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Michel Roland-Guill

Sapiens : "Claire Sergent : « Quand la conscience empêche de voir »" - La Rec... - 0 views

  • Deux théories s'affrontent en effet sur la différence entre perception consciente et non consciente. L'une, alimentée surtout par les études en IRM, prédit qu'il y a une sorte de continuité entre les deux types de traitement : le non-conscient correspondrait à l'activation des mêmes aires cérébrales que le conscient mais avec une intensité moindre. L'autre prédit qu'il existe au contraire une rupture. Nous avons déjà obtenu dans notre laboratoire des résultats allant dans le sens de cette deuxième théorie.
  • Nous avons trouvé que la perception consciente du deuxième mot dépend de la vitesse à laquelle est traité le premier. Nous avons identifié une différence dans la dynamique d'une onde appelée P300 correspondant à l'activité d'un réseau fronto-pariétal. Lorsque le sujet voit le deuxième mot, c'est que cette onde a été rapide pour le premier mot, avec un pic élevé très tôt. Mais, s'il ne voit pas le deuxième mot, l'onde P300 a été moins intense et plus longue pour le premier mot, et elle est carrément absente pour le deuxième mot. C'est donc que le traitement plus long de l'onde P300 pour le premier mot empêche le second d'être perçu.
Michel Roland-Guill

How Our Brains Make Memories / Greg Miller | Science & Nature | Smithsonian Magazine - 0 views

  • Nader, now a neuroscientist at McGill University in Montreal, says his memory of the World Trade Center attack has played a few tricks on him. He recalled seeing television footage on September 11 of the first plane hitting the north tower of the World Trade Center. But he was surprised to learn that such footage aired for the first time the following day. Apparently he wasn’t alone: a 2003 study of 569 college students found that 73 percent shared this misperception.
  • In short, Nader believes that the very act of remembering can change our memories.
  • Nader was born in Cairo, Egypt. His Coptic Christian family faced persecution at the hands of Arab nationalists and fled to Canada in 1970, when he was 4 years old
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  • Memories surrounding a major event like September 11 might be especially susceptible, he says, because we tend to replay them over and over in our minds and in conversation with others—with each repetition having the potential to alter them.
  • He attended college and graduate school at the University of Toronto, and in 1996 joined the New York University lab of Joseph LeDoux, a distinguished neuroscientist who studies how emotions influence memory.
  • Scientists have long known that recording a memory requires adjusting the connections between neurons. Each memory tweaks some tiny subset of the neurons in the brain (the human brain has 100 billion neurons in all), changing the way they communicate. Neurons send messages to one another across narrow gaps called synapses. A synapse is like a bustling port, complete with machinery for sending and receiving cargo—neurotransmitters, specialized chemicals that convey signals between neurons. All of the shipping machinery is built from proteins, the basic building blocks of cells.
  • In five decades of research, Kandel has shown how short-term memories—those lasting a few minutes—involve relatively quick and simple chemical changes to the synapse that make it work more efficiently. Kandel, who won a share of the 2000 Nobel Prize in Physiology or Medicine, found that to build a memory that lasts hours, days or years, neurons must manufacture new proteins and expand the docks, as it were, to make the neurotransmitter traffic run more efficiently. Long-term memories must literally be built into the brain’s synapses. Kandel and other neuroscientists have generally assumed that once a memory is constructed, it is stable and can’t easily be undone. Or, as they put it, the memory is “consolidated.”
  • under ordinary circumstances the content of the memory stays the same, no matter how many times it’s taken out and read. Nader would challenge this idea.
  • Work with rodents dating back to the 1960s didn’t jibe with the consolidation theory. Researchers had found that a memory could be weakened if they gave an animal an electric shock or a drug that interferes with a particular neurotransmitter just after they prompted the animal to recall the memory. This suggested that memories were vulnerable to disruption even after they had been consolidated.
  • the work suggested that filing an old memory away for long-term storage after it had been recalled was surprisingly similar to creating it the first time
  • In the winter of 1999, he taught four rats that a high-pitched beep preceded a mild electric shock. That was easy—rodents learn such pairings after being exposed to them just once. Afterward, the rat freezes in place when it hears the tone. Nader then waited 24 hours, played the tone to reactivate the memory and injected into the rat’s brain a drug that prevents neurons from making new proteins.

    If memories are consolidated just once, when they are first created, he reasoned, the drug would have no effect on the rat’s memory of the tone or on the way it would respond to the tone in the future. But if memories have to be at least partially rebuilt every time they are recalled—down to the synthesizing of fresh neuronal proteins—rats given the drug might later respond as if they had never learned to fear the tone and would ignore it. If so, the study would contradict the standard conception of memory.

