domingo, 5 de diciembre de 2010

A Street of Puzzles

WINDOWS ON THE WORLD

A Street of Puzzles

A series in which writers from around the world describe the view from their windows.
When my writing is not going well, there are two things I do in the hope of luring the words back: I read some pages of books I love or I watch the world. This is my view when I am at home in Nigeria, in the port city of Lagos. An ordinary view, with houses close together, cars crammed in corners, each compound with its own gate, little kiosks dotting the street. But it is a view choked with stories, because it is full of people. I watch them and I imagine their lives and invent their dreams.
The stylish young woman who sells phone cards in a booth next door, the Hausa boys who sell water in plastic containers, stacked in wheelbarrows. The vendor with a pile of newspapers, pressing his horn, his hopeful eyes darting up to the verandas. The bean-hawker who prowls around in the mornings, calling out from time to time, a large pan on her head. The mechanics at the corner who buy from her, often jostling one another, often shirtless, and sometimes falling asleep under a shade in the afternoon.
I strain to listen to their conversations. Once I saw two of the mechanics in a raging but brief fight. Once I saw a couple walk past holding hands, not at all a common sight. Once, a young girl in a blue school uniform, hair neatly plaited, looked up and saw me, a complete stranger, and said, “Good morning, ma,” curtsying in the traditional Yoruba way, and it filled me with gladness. The metal bars on the window — burglary-proof, as we call it — sometimes give the street the air of a puzzle, jagged pieces waiting to be fit together and form a whole.
— Chimamanda Ngozi Adichie
Chimamanda Ngozi Adichie is the author, most recently, of “The Thing Around Your Neck.” Matteo Pericoli, an artist, is the author of “The City Out My Window: 63 Views on New York.”

Site for Teenagers With Literary Leanings

Web Site for Teenagers With Literary Leanings

Enlarge This ImageWhen Jacob Lewis helped create the beta version of the Web siteFigment with Dana Goodyear, a staff writer at The New Yorker, Mr. Lewis envisioned it as a sort of literary Facebook for the teenage set.
Chester Higgins Jr./The New York Times
Jacob Lewis, one of the founders of Figment.com.
“I really went into it and thought, ‘We’ll be the social network for young-adult fiction,’ ” said Mr. Lewis, a former managing editor of The New Yorker. “But it became clear early on that people didn’t want a new Facebook.”
The young people on the site weren’t much interested in “friending” one another. What they did want, he said, “was to read and write and discover new content, but around the content itself.”
Figment.com will be unveiled on Monday as an experiment in online literature, a free platform for young people to read and write fiction, both on their computers and on their cellphones. Users are invited to write novels, short stories and poems, collaborate with other writers and give and receive feedback on the work posted on the site.
The idea for Figment emerged from a very 21st-century invention, the cellphone novel, which arrived in the United States around 2008. That December, Ms. Goodyear wrote a 6,000-word article for The New Yorker about young Japanese women who had been busy composing fiction on their mobile phones. In the article she declared it “the first literary genre to emerge from the cellular age.”
Figment is an attempt to import that idea to the United States and expand on it. Mr. Lewis, who was out of a job after Portfolio, the Condé Nast magazine, was shuttered last year, teamed up with Ms. Goodyear, and the two worked with schools, libraries and literary organizations across the country to recruit several hundred teenagers who were willing to participate in a prototype, which went online in a test version in June.
“We wanted people to be able to write whatever they wanted in whatever form they wanted,” Mr. Lewis said. “We give them a piece of paper and say, ‘Go.’ ” He added that so far contributions had included fantasy, science fiction, biographical work and long serial novels. “There’s a very earnest and exacting quality to what they’re doing.”
Teenagers and their reading habits have been the subject of much fascination in the publishing industry lately. They were a huge driving force behind best-selling books like the “Twilight” series by Stephenie Meyer and the crop of paranormal-romance books that followed. Publishers are eager to learn more about their reading habits and introduce books to them.
Mr. Lewis said he hoped Figment would eventually attract more than a million users and serve as an opportunity for publishers to roam the Web site looking for fresh young talent, or promote their own authors by running book excerpts. “For publishers this is an amazing opportunity to not only reach your consumers but to find out really valuable information about how they are reading,” he said.
Several publishers have already signed on. Running Press Kids, a member of the Perseus Books Group, will provide an excerpt from “Purple Daze,” a historical novel for teenagers written by Sherry Shahan. (Figment charges a small fee to publishers for the privilege.)
David Steinberger, the chief executive of Perseus, said he saw Figment as an opportunity to get the company’s content in front of teenagers.
“The teen culture is a constantly moving target,” Mr. Steinberger said. “We’re looking for partners who are deeply embedded in the way teens interact.”

