lunes, 28 de febrero de 2011

"Les jeux vidéo et les réseaux sociaux modifient le rapport à l'espace, au temps, à la construction de l'identité"


Ice Berg : Les "psy" constatent-ils une augmentation des consultations pour des problèmes relationnels ou de comportement liés à l'utilisation grandissante et précoce des écrans ?

Oui, les psychologues et les psychiatres sont aujourd'hui énormément consultés pour l'usage jugé excessif des jeux vidéo ou des nouveaux réseaux sociaux.

Pol : Comprenez-vous l'angoisse des parents sur ce sujet ou la trouvez-vous disproportionnée ?

Les parents ont raison d'être inquiets, mais pas pour la raison qu'ils croient. La consommation excessive d'écrans à l'adolescence n'est, en règle générale, pas le signe de troubles psychologiques. En revanche, c'est vrai que la fréquentation excessive des écrans peut nuire à d'autres activités, et les parents doivent la réguler.

Tom : Pendant quelle durée quotidienne doit-on autoriser les enfants à être devant des écrans (ordinateur, télévision) ?

L'Académie américaine de pédiatrie a proposé en 1999 un guide pour les parents : pas d'écran avant 2 ans (les spécialistes s'accordent aujourd'hui à parler de 3 ans), une heure par jour entre 3 et 6 ans, 2 heures entre 6-9 ans et 3 heures au-delà. Mais il s'agit de temps réel global, incluant la télévision, l'ordinateur pour jouer, l'ordinateur pour travailler, la console portable...

Yan : La télévision et les jeux vidéo font partie de leur époque et de leur quotidien. Comment ne pas les mettre en marge sans tout leur interdire et rentrer en conflit avec leur désir qui semble d'être en phase avec leur temps ?

Pourquoi dit-on que les parents doivent cadrer le temps de jeu ? Parce qu'à l'adolescence, les jeunes n'ont pas encore acquis la possibilité de réguler eux-mêmes leurs impulsions. Ils ont de la difficulté à suivre les décisions qu'ils jugent pourtant les plus raisonnables pour eux. C'est pourquoi les parents doivent veiller à ce que les jeux vidéo n'occupent qu'une partie du temps de loisirs. Mais en même temps, cadrer est totalement insuffisant. Parce que les jeux vidéo comportent beaucoup d'aspects positifs et que les parents ont tout à gagner à s'y intéresser.

Quand les parents accompagnent en s'intéressant aux jeux de leurs enfants, ils savent cadrer avec beaucoup plus d'intelligence et d'efficacité. Cadrer sans accompagner est aussi inutile que vouloir accompagner sans cadrer. Les deux sont indispensables.

Latemotiv : Un enfant face à tous ces écrans peut-il devenir fou ? Et perdre la relation au réel ?

Jlrenck : Qu'en est-il des repères d'espace et de temps chez des jeunes rivés sur ces fenêtres "magiques" par lesquelles – virtuellement – les distances s'abolissent, et l'immédiat devient la norme ? Des signes perceptibles de "mutations", d'incompétences spatio-temporelles, etc., ont-ils été observés ?

La pratique des jeux vidéo, comme celle des nouveaux réseaux sociaux, modifie le rapport à l'espace, au temps, à la construction de l'identité, et à la place que nous donnons aux activités partagées et aux activités solitaires.

Mais une semblable révolution a déjà accompagné d'autres grandes innovations comme l'invention de l'écriture, et, dans une moindre mesure, de la diffusion du livre grâce à l'imprimerie. Les modes de fonctionnement nouveaux repérés chez les enfants et les adolescents ne sont ni meilleurs ni pires que ceux auxquels nous sommes traditionnellement familiers.

La culture des écrans est en train de remplacer celle du livre. Face à ce bouleversement, le pourcentage d'enfants présentant des troubles mentaux reste stable, et eux seuls courent le risque de développer des pathologies. Il ne faut pas confondre la sphère d'activité dans laquelle une pathologie est repérée avec la cause de celle-ci.

Docteur Olive : L'écran est-il comparable à de la drogue, tant au niveau chimique (dopamine...) que psychologique ?

Elvire : L'utilisation quotidienne de consoles de jeux ou d'Internet ne peut-elle pas générer des mécanismes addictifs chez les enfants ? Je constate que mes enfants ont parfois du mal à "décrocher" si je ne les y invite pas fermement.

Dans les années 1990, Aviel Goodman a développé l'idée qu'il existerait des addictions sans substance. Mais à ce jour, il n'y a pas de consensus des spécialistes sur l'existence d'une addiction à l'Internet, au virtuel ou aux jeux vidéo. Pourquoi ? Parce que plus ces jeux évoluent, et plus ils donnent de l'importance à la socialisation via Internet.

Evidemment, l'être humain adore échanger, ou plus précisément bavarder, et nous connaissons tous cela. Mais on ne peut pas dire pour autant qu'il existe une addiction au bavardage. Et c'est ce que font aujourd'hui la plupart des adolescents quand ils vont sur les jeux vidéo ou les réseaux sociaux : bavarder avec leurs copains. Le seul problème est chez ceux qui vont dans les jeux vidéo pour jouer seuls. C'est pourquoi les parents doivent toujours poser la question à leur enfant : "est-ce que tu joues seul ou avec d'autres ?" Jouer seul est le plus inquiétant, et si l'enfant répond qu'il joue avec d'autres, il faut lui demander s'il joue avec d'autres qu'il connaît ou qu'il ne connaît pas. La réponse la plus rassurante est celle où il retrouve le soir dans ses jeux des camarades de classe qu'il côtoie la journée.

Adrien : Les réseaux sociaux ne sont-ils pas des lames à double tranchant : d'un côté, l'incroyable possibilité pour qui l'utilise d'échanger en temps réel et, de l'autre, un cloisonnement autour d'un écran, une certaine solitude face à l'écran ?