  • When Nader later tested the rats, they didn’t freeze after hearing the tone: it was as if they’d forgotten all about it
  • After Nader’s initial findings, some neuroscientists pooh-poohed his work in journal articles and gave him the cold shoulder at scientific meetings. But the data struck a more harmonious chord with some psychologists. After all, their experiments had long suggested that memory can easily be distorted without people realizing it.
  • To Nader and his colleagues, the experiment supports the idea that a memory is re-formed in the process of calling it up. “From our perspective, this looks a lot like memory reconsolidation,” says Oliver Hardt, a postdoctoral researcher in Nader’s lab.
  • “When you retell it, the memory becomes plastic, and whatever is present around you in the environment can interfere with the original content of the memory,” Hardt says.
  • The question is whether reconsolidation—which he thinks Nader has demonstrated compellingly in rat experiments—is the reason for the distortions.
  • at the Douglas Mental Health University Institute. Alain Brunet, a psychologist, is running a clinical trial involving people with post-traumatic stress disorder (PTSD). The hope is that caregivers might be able to weaken the hold of traumatic memories that haunt patients during the day and invade their dreams at night.
  • In Brunet’s first study, PTSD patients took a drug intended to interfere with the reconsolidation of fearful memories. The drug, propranolol, has long been used to treat high blood pressure, and some performers take it to combat stage fright. The drug inhibits a neurotransmitter called norepinephrine. One possible side effect of the drug is memory loss.
  • Nine patients took a propranolol pill and read or watched TV for an hour as the drug took effect. Ten were given a placebo pill.

    Brunet came into the room and made small talk before telling the patient he had a request: he wanted the patient to read a script, based on earlier interviews with the person, describing his or her traumatic experience. The patients, all volunteers, knew that the reading would be part of the experiment. “Some are fine, some start to cry, some need to take a break,” Brunet says.

    A week later, the PTSD patients listened to the script, this time without taking the drug or a placebo. Compared with the patients who had taken a placebo, those who had taken the propranolol a week earlier were now calmer; they had a smaller uptick in their heart rate and they perspired less.

  • The treatment didn’t erase the patients’ memory of what had happened to them; rather, it seems to have changed the quality of that memory. “Week after week the emotional tone of the memory seems weaker,” Brunet says. “They start to care less about that memory.”

    Nader says the traumatic memories of PTSD patients may be stored in the brain in much the same way that a memory of a shock-predicting tone is stored in a rat’s brain. In both cases, recalling the memory opens it to manipulation.

  • Nader suggests that reconsolidation may be the brain’s mechanism for recasting old memories in the light of everything that has happened since. In other words, it just might be what keeps us from living in the past.
  • Elizabeth Loftus
  • Karim Nader
  • Eric Kandel
  • Brunet
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    may 2010
Michel Roland-Guill

Your Outboard Brain Knows All - 0 views

  • My point is that the cyborg future is here. Almost without noticing it, we've outsourced important peripheral brain functions to the silicon around us.
  • Of course, it's probably not an either/or proposition. I want both: I want my organic brain to contain vast stores of knowledge and my silicon overmind to contain a stupidly huge amount more.
  • by offloading data onto silicon, we free our own gray matter for more germanely "human" tasks like brainstorming and daydreaming
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  • the surreal and delightful experience of Googling a topic only to unearth an old post that I don't even remember writing
  • it's what author Cory Doctorow refers to as an "outboard brain."
  • There's another type of intelligence that comes not from rapid-fire pattern recognition but from slowly ingesting and retaining a lifetime's worth of facts.
  • You read War and Peace.
  • Then you let it all ferment in the back of your mind for decades, until, bang, it suddenly coalesces into a brilliant insight.
  • We've come to think of human intelligence as being like an Intel processor, able to quickly analyze data and spot patterns. Maybe there's just as much value in the ability to marinate in the seemingly trivial.
Michel Roland-Guill

Le Figaro - Santé : Les smartphones modifient le fonctionnement du cerveau - 0 views

  • Les développements récents des neurosciences cognitives permettent maintenant d'envisa­ger de véritables programmes d'éducation de l'attention, renseignant sur ses limites et son bon usage. Dans cet univers de multitâche permanent, ce bon usage ne va plus de soi et il est peut-être temps d'envisager une véritable éducation de l'attention, notamment en milieu scolaire, qui prépare dès l'enfance à la vie connectée.
Michel Roland-Guill

Your Brain on Google: Patterns of Cerebral Activation during... : American Journal of G... - 0 views

  • significant increases in signal intensity in additional regions controlling decision making, complex reasoning, and vision
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    "Your Brain on Google: Patterns of Cerebral Activation during Internet Searching"
Michel Roland-Guill

Brain doctor: Spend five hours on the Internet and call me in the morning | j. the Jewi... - 0 views

  • Dr. Gary Small says bringing younger and older people together helps optimize the neural circuitry for both generations.
  • Small, director of the UCLA Center on Aging, described results of research he and colleagues performed with volunteers between the ages of 55 and 76.
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