Profilaxis de la úlcera de estrés: revisión sistemática y metaanálisis


REMI envía todos sus contenidos gratuitamente por correo electrónico a más de 8.600 suscriptores. [Suscripción]
Artículo nº 1579. Vol 12, diciembre 2010.
Autor: Belén Quesada Bellver

Profilaxis de la úlcera de estrés: revisión sistemática y metaanálisis

Artículo original: Stress ulcer prophylaxis in the new millennium: a systematic review and meta-analysis. Marik PE, Vasu T, Hirani A, Pachinburavan M. Crit Care Med 2010; 38(11): 2222-2228. [Resumen] [Artículos relacionados]

Introducción: La profilaxis de la úlcera de estrés es una práctica universalmente extendida [1] y forma parte de los paquetes de medidas en el paciente crítico. Sin embargo, actualmente esta patología es un evento relativamente infrecuente en nuestras Unidades y el riesgo de sangrado clínicamente significativo es bajo [2]. Dicho tratamiento no está exento de riesgos, tales como la modificación del pH gástrico (favoreciendo la colonización y crecimiento de microorganismos), mayor riesgo de neumonía nosocomial [3] e interacciones medicamentosas, además de tener sus efectos secundarios específicos. Por otro lado, distintos estudios han sugerido que la nutrición enteral (NE) precoz reduce el riesgo de úlcera de estrés. Los autores realizaron esta revisión pensando que la profilaxis del ulcus podría no aportar ningún beneficio en los pacientes con NE, e incluso ser perjudicial en términos de morbimortalidad.

Resumen: Se incluyeron 17 estudios controlados y aleatorizados (1.836 pacientes) en que se comparaban inhibidores de receptores H2 de histamina contra placebo. En general, la profilaxis redujo el riesgo de sangrado gastrointestinal, aunque este efecto sólo se vio en el subgrupo de pacientes sin NE. En los pacientes con NE la profilaxis no disminuyó el riesgo de sangrado. La incidencia de neumonía nosocomial no fue mayor en pacientes con profilaxis, aunque esta complicación sí se observó con más frecuencia en los pacientes con NE. Aunque la profilaxis de úlcera de estrés no tuvo efecto sobre la mortalidad, los pacientes con nutrición enteral y que recibieron profilaxis presentaron mayor mortalidad hospitalaria.

Comentario: Salvando los inconvenientes de toda revisión o metanálisis, los datos sugieren que en pacientes que toleran adecuadamente la NE, la profilaxis de úlcera de estrés podría no ser necesaria e incluso favorecería el riesgo de neumonía y muerte; la combinación de profilaxis de úlcera y nutrición enteral eleva el pH gástrico y el riesgo de colonización gástrica más que cualquiera de las dos intervenciones por separado. Dado que la profilaxis de la úlcera de estrés está considerada como indicador de calidad, es necesario reevaluar la eficacia y seguridad de esta medida en pacientes con y sin nutrición enteral.
Belén Quesada Bellver
Hospital Fundación Jiménez Díaz, Madrid
©REMI, http://remi.uninet.edu. Diciembre 2010.

Enlaces:
  1. Prevention of stress ulceration: current trends in critical care. Daley RJ, Rebuck JA, Welage LS, Rogers FB. Crit Care Med 2004; 32(10): 2008-2013. [PubMed]
  2. Clinically significant gastrointestinal bleeding in critically ill patients with and without stress-ulcer prophylaxis. Faisy C, Guerot E, Diehl JL, Iftimovici E, Fagon JY. Intensive Care Med 2003; 29(8): 1306-1313. [PubMed]
  3. Acid-suppressive medication use and the risk for hospital-acquired pneumonia. Herzig SJ, Howell MD, Ngo LH, Marcantonio ER. JAMA 2009; 301: 2120-2128. [PubMed]
Búsqueda en PubMed:
  • Enunciado: Profilaxis de la úlcera de estrés, nutrición enteral, inhibidores de la bomba de protones y antagonistas de los receptores H2 de la histamina
  • Sintaxis: stress ulcer prophylaxis AND (histamine receptor blocker OR proton pump inhibitor) AND enteral nutrition
  • [Resultados]
Palabras clave: Profilaxis de la úlcera de estrés, Antagonistas de los receptores H2 de la histamina, Inhibidores de la bomba de protones, Nutrición enteral, Neumonía nosocomial, Cuidados Intensivos.