Dans les réseaux sociaux, on n'est jamais seul, par définition. D'autant plus que des études ont montré que les jeunes, à la différence des adultes, retrouvent préférentiellement dans ces réseaux des personnes de leur âge, qu'ils connaissent par ailleurs. Les adultes cherchent plutôt à rencontrer des inconnus, avec le désir d'avoir des aventures...

Lapin : L'écran ne risque-t-il pas de remplacer le parent en terme de transmission de normes et de valeurs ?

Il y a longtemps que les enfants cherchent dans les écrans des repères pour savoir comment devenir "grand". La télévision et le cinéma ont toujours constitué de tels repères. Et à partir de là, tout se joue autour de la relation que les enfants ont avec leurs parents. Si ceux-ci fonctionnent selon des règles claires et fiables, les enfants renoncent vite à appliquer les recettes qu'il leur semble découvrir sur les écrans. Mais si les parents n'ont pas de tels repères, ou, pire encore, se détournent de leurs enfants, ceux-ci vont évidemment tenter d'appliquer les modèles des écrans.

C'est la même chose aujourd'hui avec tout ce qu'ils trouvent sur Internet. S'il y a une différence, elle est seulement dans le fait que sur Internet, ils sont non seulement en contact avec des modèles, mais aussi avec la communauté de leurs camarades, ceux qu'on appelle les pairs. C'est pourquoi aujourd'hui, les enfants sont beaucoup plus dépendants des modèles pratiqués par leurs camarades que par le passé. Mais, comme par le passé, la capacité des parents de proposer des repères fiables et récurrents reste essentielle.

Mimie : Je n'ai pas la télé à la maison, seulement un ordinateur sur lequel mes enfants regardent de courts dessins animés. Je passe pour un extra-terrestre mais je me dis que c'est mieux comme ça. Mais cela peut aussi être à double tranchant...

De plus en plus de parents préoccupés par l'influence des écrans sur leurs enfants préfèrent leur mettre des DVD plutôt qu'allumer la télévision. Les règles fixées par l'Académie américaine de pédiatrie en 1999 doivent s'appliquer de la même manière pour ce qui concerne le temps d'écran.

Mais cette formule présente un avantage considérable : permettre à l'enfant de choisir ce qu'il va regarder, de le regarder plusieurs fois s'il en a envie, ce qui lui permet de comprendre mieux l'histoire et de développer sa mémoire. En revanche, ce choix peut conduire l'enfant à ignorer l'existence de feuilletons ou de dessins animés dont ses camarades vont lui parler. Mais l'expérience montre que les enfants dans cette situation s'en débrouillent très bien et qu'il n'y a pas d'inquiétude à avoir, d'autant plus qu'ils s'arrangent toujours pour regarder la télévision chez leurs copains ou... chez leurs grands-parents.

Si les parents n'allument jamais la télévision, il vaut mieux qu'ils expliquent à leur enfant que c'est leur choix mais qu'ils sont tout à fait disposés quand même à parler de ce que l'enfant pourra voir ailleurs qu'à la maison.

Glagla : Les adultes ne sont-ils pas les premiers à donner le "mauvais exemple" en passant eux-mêmes de nombreuses heures chaque semaine à consulter leurs mails ou à échanger avec leurs amis sur les réseaux sociaux ?

Une récente étude américaine a montré que les enfants qui regardent le plus la télévision sont ceux dont les parents regardent le plus la télévision... Autrement dit, si des parents veulent que leurs enfants la regardent moins, le mieux est qu'ils commencent eux-mêmes par réduire leur propre temps d'écran.

Pour ce qui concerne l'utilisation des jeux vidéo en réseau, il semblerait que le fait d'avoir un parent qui joue est plutôt dissuasif pour l'enfant de jouer : le jeu vidéo est en effet vécu comme une manière de fuir les parents, et si eux-mêmes sont joueurs, l'enfant court toujours le risque de se voir donner des conseils qui l'empêcheront de cultiver l'illusion de fuir l'influence des parents, notamment du père.

Enfin, pour ce qui concerne les nouveaux réseaux sociaux, les jeunes y créent leur propre territoire, quel que soit l'usage que les parents en font de leur côté. Finalement, à mon avis, l'important est plutôt de créer dans la famille des moments où chacun peut parler de ses propres usages des écrans. Et le moment privilégié pour cela me paraît être le repas du soir pris en commun... sans écran, justement pour parler des écrans.

Jos : Quels sont les réels désagréments d'une pratique excessive des écrans chez les jeunes enfants (3-6 ans) ? Pouvez-vous les décrire précisément ?

Entre 3 et 6 ans, des études ont montré qu'il est essentiel que l'enfant ait des activités impliquant l'utilisation de ses dix doigts. C'est pour cela que traditionnellement, l'enfant à cet âge était invité à réaliser des découpages, des pliages, des collages, des coloriages... C'est en effet cette activité des dix doigts qui permet la maturation des régions cérébrales qui permettent l'appréhension des objets en trois dimensions. C'est pourquoi il vaut mieux éviter le plus possible que l'enfant à cet âge-là utilise une console de jeu qui ne mobilise que deux ou quatre doigts. Et il faut en particulier bannir complètement les consoles mobiles (Nintendo DS ou PSP), qui accaparent toute l'attention de l'enfant.

Au-delà, le désagrément principal est la réduction des autres activités et la réduction du temps disponible pour en avoir. Il y a tellement de choses à apprendre à cet âge.

Mais on ne peut pas non plus mettre sur le même plan la pratique d'un jeu vidéo et l'exploration de sites Internet. Pour un temps d'écran égal, prendre en compte le type d'activité est essentiel. Tout ce qui socialise l'enfant à travers l'écran et tout ce qui l'invite à se poser des questions et à résoudre des problèmes imprévus, favorise son développement. A l'inverse, toutes les activités de jeu répétitives, stéréotypées, et plus encore solitaires, sont inquiétantes.

Destouche : Que pensez-vous des projets de l'éducation nationale qui veut que les NTICE (nouvelles technologies de l’information, de la communication, et de l’enseignement) envahissent le champ éducatif et que les écoles deviennent des cyber-cafés ?

