miércoles, 25 de marzo de 2009
lunes, 2 de marzo de 2009
Espejos Rotos
ESPEJOS
ROTOS
UNA TEORIA DEL AUTISMO
Los estudios en el sistema de neuronas en espejo pueden revelar pistas sobre las causas del autismo y ayudar a los investigadores a desarrollar nuevas maneras de diagnosticar y tratar el desorden.
Por Vilayanur S. Ramachandran y
Lindsay M. Oberman
En un primer vistazo si conocieses a un chico con autismo no podrías reconocer nada raro. No obstante, si tratas de hablar con él, rápidamente te sería obvio que algo está seriamente mal. Él no puede tener contacto visual contigo; de hecho puede evitar tu mirada y agitarse, mecer su cuerpo de un lado a otro, o golpear su cabeza contra un muro. Más desconcertante, él puede no ser capaz de llevar a cabo lo que remotamente parezca una conversación normal. Aunque él puede experimentar emociones tales como el miedo, rabia y placer, puede tener una genuina falta de empatía hacia otras personas y ser inconciente a las señales sociales sutiles que la mayoría de los niños podría captar con facilidad. En 1940 dos médicos – el psiquiatra americano Leo Kanner y el austriaco Hans Aspergen – independientemente descubrieron este desorden del desarrollo, el cual aflige a cerca de 0.5 por ciento de los chicos america-nos. Ninguno de los investigadores tenía conocimiento del trabajo del otro, y aun por una extraña coincidencia cada uno le dio al síndrome el mismo nombre: autismo, el cual deriva de la palabra Griega autos, que significa “solo.” El nombre es adecuado, ya que la mayoría de las características conspicuas del desorden es una falta de de la interacción social.Más recientemente, los médicos han adoptado el término “espectro del desorden del autismo” para hacer claro que la enfermedad posee muchas variantes relacionadas que oscilan ampliamente en cuanto a severidad aunque comparten algunos síntomas característicos.Desde que el autismo fue identificado, los investigadores han luchado por determinar que lo causa.
Los científicos saben que la susceptibilidad al autismo es heredado, aunque los factores de riesgo ambientales también parecen jugar un papel [ver “Los Orígenes del Autismo” por Patricia M. Rodier: Scientific American, Febrero 2000].
A finales de 1990, los investigadores de nuestro laboratorio de Universidad de California, San Diego, se dispusieron a explorar si existía una conexión entre el autismo y una recientemente descubierta clase de célula nerviosa, dentro del cerebro, llamadas neuronas en espejo. Debido a que estas neuronas al parecer están involucradas en habilidades tales como la empatía y la percepción de otras intenciones individuales, parecía lógico plantear la hipótesis que una disfunción en el sistema de las neuronas en espejo podría resultar en algunos de los síntomas del autismo. Sobre la pasada década varios estudios han proporcionado la evidencia para esta teoría. Más investigaciones de las neuronas en espejo pueden explicar como surge el autismo, y en los procesos médicos estás pueden desarrollar mejores formas de diagnostico y tratar exitosamente el desorden.
miércoles, 11 de febrero de 2009
Evolution
Commentary
The Evolution Of Evolution
Hana R. Alberts, 02.05.09, 06:00 PM EST
Surveying a landscape of cognition--and controversy.
Evolution is change over time.
This characterization can, of course, refer to the way species morph during their histories--minor adjustments in the curve of a beak, the span of a flipper, the size of a brain. At its most basic level, this kind of development attempts to explain how and why organisms' physical or mental attributes equip them to best survive in diverse, often harsh, environments.
But especially this year--as the 200th anniversary of Charles Darwin's birth and the 150th of his publication of On the Origin of Species excites widespread reflection and analysis among biophiles worldwide--that pithy definition is particularly apt.
Science at its core is not static; in fact, it's almost the opposite. Just as species change over time, so does science. It changes not only with respect to its tenets and research tools, but also the way its propositions are received, criticized, regulated and debated by an audience far outside the community of those who practice it.
The evolution of evolutionary theory is no exception. Heated arguments between its advocates and those who believe in creationism or intelligent design are but blips in a massive, craggy landscape of controversy that has accumulated over two centuries.