Doctor Faces Suits Over Cardiac Stents

Doctor Faces Suits Over Cardiac Stents

Word quickly reached top executives at Abbott Laboratories that a Baltimore cardiologist, Dr. Mark Midei, had inserted 30 of the company’s cardiac stents in a single day in August 2008, “which is the biggest day I remember hearing about,” an executive wrote in a celebratory e-mail.
Two days later, an Abbott sales representative spent $2,159 to buy a whole, slow-smoked pig, peach cobbler and other fixings for a barbecue dinner at Dr. Midei’s home, according to a report being released Monday by the Senate. The dinner was just a small part of the millions in salary and perks showered on Dr. Midei for putting more stents in more patients than almost any other cardiologist in Baltimore.
The Senate Finance Committee, which oversees Medicare, started investigating Dr. Midei in February after a series of articles in The Baltimore Sun said that Dr. Midei at St. Joseph Medical Center, in Towson, Md., had inserted stents in patients who did not need them, reaping high reimbursements from Medicare and private insurance.
The senators solicited 10,000 documents from Abbott and St. Joseph. Their report, provided in advance to The New York Times, concludes that Dr. Midei “may have implanted 585 stents which were medically unnecessary” from 2007 to 2009. Medicare paid $3.8 million of the $6.6 million charged for those procedures.
The report also describes the close relationship between Dr. Midei and Abbott Labs, which paid consulting fees to the cardiologist after he left the hospital. “The serious allegations lodged against Dr. Midei regarding the medically unnecessary implantation of cardiac stents did not appear to deter Abbott’s interest in assisting him,” the report states.
The case has turned into a legal quagmire for Dr. Midei and St. Joseph, which have been sued by hundreds of patients who claim they received unnecessary implants. Some doctors say the case has revealed a level of inappropriate care that is more common than most patients know.
“What was going on in Baltimore is going on right now in every city in America,” said Dr. Steven Nissen, chief of cardiovascular medicine at the Cleveland Clinic, who said he routinely treats patients who have been given multiple unneeded stents. “We’re spending a fortune as a country on procedures that people don’t need.”
Dr. Midei’s lawyer, Stephen L. Snyder, said that his client’s treatment of his patients was entirely appropriate and that Dr. Midei, who has recently practiced medicine at the Prince Salman Heart Center in Saudi Arabia, would be exonerated.
“This is all trumped up to hide the hospital’s criminal conduct,” said Mr. Snyder, who filed a $60 million lawsuit against St. Joseph on Dr. Midei’s behalf accusing the hospital of damaging Dr. Midei’s reputation by making false claims about his care. (The hospital responded that the assessments of Dr. Midei’s care were done by independent experts.)
Last month, St. Joseph agreed to pay a $22 million fine to settle charges that it paid illegal kickbacks to Dr. Midei’s medical practice, MidAtlantic Cardiovascular Associates, in exchange for patient referrals; the hospital did not admit wrongdoing. St. Joseph said in a statement Friday that it now conducts monthly random reviews of stent cases “to assure such a situation cannot occur again.”
As for Abbott Labs, a spokesman wrote in an e-mail that its affiliation with Dr. Midei ended early this year. “Dr. Midei has been a highly regarded physician in his field, with whom Abbott had consulted in the past,” said the spokesman, Jonathan Hamilton. “We have no further comment at this time.”
The case has had wide repercussions. Over the past year, St. Joseph has told hundreds of Dr. Midei’s patients that they did not need the expensive and potentially dangerous stents that the doctor inserted because their arteries were not as obstructed as he had claimed. Now, state health officials are investigating other local cardiologists who inserted a suspiciously high number of stents, which are tiny wire mesh devices inserted to prop open clogged arteries in the heart.
After reports about the Midei case and the wider state investigation, the number of stent procedures performed at St. Joseph and other area hospitals plunged, raising doubts about the appropriateness of much of the region’s cardiac care.
A landmark 2007 study published in The New England Journal of Medicine showed that many patients given stents would fare just as well without them. Dr. Christopher J. White, president-elect of the Society for Cardiovascular Angiography and Interventions, said that inappropriate stenting was a problem, but a rare one. The federal Medicare program spent $3.5 billion last year on stent procedures
Prosecutors, malpractice lawyers and state medical boards are only now waking up to the issue. The Texas Medical Board last month accused a widely known cardiologist in Austin of inserting unnecessary stents. In September, federal prosecutors accused a cardiologist in Salisbury, Md., of performing unnecessary stent surgeries, and last year a Louisiana doctor was sentenced to 10 years in prison for inserting unneeded stents.
J. Stephen Simms, a Baltimore lawyer who successfully pursued a federal whistle-blower lawsuit involving kickbacks for coronary procedures, said such cases were “the flavor of the month right now” with federal prosecutors.