Le corps enseignant n'est pas prêt à laisser transformer les écoles en cybercafés ! En revanche, l'école a un rôle capital à jouer (comme les parents, mais différemment d'eux) pour que les enfants soient introduits de la meilleure façon aux nouvelles technologies. L'école doit expliquer aux enfants dès l'école primaire les trois règles de base d'Internet : tout ce qu'on y met peut tomber dans le domaine public ; tout ce qu'on y met y restera éternellement ; et tout ce qu'on y trouve est sujet à caution, parce qu'il est impossible de repérer les images de la réalité des images falsifiées.

L'école a également un rôle essentiel à jouer pour expliquer aux enfants les modèles économiques qui sous-tendent Facebook, YouTube, Dailymotion..., et aussi l'importance du droit à la dignité et du droit à l'image. Avant d'être un lieu où l'on utilise les nouvelles technologies, l 'école doit être un lieu où les enseignants les connaissent suffisamment pour mettre les enfants en garde contre leurs dangers et leurs pièges.

Quant à l'utilisation des nouvelles technologies à l'école, les modèles sont encore à l'étude. On s'oriente aujourd'hui dans deux directions : d'abord, la mise au point de jeux vidéo à travers lesquels les enfants puissent acquérir des apprentissages utiles (jeux qu'on appelle "serious games") ; et ensuite, l'utilisation des outils numériques que les enfants possèdent, à commencer par leur téléphone mobile et leur iPod. La meilleure manière qu'ils n'utilisent pas ces machines pour s'échapper des cours est encore de les obliger à travailler avec ! Mais nous ne sommes qu'au début de ces recherches.

Anna : Je constate (mes collègues aussi) chez mes élèves de 9 ans de grosses difficultés de concentration et une nette tendance au zapping. Est-ce lié aux jeux vidéo et à la télévision ?

Le cerveau des nouvelles générations, et d'ailleurs de tous ceux qui sont gros consommateurs de nouvelles technologies, ne fonctionne plus comme par le passé. Le désir d'obtenir une réponse rapide, le fait de passer rapidement d'un sujet à un autre, la difficulté de concentration, tout cela fait partie des nouvelles façons de fonctionner. C'est vrai qu'elles sont inadaptées au système d'enseignement traditionnel. Mais le problème est que rien ne prouve à ce jour qu'elles soient inadaptées au fonctionnement qui sera exigé de chacun d'entre nous dans dix ou vingt ans. On voit déjà de jeunes employés qui sont incapables de se concentrer sur une seule tâche et passent sans cesse de l'une à l'autre pour les résoudre en parallèle, et non plus successivement. C'est très déroutant pour les vieux cadres qui les regardent. Mais ils arrivent à faire le travail pas plus mal que leurs aînés, même si la méthode paraît dérouter la logique qui veut qu'on résolve plusieurs tâches de natures différentes les unes après les autres. Voilà le genre de paradoxe auquel il faut nous habituer.

Certains pédagogues américains suggèrent même que la seule chose qu'il faudrait apprendre aux élèves serait la programmation de machines, car demain l'humanité se divisera en deux : ceux qui savent les utiliser (pensons à nos smartphones d'aujourd'hui !) et ceux qui sauront si mal le faire qu'ils seront rapidement marginalisés. C'est pourquoi les enseignants doivent s'engager eux-mêmes dans l'usage des nouvelles technologies pour mesurer l'ampleur des bouleversements qu'elles imposent au fonctionnement psychique et aux procédures d'apprentissage, et relativiser leurs dangers possibles.

Didon : Comment choisir les dessins animés que peuvent regarder des petits enfants à partir de 2 ans et demi ?

Rappelez-vous que le Conseil supérieur de l'audiovisuel a repris à son compte le slogan "Pas d'écran avant 3 ans". Cela ne signifie pas qu'un enfant soit menacé dans son développement s'il regarde une demi-heure ou une heure de télévision par jour. Mais cela signifie qu'il a toujours mieux à faire, parce qu'à cet âge-là, ce qui importe, c'est qu'il puisse interagir avec le monde environnant d'une manière qui fasse intervenir tous ses sens.

La télévision nous offre une relation réduite à la vue et à l'audition. Si un enfant n'a jamais l'occasion de regarder les programmes que les parents regardent pour eux, pourquoi en effet ne pas lui mettre de temps en temps un dessin animé ? Mais avant l'âge de 3 ans, et même un peu au-delà, il n'y comprendra rien de toute façon. Seuls comptent le rythme, qui doit plutôt être lent, et les couleurs, plutôt harmonieuses...

Tom : Pensez-vous qu'il y a un âge limite pour avoir un téléphone portable ?

L'âge auquel les parents achètent un téléphone portable à leur enfant baisse de plus en plus. Il n'est pas rare aujourd'hui de voir des enfants en posséder en CM1. La seule chose que je peux dire aux parents, c'est que plus tôt un enfant aura un téléphone portable, et plus rapidement il s'éloignera de ses parents. A partir de là, tout dépend donc de leurchoix...

viernes, 25 de febrero de 2011

Cursos de Neuroartes en Tijuana. Marzo 2011.

Meditation beats dance for harmonizing body and mind



Meditation beats dance for harmonizing body and mind
February 24th, 2011 in Medicine & Health / Psychology & Psychiatry
Enlarge

The body is a dancer's instrument, but is it attuned to the mind? A new study from the University of California, Berkeley, suggests that professional ballet and modern dancers are not as emotionally in sync with their bodies as are people who regularly practice meditation.

UC Berkeley researchers tracked how closely the emotions of seasoned meditators and professional dancers followed bodily changes such as breathing and heart rates.

They found that dancers who devote enormous time and effort to developing awareness of and precise control over their muscles – a theme coincidentally raised in the new ballet movie “Black Swan” – do not have a stronger mind-body connection than do most other people.

