistaken assumption that it does not occur in humans,” explains Prof. Dreier.

{ EurekAlert | Continue reading }

paint on plaster { Eduardo Paolozzi, Targets, 1948 }

“Bergman burned down our home,” said Eric W. Ohlsson, a retired doctor, referring to a scene from the 1968 film “Shame,” in which a barn was used as a flaming prop

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Try this experiment: Pick a famous movie—Casablanca, say—and summarize the plot in one sentence. Is that plot you just described the thing you remember most about it? Doubtful. Narrative is a necessary cement, but it disappears from memory.

{ Peter Greenaway | Continue reading }

“I almost always remember where I was and I remember the book itself. I remember the physical object,” says Paul, the editor of The New York Times Book Review, who reads, it is fair to say, a lot of books. “I remember the edition; I remember the cover; I usually remember where I bought it, or who gave it to me. What I don’t remember—and it’s terrible—is everything else.” […] “Memory generally has a very intrinsic limitation,” says Faria Sana, an assistant professor of psychology at Athabasca University, in Canada. “It’s essentially a bottleneck.” The “forgetting curve,” as it’s called, is steepest during the first 24 hours after you learn something. Exactly how much you forget, percentage-wise, varies, but unless you review the material, much of it slips down the drain after the first day, with more to follow in the days after, leaving you with a fraction of what you took in.

{ The Atlantic | Continue reading }

‘If we can’t fix it, it ain’t broke.’ –Lieutenant Colonel Walt Weir

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Human memory systems are subject to many imperfections, including memory distortions and the creation of false memories. Here, we demonstrate a case where memory distortion is adaptive, increasing the overall accuracy of memories. […]

Although participants’ memories were systematically distorted, they were distorted in a way that is consistent with minimizing their average error […]

Thus, memory distortion may not always be maladaptive: in some cases, distortion can result from a memory system that optimally combines information in the service of the broader goals of the person. Furthermore, this framework for thinking about memory distortion suggests that false memory can be thought of on a continuum with true memory: the greater uncertainty participants have about an individual item memory, the more they weight their gist memory [Gist traces are fuzzy representations of a past event]; with no item information, they weight only their gist memory.

{ PsyArXiv | Continue reading }

photo { Ana Mendieta, Untitled, from Silueta Series, Iowa, 1978 }

On his wise shoulders through the checkerwork of leaves the sun flung spangles, dancing coins

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Two theoretical frameworks have been proposed to account for the representation of truth and falsity in human memory: the Cartesian model and the Spinozan model. Both models presume that during information processing a mental representation of the information is stored along with a tag indicating its truth value. However, the two models disagree on the nature of these tags. According to the Cartesian model, true information receives a “true” tag and false information receives a “false” tag. In contrast, the Spinozan model claims that only false information receives a “false” tag, whereas untagged information is automatically accepted as true. […]

The results of both experiments clearly contradict the Spinozan model but can be explained in terms of the Cartesian model.

{ Memory & Cognition | PDF }

art { Richard Long, Dusty Boots Line, The Sahara, 1988 }

What then can Kant mean by his mysterious suggestion that ‘objects must conform to our cognition’?

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The image of the world that we see is continuously deformed and fragmented by foreshortenings, partial overlapping, and so on, and must be constantly reassembled and interpreted; otherwise, it could change so much that we would hardly recognize it. Since pleasure has been found to be involved in visual and cognitive information processing, the possibility is considered that anhedonia (the reduction of the ability to feel pleasure) might interfere with the correct reconstruction and interpretation of the image of the environment and alter its appearance.

{ Schizophrenia Research and Treatment | Continue reading }

‘A noir, E blanc, I rouge, U vert, O bleu’ –Arthur Rimbaud

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Grapheme-color synesthesia is a neurological phenomenon in which viewing a grapheme elicits an additional, automatic, and consistent sensation of color.

Color-to-letter associations in synesthesia are interesting in their own right, but also offer an opportunity to examine relationships between visual, acoustic, and semantic aspects of language. […]

Numerous studies have reported that for English-speaking synesthetes, “A” tends to be colored red more often than predicted by chance, and several explanatory factors have been proposed that could explain this association.

Using a five-language dataset (native English, Dutch, Spanish, Japanese, and Korean speakers), we compare the predictions made by each explanatory factor, and show that only an ordinal explanation makes consistent predictions across all five languages, suggesting that the English “A” is red because the first grapheme of a synesthete’s alphabet or syllabary tends to be associated with red.

We propose that the relationship between the first grapheme and the color red is an association between an unusually-distinct ordinal position (”first”) and an unusually-distinct color (red).

{ Cortex | Continue reading }

A Black, E white, I red, U green, O blue: vowels,
Someday I shall tell of your mysterious births

{ Arthur Rimbaud | Continue reading }

art { Roland Cat, The pupils of their eyes, 1985 }

Saas and taas and specis bizaas

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Normal consciousness relies, at least in part, on the brain’s Default Mode Network (DMN), according to neuroscientist Robin Carhart-Harris, head of psychedelic research in the brain sciences division of the Imperial College of London medical school. The DMN is a network of interacting brain regions that acts as a cognitive transit hub, integrating and assimilating information. As the name implies, it’s the usual system of organization for your mind. Carhart-Harris says the DMN “gives coherence to cognition” by connecting different regions of the brain, and is considered the “orchestrator of the self.”