Jay Miller, another Baltimore lawyer, said he was devoting his entire practice to unnecessary stent cases. “And I don’t think this is limited to just a few Maryland hospitals,” Mr. Miller said.
But far from questioning cardiologists who perform an unusually high number of stent procedures, many hospital executives celebrate these doctors because of the revenue they bring, which can be more than $10,000 per procedure.
“Hospital patients expect their care to be based on medical need, not profits,” said SenatorMax Baucus, Democrat of Montana and chairman of the Finance Committee. “Even more disconcerting is that this could be a sign of a larger national trend of wasteful medical device use.”
Dr. Midei’s fall was as rapid as it was dramatic. In a June deposition for a lawsuit against him, he said: “I didn’t know what hit me. I was bewildered by what had happened.”
He had been one of the most sought-after clinicians in his region. Trained at Johns Hopkins University, he was a co-founder of MidAtlantic, a practice with dozens of cardiologists that controlled much of the cardiac business in Baltimore’s private hospitals. Dr. Midei was one of the practice’s stars. When MidAtlantic negotiated a $25 million merger with Union Hospital in 2007, the deal was contingent on his continued employment.
St. Joseph was so concerned about losing Dr. Midei’s business that the hospital offered a $1.2 million salary if he would leave MidAtlantic and join the hospital’s staff. When Dr. Midei agreed, the merger with Union collapsed, MidAtlantic sued, and the practice’s former chief executive vowed in a deposition to “spend the rest of my life trying to destroy him personally and professionally.”
In the June deposition, Dr. Midei estimated that in 2005 — before research revealed that many stents were unnecessary — he performed about 800 stent procedures. Instead of dropping in subsequent years, however, the number of stents Dr. Midei inserted rose to as many as 1,200 annually, he estimated. In a 2007 internal document, Abbott Laboratories ranked Dr. Midei’s use of stents behind only five other cardiologists in the Northeast, including those at hospitals four and five times St. Joseph’s size.
That sort of increase in volume was an obvious red flag, said Dr. William E. Boden, clinical chief of the division of cardiovascular medicine at the University of Buffalo and an author of the 2007 stent study. “For him to have this brisk increase over those years is really unusual,” Dr. Boden said.
In stable patients, stents should be used only if X-rays show that most of the artery is blocked, and the patient has symptoms like frequent chest pain. Stent procedures can, in rare cases, cause bleeding, stroke or a heart attack. Once a stent is placed, it can result in a life-threatening clot that emerges weeks to months later. Stent patients must spend a year or more taking blood-thinning medications, which have their own risks.
In April 2009, a patient of Dr. Midei’s who was also a St. Joseph employee complained that he had received an unneeded stent and that many other patients had as well. The hospital engaged a panel of experts who reviewed 1,878 cases from January 2007 to May 2009 and found that 585 patients might have received unnecessary stents.
When asked to review the cases himself, Dr. Midei found far less blockage than he had initially, according to the Maryland Board of Physicians. The hospital suspended his privileges and eventually sent letters to all 585 patients. Hundreds of lawsuits against Dr. Midei and St. Joseph followed, including from patients treated well before January 2007.
Abbott responded to the controversy by hiring Dr. Midei as a consultant. “It’s the right thing to do because he helped us so many times over the years,” an Abbott executive wrote in a January e-mail cited in the Senate report.
The company sent Dr. Midei to Japan, but news of the controversy made his duties impossible, and he flew home. After one particularly critical story in The Baltimore Sun, David C. Pacitti, an Abbott executive, wrote in an e-mail, “Someone needs to take this writer out and kick his ass!”
Edward Chaid, 68, a semiretired general contractor from Timonium, Md., is among those who have sued. Five years ago, Mr. Chaid decided to get his first physical examination in decades. Just to be safe, his doctor sent him for a cardiac stress test at MidAtlantic, which revealed a small “squiggle” of concern, Mr. Chaid said. He was sent to Dr. Midei to get his arteries X-rayed, and he emerged from the procedure with two stents.
“Dr. Midei said: ‘You sure are lucky. You had 90 percent blockage.’ And the nurse said, ‘Oh yeah, you were blocked in your widow-maker.’ And I said: ‘Thank God. I guess I’m really lucky you got it when you did,’ ” Mr. Chaid said in an interview.
Five years later, another doctor concluded that Mr. Chaid’s blockage had been minimal. “I was really shocked,” Mr. Chaid said. “I’m from a generation where doctors are thought very highly of.”
But Mr. Snyder, Dr. Midei’s lawyer, said that his client’s care had been entirely appropriate, that doctors often interpret X-rays differently and that St. Joseph was using him as a scapegoat. A Web site created by friends of Dr. Midei lists dozens of testimonials like this one: “Plain and simple, Dr. Midei saved my life.”