By contrast, veteran practitioners of Vipassana or mindfulness meditation – a technique focused on observing breathing, heartbeat, thoughts and feelings without judgment – showed the closest mind-body bond, according to the study recently published in the journal Emotion.

“We all talk about our emotions as if they are intimately connected to our bodies – such as the ‘heartache of sadness’ and ‘bursting a blood vessel’ in anger,” said Robert Levenson, a UC Berkeley psychology professor and senior author of the study. “We sought to precisely measure how close that connection was, and found it was stronger for meditators.”

The results offer new clues in the mystery of the mind-body connection. Previous studies have linked the dissociation of mind and body to various medical and psychiatric diseases.

“Ever have the experience of getting home from work and realizing you have a blistering headache?” said Jocelyn Sze, a doctoral student in clinical science at UC Berkeley and the lead author of the study. “The headache probably built up throughout the day, but you might have been intentionally ignoring it and convincing yourself that you felt fine so that you could get through the demands of the day.”

Increasingly, mindfulness meditation is being used to treat physical and psychological problems, researchers point out. “We believe that some of these health benefits derive from meditation’s capacity to increase the association between mind and body in emotion,” Levenson said.

For the experiment, the researchers recruited volunteers from meditation and dance centers around the San Francisco Bay Area and via Craigslist. The study sample consisted of 21 dancers with at least two years of training in modern dance or ballet and 21 seasoned meditators with at least two years of Vipassana practice. A third “control group” was made up of 21 moderately active adults with no training in dance, meditation, Pilates or professional sports.

Participants, who ranged in age from 18 to 40, were wired with electrodes to measure their bodily responses while they watched emotionally charged scenes from movies and used a rating dial to indicate how they were feeling.

Although all participants reported similar emotional reactions to the film clips, meditators showed stronger correlations between the emotions they reported feeling and the speed of their heartbeats. Surprisingly, the differences between dancers and the control group were minimal.

Researchers theorize that dancers learn to shift focus between time, music, space, and muscles and achieve heightened awareness of their muscle tone, body alignment and posture.

“These are all very helpful for becoming a better dancer, but they do not tighten the links between mind and body in emotion,” Levenson said.

By contrast, meditators practice attending to “visceral” body sensations, which makes them more attuned to internal organs such as the heart. “These types of visceral sensations are a primary focus of Vipassana meditation, which is typically done sitting still and paying attention to internal sensations,” Sze said.

More information: The study was published in the December 2010 issue of Emotion.


Provided by University of California - Berkeley

jueves, 24 de febrero de 2011

Brain's 'reward' center also responds to bad experiences


Brain's 'reward' center also responds to bad experiences
February 22nd, 2011 in Medicine & Health / Neuroscience


Dr. Joe Z. Tsien of Georgia Health Sciences University has shown that the "reward" center of the brain also responds to bad experiences. Credit: Phil Jones/GHSU Photographer

The so-called reward center of the brain may need a new name, say scientists who have shown it responds to good and bad experiences. The finding, published in PLoS One, may help explain the "thrill" of thrill-seeking behavior or maybe just the thrill of surviving it, according to scientists at Georgia Health Sciences University and East China Normal University.

Eating chocolate or falling off a building – or just the thought of either – can evoke production of dopamine, a neurotransmitter that can make the heart race and motivate behavior, said Dr. Joe Z. Tsien, Co-Director of GHSU's Brain & Behavior Discovery Institute.

Scientists looked at dopamine neurons in the ventral tegmental area of the mouse brain, widely studied for its role in reward-related motivation or drug addiction. They found essentially all the cells had some response to good or bad experiences while a fearful event excited about 25 percent of the neurons, spurring more dopamine production.

Interestingly neuronal response lasted as long as the event and context was important, Tsien said. Scientists used a conditioned tone to correlate a certain setting with a good or bad event and later, all it took was the tone in that setting to evoke the same response from the dopamine neurons of mice.

"We have believed that dopamine was always engaged in reward and processing the hedonic feeling," Tsien said. "What we have found is that dopamine neurons also are stimulated or respond to negative events."

Just how eating chocolate or jumping off a building induces dopamine production remains a mystery. "That is just the way the brain is wired," Tsien said. He notes that genetics can impact the number of cells activated by bad events – and while interpretation of the findings needs more work – they could help explain inappropriate behaviors such as drug addiction or other risky habits.

In a second paper in PLoS One, Tsien and his colleagues at Boston University have provided more insight into how brains decide how much to remember good or bad. Inside the hippocampus, where memory and knowledge are believe to be formed, recordings from hundreds of mouse brain cells in a region called CA1 showed all are involved in sensing what happens, but not in the same way.

They found among most cells a big event, such as a major earthquake, evoked a bigger sensory response than a mild earthquake. But slightly less than half the cells involved logged a more consistent neural response to all events big and small. These are called invariant cells because of their consistent firing regardless of event intensity. Tsien said these cells are critical in helping the brain remember those events.

The initial muted sensory response was followed by the cells replaying what they just experienced. It's that reverberation that corresponds with learning and memory. "If they play it over and over, you can remember it for a long time," Tsien said of these memory makers.

But these invariant cells vary in that some keep replaying specific memories while the majority focus on more general features of what occurred. "The general-knowledge cells have the 'highest volume,'" Tsien said. "So we walk away with general knowledge that will guide your life, which is more important than the details."

As with the number of dopamine cells that respond to bad or risky behavior, genetics likely plays a role in an individual's specific ratio of cells involved in encoding general versus more detailed memories, Tsien said. A person with a photographic memory likely has more of the specific memory makers while those with autism or schizophrenia, who have difficulty coping in society, may have fewer of the general memory makers that help provide correct context and understanding of complex relationships.

Provided by Georgia Health Sciences University

martes, 22 de febrero de 2011

Look after your brain


Look after your brain
February 20th, 2011 in Medicine & Health / Diseases


As the average life span becomes longer, dementia becomes more common. Swedish scientist Laura Fratiglioni has shown that everyone can minimize his or her risk of being affected. Factors from blood pressure and weight to the degree of physical and mental activity can influence cognitive functioning as one gets older.