More questions than we'd like were raised long ago, and remain unanswered. Two of the biggest: If humans are no different than animals, what is the status of free will, of morality borne from the brain, not the body? Can and should we apply ideas about the "survival of the fittest" to economics, to population control, to law, to love?
These gripping uncertainties spring from our common desire to eliminate uncertainty, or the unknowns of the surrounding universe, by subjecting them to knowledge, scrutiny and documentation. And as a result, we gamely hope that we'll stumble into some unequivocal truths about our place in the world, and why we are where we are.
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At this task, Darwin was king. His many diaries--some of the best reading around--are filled with vignettes parsing everyday occurrences. He thoughtfully recorded the patterns of his pets, children and neighbors; case studies his father, a doctor, recounted to him, along with stories of his own mind, body and travels. Within a few scribbled notebook entries, he refers to a dog closing a door, an orangutan pursing its lips with contempt and an older woman losing her memory. From these empirical scraps, he crafted a lofty hypothesis.
This idea of continuity between self and other, animal and human, past and present, is what gave Darwinian thinking its potency. Darwin practiced science in such a way that he tried to find reasons for both human exceptionalism and our commonalities with other living things. After all, what living thing on earth doesn't also nourish itself, reproduce and try its darndest to survive and succeed in an environment that changes faster than we possibly can?
Despite all this, these valiant attempts to explain our nature and how we fit into some larger narrative--what some call biological determinism--or any hint that biology is destiny--continue to spark wild controversy. Just look at the outcry stirred up when former Harvard President Larry Summers said that different degrees of "intrinsic aptitude" in math and science might be one reason there aren't as many female math and science professors in academia's upper echelons.
One hundred and fifty years later, biology's messy yet inextricable relationship with society isn't any more stable; the arguments are just couched in 21st-century vocabulary and duked out in the blogosphere rather than the front parlor.
Today, Darwinism is pervasive, its allusions gracing album titles, T-shirts, videogames and popular parlance. New terminology is often a translucent facade for age-old musings. For example, based on new data from the human genome project, or research on donor-conceived children like myself, just how much does biological knowledge equate to self-knowledge?
It's unsatisfying, certainly, but the answer is an amalgam of the following responses: A bit. A lot. Somewhat. We don't know. We're not sure. More than anything, we disagree. The only certainty is that, while the core principles of Darwinian theory have endured the trials of their first 150 years, the continuing evolution of its interpretation and application--when it comes to our ancestral origins and our future survival alike--promises to be anything but clear-cut.
Hana R. Alberts is the Opinions reporter at Forbes.
Parasites, ecosystems and sustainability:an ecological and complex systems perspective
Pierre Horwitza,*, Bruce A. Wilcoxb
aConsortium for Health and Ecology, Edith Cowan University, 100 Joondalup Drive, Joondalup, WA 6027, Australia
bAsia-Pacific Institute for Tropical Medicine and Infectious Diseases, John A. Burns School of Medicine, University of Hawaii, Honolulu 96822, Hawaii
Received 20 December 2004; received in revised form 16 March 2005; accepted 16 March 2005
Abstract
Host–parasite relationships can be conceptualised either narrowly, where the parasite is metabolically dependent on the host, or more
broadly, as suggested by an ecological–evolutionary and complex systems perspective. In this view Host–parasite relationships are part of a
larger set of ecological and co-evolutionary interdependencies and a complex adaptive system. These interdependencies affect not just the
hosts, vectors, parasites, the immediate agents, but also those indirectly or consequentially affected by the relationship. Host–parasite
relationships also can be viewed as systems embedded within larger systems represented by ecological communities and ecosystems. So
defined, it can be argued that Host–parasite relationships may often benefit their hosts and contribute significantly to the structuring of
ecological communities. The broader, complex adaptive system view also contributes to understanding the phenomenon of disease
emergence, the ecological and evolutionary mechanisms involved, and the role of parasitology in research and management of ecosystems in
light of the apparently growing problem of emerging infectious diseases in wildlife and humans. An expanded set of principles for integrated
parasite management is suggested by this perspective.
q 2005 Australian Society for Parasitology Inc. Published by Elsevier Ltd. All rights reserved.