Carhart-Harris and his colleagues found what seems to be an important function of the DMN inadvertently. While studying brain networks, they got curious about what changes might occur when people are under the effects of hallucinogens. In studies analyzing the effects of psilocybin on brain wave oscillation and blood flow, they found that when the DMN was inactive, an alternate network of consciousness seemed to arise.

When some study subjects tested psilocybin, they reported a strong sense of interconnectedness, as well as spiritual, magical, and supernatural feelings.

In the alternate mode, brains produced a different world that offered other sensations and realizations than in everyday life. In this mode, the self wasn’t the protagonist of the narrative. Meanwhile, scans of blood flow and brain wave oscillations showed new, unusual—but orderly and synchronous—connections forming between cortical regions, as if the brain was reorganizing its network. This led Carhart-Harris to posit that the DMN generates the feeling we each have that we’re individuals, a feeling that manifests very strongly as reality. And that means we can temporarily switch off, or mute, this part of the brain.

{ Quartz | Continue reading }

According to the famous work of Roger Sperry and Michael Gazzaniga, “split brain” patients seem to experience a split in consciousness: the left and the right side of their brain can independently become aware of, and respond, to stimuli. Split brain patients are those who underwent surgery to sever the corpus callosum, the nerve tract connecting the two hemispheres of the brain.

{ Neuroskeptic | Continue reading }

art { Leah Schrager }

Real-time imitation of piano chord sequences with unexpected harmony or manner

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People’s capacity to generate creative ideas is central to technological and cultural progress. Despite advances in the neuroscience of creativity, the field lacks clarity on whether a specific neural architecture distinguishes the highly creative brain. […]

We identified a brain network associated with creative ability comprised of regions within default, salience, and executive systems—neural circuits that often work in opposition. Across four independent datasets, we show that a person’s capacity to generate original ideas can be reliably predicted from the strength of functional connectivity within this network, indicating that creative thinking ability is characterized by a distinct brain connectivity profile.

{ PNAS | Continue reading | Read more }

related { Neurobiological differences between classical and jazz musicians at high and low levels of action planning }

Nature does not work with an end in view

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Neurobiological research on memory has tended to focus on the cellular mechanisms involved in storing information, known as persistence, but much less attention has been paid to those involved in forgetting, also known as transience. It’s often been assumed that an inability to remember comes down to a failure of the mechanisms involved in storing or recalling information. 

“We find plenty of evidence from recent research that there are mechanisms that promote memory loss, and that these are distinct from those involved in storing information,” says co-author Paul Frankland.

One recent study in particular done by Frankland’s lab showed that the growth of new neurons in the hippocampus seems to promote forgetting. This was an interesting finding since this area of the brain generates more cells in young people. The research explored how forgetting in childhood may play a role in why adults typically do not have memories for events that occurred before the age of four years old. 

{ University of Toronto | Continue reading }

art { Masao Mochizuki, The Air Power of the World, 1976 }

‘The second half of a man’s life is made up of nothing but the habits he has acquired during the first half.’ –Dostoyevsky

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When you’re doing two things at once – like listening to the radio while driving – your brain organizes itself into two, functionally independent networks, almost as if you temporarily have two brains. That’s according to a fascinating new study from University of Wisconsin-Madison neuroscientists Shuntaro Sasai and colleagues.

{ Neuroskeptic | Continue reading }

art { Harri Peccinotti }

yesterday never comes back

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Remembering the past is a complex phenomenon that is subject to error. The malleable nature of human memory has led some researchers to argue that our memory systems are not oriented towards flawlessly preserving our past experiences. Indeed, many researchers now agree that remembering is, to some degree, reconstructive. Current theories propose that our capacity to flexibly recombine remembered information from multiple sources – such as distributed memory records, inferences, and expectations – helps us to solve current problems and anticipate future events. One implication of having a reconstructive and flexible memory system is that people can develop rich and coherent autobiographical memories of entire events that never happened.

In this article, we revisit questions about the conditions under which participants in studies of false autobiographical memory come to believe in and remember fictitious childhood experiences. […]

Approximately one-third of participants showed evidence of a false memory, and more than half showed evidence of believing that the [fictitious] event occurred in the past.

{ Memory | Continue reading }

Photo photo { Brooke Nipar }

When you speak, you learn nothing

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Normal aging is known to be accompanied by loss of brain substance.

Machine learning was used to estimate brain ages in meditators and controls.

At age 50, brains of meditators were estimated to be 7.5 years younger than that of controls.

These findings suggest that meditation may be beneficial for brain preservation.

{ NeuroImage | Continue reading }

image { Jonathan Puckey }