The lengthening of the average life span in the population has caused an increase in the prevalence of aging related disorders, one of which is cognitive impairment and dementia. An expert panel estimates that worldwide more than 24 million people are affected by dementia, most suffering from Alzheimer's disease. In the more developed countries, 70 percent of the persons with dementia are 75 years or older.

Age is the greatest risk factor for developing dementia. But there is growing evidence that the strong association with increasing age can be, at least partially, explained by a life course cumulative exposure to different risk factors.

Laura Fratiglioni's research group at Karolinska Institutet is a leader in identifying the risk factors that lie behind developing dementia and using this knowledge to develop possible preventative strategies. The group's research has shown that the risk is partly determined by an individual genetic susceptibility, and that active involvement in mental, physical and social activities can delay the onset of dementia by preserving cognitive functions. Further education early in life has a protective effect, and the group's research has shown that it is never too late to get started.

"The brain, just as other parts of the body, requires stimulation and exercise in order to continue to function. Elderly people with an active life – mentally, physically and socially – run a lower risk of developing dementia, and it doesn't matter what the particular activities are", says Professor Laura Fratiglioni.

Laura Fratiglioni's research has shown that physical factors are also significant. Not only high and low blood pressure, but also diabetes and obesity when middle-aged increase the risk of developing dementia after the age of 70. "What is good for the heart is good for the brain", she says.

Knowledge about risk factors and how to protect the brain from dementia is based on observational studies in which scientists have discovered statistical correlations in the population. Scientists in other current studies that are carried out in Europe are investigating what happens when a large number of study participants are given special help to better control vascular risk factors and to stimulate social, physical and mental activities. which should, at least, lead to a delay of dementia onset.

"You could say that we are progressing from observation to experiment. This means that in a few years we will know more about which strategies are most effective in preventing neurodegenerative disorders", says Laura Fratiglioni.

Provided by Karolinska Institutet

sábado, 19 de febrero de 2011

Model-driven therapeutic treatment of neurological disorders: reshaping brain rhythms with neuromodulation


Model-driven therapeutic treatment of neurological disorders: reshaping brain rhythms with neuromodulation
Julien Modolo 1,2, Alexandre Legros 1,2, Alex W. Thomas 1,2 and Anne Beuter 1,3

1Lawson Health Research Institute, St Joseph Health Care, 268 Grosvenor Street, London, Canada
2Department of Medical Biophysics, University of Western Ontario, London, Canada
3Bordeaux Polytechnic Institute, University of Bordeaux, 16 avenue Pey-Berland, Pessac, France
*Author for correspondence (anne.beuter@ensc.fr).
Abstract
Electric stimulation has been investigated for several decades to treat, with various degrees of success, a broad spectrum of neurological disorders. Historically, the development of these methods has been largely empirical but has led to a remarkably efficient, yet invasive treatment: deep brain stimulation (DBS). However, the efficiency of DBS is limited by our lack of understanding of the underlying physiological mechanisms and by the complex relationship existing between brain processing and behaviour. Biophysical modelling of brain activity, describing multi-scale spatio-temporal patterns of neuronal activity using a mathematical model and taking into account the physical properties of brain tissue, represents one way to fill this gap. In this review, we illustrate how biophysical modelling is beginning to emerge as a driving force orienting the development of innovative brain stimulation methods that may move DBS forward. We present examples of modelling works that have provided fruitful insights in regards to DBS underlying mechanisms, and others that also suggest potential improvements for this neurosurgical procedure. The reviewed literature emphasizes that biophysical modelling is a valuable tool to assist a rational development of electrical and/or magnetic brain stimulation methods tailored to both the disease and the patient's characteristics.

Source: The Royal Society
http://rsfs.royalsocietypublishing.org/content/1/1/61.abstract?etoc

miércoles, 16 de febrero de 2011

Biologists gain new insights into brain circuit wiring


Biologists gain new insights into brain circuit wiring
February 14th, 2011 in Medicine & Health / Neuroscience


Neurobiologists at UC San Diego have discovered new ways by which nerves are guided to grow in highly directed ways to wire the brain during embryonic development.

Their finding, detailed in a paper in the February 15 issue of the journal Developmental Cell, provides a critical piece of understanding to the longstanding puzzle of how the human brain wires itself into the complex networks that underlie our behavior.

The discovery concerns the movements of a highly sensitive and motile structure at the tips of growing nerves called a growth cone. For more than a century, biologists have known that growth cones find their targets by detecting chemical cues in the developing nervous system. They do that by responding to gradients of chemical concentration and steering nerve cells either up or down the gradient to eventually find the right targets to make the proper nerve connections that then establish neuronal networks.

While many of these chemical guidance cues have been identified over the past decade, scientists still don't fully understand how the growth cone picks up small concentration differences in the developing embryo or how guidance cues enter the growth cone to regulate the cellular machinery to turn growth cones in one direction or another.

Yimin Zou, an associate professor of neurobiology at UC San Diego, and his colleagues had previously shown that a family of proteins known as "Wnt morphogens" provide the directional cues for the wiring of circuits in many parts of the developing brain.

"These morphogens are often strategically placed in important organizing centers of the developing nervous system and play a major role in sculpting brain connections," said Zou.

In their latest paper, Zou and his UCSD colleagues, Beth Shafer, Keisuke Onishi, Charles Lo and Gulsen Colakoglu, report their discovery that Wnt proteins steer the growth cone by stimulating planar cell polarity signaling.

"Planar cell polarity or PCP refers to the polarized structures and functions of a sheet of epithelial cells along the plane of the tissue," he said. "The direction of our skin hair in our backs, for example, is polarized to point down from our head and a highly conserved genetic program, the PCP signaling system, ensures this type of tissue organization in our skin as well as many other parts of our body."

The UCSD research team found that the growth cone is equipped with all the PCP components necessary to steer extensions of nerve cells, or axons, to their proper targets within the Wnt gradients.

"This study reveals a novel type of environmental signal which the growth cone responds to, previously unknown to developmental neurobiologists, the tissue polarity signals," said Zou. "Tissue polarity is a long lasting structural feature and may provide organizational information to axonal connections while the brain is being wired up. Because PCP signaling is essential for the beautifully organized structures in the brain, the brain may owe a large part of its stunning axonal organization to the function of PCP signaling. PCP signaling relies heavily on cell-cell interactions, which may pave way for developmental neuroscientists to understand how groups of neurons organize their axons into exquisite patterns."

The UCSD researchers also found that one of the PCP components, Vangl2, is highly enriched on the tips of growing filopodia on the growth cone.

"The filopodia are the motile structures that explore the environment," said Zou. "It has been long speculated that the long filopodia can extend the span of the growth cone to sample larger concentration drops. The localization of Vangl2 on growth cone tips suggests that the tips are more sensitive to guidance cues than the rest of the growth cone."

"This paper not only reveals the profound logic of brain wiring mechanisms but also provides satisfactory and in-depth mechanistic insights," he added. "With these new insights and tools at hand, one can now move on to design experiments to ask the next level questions, such as the cell biological mechanisms of growth cone steering. These findings will also provide new methods for nervous system repair and regeneration."

Provided by University of California - San Diego

jueves, 10 de febrero de 2011

Communication breakdown: Early defects in sensory synapses in motor neuron disease


Communication breakdown: Early defects in sensory synapses in motor neuron disease,
February 9th, 2011 in Medicine & Health / Neuroscience


New research using a mouse model of the motor neuron disease spinal muscular atrophy (SMA) reveals an abnormality in the way that sensory information is relayed to motor neurons in the spinal cord. Importantly, this disruption in communication occurs very early in disease progression and precedes the neuronal death and muscle weakness that are the hallmark of the disease. The study, published by Cell Press in the February 10 issue of the journal Neuron, suggests that therapeutic strategies designed to improve communication at these spinal synapses might help to slow or prevent the progression of the disease and should be further explored.

Amyotrophic lateral sclerosis (ALS) and SMA are human motor neuron diseases characterized by degeneration and death of motor neurons and the muscles that they innervate. Most research on motor neuron diseases has focused on the communication, or synapse, between the neuron and the muscle. However, because these motor neurons originate in the spinal cord and rely on inputs from sensory neurons as well as other neurons from different regions of the brain and spinal cord, it is possible that upstream events might contribute to disease pathology. "There is some evidence that spinal circuit abnormalities might occur in human motor neuron disease," explains the principal author of the study, Dr. George Z. Mentis, who moved last year to the Motor Neuron Center at Columbia University from the National Institute of Neurological Disease and Stroke, where the study was initiated. "However, little is known about the response of these synapses to the factors that trigger disease."

Using a mouse model of SMA that exhibits many of the features of human SMA, including a stereotypical pattern of progressive muscle weakness, Dr. Mentis and colleagues studied synaptic connections between sensory and motor neurons in the spinal cord. "We found that communication between the sensory and motor neurons that make up the stretch reflex, which is known to be important for motor function, showed massive and progressive failure early in the disease process," says Dr. Mentis. The functional deficit mirrored the pattern of muscle weakness in human SMA patients. The researchers went on to show that a drug that has been shown to improve motor function and increase survival of SMA mice improved the sensory-motor circuitry.

"Collectively, our findings suggest that spinal circuit dysfunction is one of the earliest and most pronounced pathological features of the disease and therefore may contribute significantly to the loss of motor function that characterize both mouse models and human SMA patients," concludes Dr. Mentis. "Our data also support the potential therapeutic use of drugs to improve synaptic function, which is likely to be a key factor in the restoration of normal motor function in this disease."

Provided by Cell Press

miércoles, 9 de febrero de 2011

Researchers working on tiny, implantable computers to restore lost brain functions


Researchers working on tiny, implantable computers to restore lost brain functions
February 8th, 2011 in Medicine & Health / Research


Dr. Eberhard Fetz at the University of Washington in Seattle is principal investigator on a W.M. Keck Foundation grant to develop tiny, implantable computers to restore brain functions lost to injury or disease. Credit: Leila Gray

Tiny, implantable computers that would restore brain function lost to disease or injury is the goal of University of Washington research recently funded by a $1 million, three-year grant from the W.M. Keck Foundation.

The UW has made significant progress in neural engineering – the study of communication and control between biological and machine systems. The Keck project is the next step in advancing the technology of miniature devices developed at the UW to record from and stimulate the brain, spinal cord and muscles.

The principal investigator on the Keck Foundation grant is Dr. Eberhard E. Fetz, UW professor of physiology and biophysics and a core staff researcher at the Washington National Primate Research Center. He and his colleagues have successfully deployed tiny, battery-powered implantable brain-computer interfaces called neurochips in animals.

The neurochip can record nerve cell activity in one part of the brain, process this activity and then stimulate cells in another brain region. The battery-powered device operates continuously during free behavior. When primates carry out their usual daily activities – socializing, climbing, eating, and exploring – their brains can learn to exploit these new resources under normal behavioral conditions.

One potential clinical application is to bridge lost biological connections. For example, the researchers have shown that monkeys can learn to bypass an anesthetic block in the nerves of the arm and to activate temporarily paralyzed muscles with activity of cortical neurons. In some ways the device acts as a volition processor, tapping into signals representing the will to move and using them to stimulate the paralyzed muscles to reach targets.

"Using an implantable computer interface to implement novel interactions between brain sites opens many fundamentally new research directions," Fetz said, "depending on the site of recording and stimulation, and how these signals are processed and transformed."

He explained that a second application is to promote neural plasticity, which could strengthen connections and allow some of the brain's functions to be rescued when impaired. This happens naturally when people recover the ability to move or speak again after a stroke or brain injury. The bidirectional brain computer interface could facilitate this recovery and exploit the brain's innate talent for re-organizing itself as it heals.

"We expect that the recurrent type of brain computer interface we are trying to develop," he added, "will eventually have numerous clinical applications for bridging damaged biological pathways and strengthening weak neural connections." For example, signals from the motor-control regions of the brain can be used to stimulate parts of the spinal cord to evoke coordinated movements. This would create connections that could replace lost pathways between the brain and spinal cord, a loss that occurs with strokes and spinal cord injuries.

Many labs around the world are working on brain-computer interfaces that convert neural activity to control of external devices such as prosthetic limbs or computer cursors. What makes the recently funded project unusual is that its scientists are developing a recurrent implantable device that would interact bidirectionally with the brain. By operating autonomously and continuously, without the need for connection to external instrumentation, it would facilitate long-term behavioral adaptation and plasticity.

The proposed research plans to develop this new paradigm to promote restoration of brain, spine, and muscle function. The work could eventually lead to miniaturized electrical and biological interfaces that operate around the clock on a small amount of power while the wearer goes about his or her usual activities, according to Fetz. He added that, if successful, this implantable technology would advance the ability of subjects to effectively control a brain computer interface by allowing long-term adaptation to consistent contingencies, and would open opportunities for the brain to exploit bidirectional interactions with miniature computers. This implementation of continuous reciprocal interaction goes beyond the existing paradigm of using brain signals to control external devices through tethered connections.

As part of the project the team also plans to create a powerful multichannel "Keck Active Electrode Array" with integrated electronics to record and stimulate large numbers of brain sites. This array would operate with electrodes on the surface of the brain and be less invasive than penetrating intracortical electrodes.

To overcome the many technical problems in creating safe, effective devices of this nature and realizing their clinical potential, the project depends on a team of UW experts in different fields.

Dr. Brian Otis, UW assistant professor of electrical engineering, has extensive experience in wireless sensors and in designing extremely small radios that can be incorporated into other devices. He is also an expert in bioelectronics and the processing of signals with minimal power. His group will design and miniaturize the low power circuitry for the computer and the signal amplifiers, and will work toward harvesting energy to operate the device, perhaps from the body's own heat or muscle activity.

Dr. Babak Parviz, the UW McMorrow Innovation Associate Professor of Electrical Engineering, has skill in the fabrication of micro- and nano-scale tools, self-assembled biocompatible machinery, and sensors for detecting very faint signals. His group will create the specialized electrode arrays for recording and stimulation, and will help integrate the miniature electronic systems used in the project.

Dr. Jeffrey Ojemann, UW professor of neurological surgery, has expanded his father's original studies on mapping of the human brain to identify critical areas for movement, language, memory and other functions prior to epilepsy surgery. He will bring his extensive knowledge of functional brain mapping and clinical recording of signals from the human brain to the project. He will help design and test the custom computer-enabled electrode arrays for potential applications to patient care.

Among the engineering and health issues the team will be addressing are integrating the electronics with the electrode array and making it small enough, finding a reliable source of the low power necessary to operate the system, evaluating any hazards the device might pose or serious long-term side effects, and developing biomaterials that won't cause irritation or be rejected, as well as meeting other safety, performance, and acceptability criteria.

"We are extremely grateful to the Keck Foundation for supporting this highly ambitious endeavor," Fetz said. "Looking ahead, we can anticipate that future innovations in nanotechnology, computers and brain science will advance this effort beyond the current state of the art. The grant allows us to be poised to incorporate these advances into the development of more powerful recurrent brain computer interfaces. We expect that these devices will have numerous applications in basic neuroscience research and as well as in clinical care."

Provided by University of Washington

viernes, 4 de febrero de 2011

Why do we sleep?


Why do we sleep?
February 3rd, 2011 in Medicine & Health / Research

Credit: Chau Dang, LTD Space

While we can more or less abstain from some basic biological urges—for food, drink, and sex—we can’t do the same for sleep. At some point, no matter how much espresso we drink, we just crash. And every animal that’s been studied, from the fruit fly to the frog, also exhibits some sort of sleep-like behavior. (Paul Sternberg, Morgan Professor of Biology, was one of the first to show that even a millimeter-long worm called a nematode falls into some sort of somnolent state.) But why do we—and the rest of the animal kingdom—sleep in the first place?

“We spend so much of our time sleeping that it must be doing something important,” says David Prober, assistant professor of biology and an expert on how genes and neurons regulate sleep. Yes, we snooze in order to rest and recuperate, but what that means at the molecular, genetic, or even cellular level remains a mystery. “Saying that we sleep because we’re tired is like saying we eat because we’re hungry,” Prober says. “That doesn’t explain why it’s better to eat some foods rather than others and what those different kinds of foods do for us.”

No one knows exactly why we slumber, Prober says, but there are four main hypotheses. The first is that sleeping allows the body to repair cells damaged by metabolic byproducts called free radicals. The production of these highly reactive substances increases during the day, when metabolism is faster. Indeed, scientists have found that the expression of genes involved in fixing cells gets kicked up a notch during sleep. This hypothesis is consistent with the fact that smaller animals, which tend to have higher metabolic rates (and therefore produce more free radicals), tend to sleep more. For example, some mice sleep for 20 hours a day, while giraffes and elephants only need two- to three-hour power naps.

Another idea is that sleep helps replenish fuel, which is burned while awake. One possible fuel is ATP, the all-purpose energy-carrying molecule, which creates an end product called adenosine when burned. So when ATP is low, adenosine is high, which tells the body that it’s time to sleep. While a postdoc at Harvard, Prober helped lead some experiments in which zebrafish were given drugs that prevented adenosine from latching onto receptor molecules, causing the fish to sleep less. But when given drugs with the opposite effect, they slept more. He has since expanded on these studies at Caltech.

Sleep might also be a time for your brain to do a little housekeeping. As you learn and absorb information throughout the day, you’re constantly generating new synapses, the junctions between neurons through which brain signals travel. But your skull has limited space, so bedtime might be when superfluous synapses are cleaned out.

And finally, during your daily slumber, your brain might be replaying the events of the day, reinforcing memory and learning. Thanos Siapas, associate professor of computation and neural systems, is one of several scientists who have done experiments that suggest this explanation for sleep. He and his colleagues looked at the brain activity of rats while the rodents ran through a maze and then again while they slept. The patterns were similar, suggesting the rats were reliving their day while asleep.

Of course, the real reason for sleep could be any combination of these four ideas, Prober says. Or perhaps only one of these hypotheses might have been true in the evolutionary past, but as organisms evolved, they developed additional uses for sleep.

Researchers in Prober’s lab look for the genetic and neural systems that affect zebrafish sleeping patterns by tweaking their genes and watching them doze off. An overhead camera records hundreds of tiny zebrafish larvae as they swim in an array of shallow square dishes. A computer automatically determines whether the fish are awake or not based on whether they’re moving or still, and whether they respond to various stimuli. Prober has identified about 500 drugs that affect their sleeping patterns, and now his lab is searching for the relevant genetic pathways. By studying the fish, the researchers hope to better understand sleep in more complex organisms like humans. “Even if we find only a few new genes, that’ll really open up the field,” he says. The future is promising, he adds, and for that, it’ll be well worth staying awake.

Provided by California Institute of Technology

miércoles, 2 de febrero de 2011

Sleep selectively stores useful memories


Sleep selectively stores useful memories
February 1st, 2011 in Medicine & Health / Neuroscience


After a good night's sleep, people remember information better when they know it will be useful in the future, according to a new study in the Feb. 2 issue of The Journal of Neuroscience. The findings suggest that the brain evaluates memories during sleep and preferentially retains the ones that are most relevant.

Humans take in large amounts of information every day. Most is encoded into memories by the brain and initially stored, but the majority of information is quickly forgotten. In this study, a team of researchers led by Jan Born, PhD, of the University of Lubeck in Germany set out to determine how the brain decides what to keep and what to forget.

"Our results show that memory consolidation during sleep indeed involves a basic selection process that determines which of the many pieces of the day's information is sent to long-term storage," Born said. "Our findings also indicate that information relevant for future demands is selected foremost for storage."

The researchers set up two experiments to test memory retrieval in a total of 191 volunteers. In the first experiment, people were asked to learn 40 pairs of words. Participants in the second experiment played a card game where they matched pictures of animals and objects — similar to the game Concentration — and also practiced sequences of finger taps.

In both groups, half the volunteers were told immediately following the tasks that they would be tested in 10 hours. In fact, all participants were later tested on how well they recalled their tasks.

Some, but not all, of the volunteers were allowed to sleep between the time they learned the tasks and the tests. As the authors expected, the people who slept performed better than those who didn't. But more importantly, only the people who slept and knew a test was coming had substantially improved memory recall.

The researchers also recorded electroencephalograms (EEG) from the individuals who were allowed to sleep. They found an increase in brain activity during deep or "slow wave" sleep when the volunteers knew they would be tested for memory recall.

"The more slow wave activity the sleeping participants had, the better their memory was during the recall test 10 hours later," Born said. Scientists have long thought that sleep is important in memory consolidation. The authors suggest that the brain's prefrontal cortex "tags" memories deemed relevant while awake and the hippocampus consolidates these memories during sleep.

Gilles Einstein, PhD, an expert in memory at Furman University, said the new findings help explain why you are more likely to remember a conversation about impending road construction than chitchat about yesterday's weather. "These results suggest that sleep is critical to this memory enhancement," said Einstein, who was unaffiliated with the study. "This benefit extends to both declarative memories (memory for a road detour) and procedural memories (memory for a new dance step)."

Provided by Society for Neuroscience

martes, 1 de febrero de 2011

Neuroscientists find memory storage, reactivation process more complex than previously thought


Neuroscientists find memory storage, reactivation process more complex than previously thought
January 31st, 2011 in Medicine & Health / Neuroscience


The process we use to store memories is more complex than previously thought, New York University neuroscientists have found. Their research, which appears in the journal the Proceedings of the National Academy of Sciences, underscores the challenges in addressing memory-related ailments, such as post-traumatic stress disorder.

The researchers looked at memory consolidation and reconsolidation. Memory consolidation is the neurological process we undergo to store memories after an experience. However, memory is dynamic and changes when new experiences bring to mind old memories. As a result, the act of remembering makes the memory vulnerable until it is stored again—this process is called reconsolidation. During this period, new information may be incorporated into the old memory.

It has been well-established that the synthesis of new proteins within neurons is necessary for memory storage. More specifically, this process is important for stabilizing memories because it triggers the production of new proteins that are required for molecular and synaptic changes during both consolidation and reconsolidation.

The purpose of the NYU study was to determine if there were differences between memory consolidation and reconsolidation during protein synthesis. Similar comparative studies have been conducted, but those focused on elongation, one of the latter stages of protein synthesis; the PNAS research considered the initiation stage, or the first step of this process.

Using laboratory rats as subjects, the researchers used mild electric shocks paired with an audible tone to generate a specific associative fear memory and, with it, memory consolidation. They played the audible tone one day later—a step designed to initiate recall of the earlier fear memory and bring about reconsolidation. During both of these steps, the rats were injected with a drug designed to inhibit the initiation stage of protein synthesis.

Their results showed that the inhibitor could effectively interfere with memory consolidation, but had no impact on memory reconsolidation.

"Our results show the different effects of specifically inhibiting the initiation of protein synthesis on memory consolidation and reconsolidation, making clear these two processes have greater variation than previously thought," explained Eric Klann, a professor at NYU's Center for Neural Science and one of the study's co-authors. "Because addressing memory-related afflictions, such at PTSD, depends on first understanding the nature of memory formation and the playback of those memories, finding remedies may prove even more challenging than is currently recognized."

Provided by New York University