Manejo anestésico de una paciente con obesidad mórbida, en posición prona para cirugía de columna lumbar


Manejo anestésico de una paciente con obesidad mórbida, en posición prona para cirugía de columna lumbar
Una mujer con obesidad mórbida, de 45 años de edad, con un índice de masa corporal de 47 kg / m 2, se presentó con un disco intervertebral prolapsado de la columna lumbar para la descompresión y la fijación. La anestesia y la colocación quirúrgica de los pacientes con obesidad mórbida lleva tres peligros principales, a saber, la obesidad mórbida, la posición boca abajo, y los problemas de las vías respiratorias. La obesidad mórbida tiene sus propios peligros de la trombosis venosa profunda y embolia pulmonar. Aquí se describe el manejo anestésico, afrontar con éxito los problemas específicos de este paciente debido a la obesidad.


Anesthesia management of a morbidly obese patient in prone position for lumbar spine surgery
V Baxi, S Budhakar
Lilavati Hospital and Research Centre, Mumbai, India,
J Craniovert Jun Spine 2010:1:55-57.
A morbidly obese, 45-year-old woman with a body mass index of 47 kg/m 2 , presented with a prolapsed intervertebral disc of the lumbar spine for decompression and fixation. Anesthesia and surgical positioning of morbidly obese patient carries 3 main hazards, namely, morbid obesity, prone position, and airway preservation problems. Morbid obesity has its own hazards of deep vein thrombosis and pulmonary embolus. Here we describe anesthetic management, successfully dealing with the specific problems of this patient due to obesity

sábado, 4 de diciembre de 2010

Inversiones

El futuro inmediato de la rehabilitación es virtual

CON BIOELECTRÓNICA, REALIDAD AUMENTADA, IMAGEN...

El futuro inmediato de la rehabilitación es virtual

La realidad virtual, la realidad aumentada, la bioelectrónica, la imagen médica, la inteligencia ambiental o las interfaces naturales entre hombre y máquina conforman el futuro indiscutible de la rehabilitación.
Gorka Artaza. Las Palmas - Martes, 22 de Junio de 2010 - Actualizado a las 00:00h.
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Inmaculada García Montes, presidenta de Sermef.
Inmaculada García Montes, presidenta de Sermef.
Las nuevas tecnologías se están incorporando a gran velocidad al sistema sanitario. Uno de los sectores que más beneficios ve en su utilización es el de la rehabilitación. El principal reto que se han marcado los médicos rehabilitadores de cara al futuro inmediato es la implantación de la rehabilitación virtual: "Mediante nuevas tecnologías, gráficas interactivas y de telecomunicación, podremos ofrecer servicios clínicos de rehabilitación y tele-rehabilitación de forma más eficaz y eficiente", señala Inmaculada García Montes, presidenta de la Sociedad Española de Rehabilitación y Medicina Física (Sermef).
Los médicos rehabilitadores pretenden lograr mejores terapias para los pacientes y que, a la vez, "sean sostenibles para los servicios de salud".
  • Laboratorios de biomecánica para patologías tan comunes como la cervicalgia y la lumbalgia serán imprescindibles en la recuperación
Tecnologías
Los especialistas en la recuperación de pacientes basarán este área multidisciplinar en tecnologías como la realidad virtual, la realidad aumentada, la bioelectrónica, la imagen médica, la inteligencia ambiental o las interfaces naturales entre hombre y máquina.
Además, la medicina física y la rehabilitación apuestan por modernizar sus servicios con el objetivo de otorgar un mejor y más precoz diagnóstico.
Laboratorios de biomecánica para patologías tan comunes como la cervicalgia, lumbalgia o para un correcto análisis de la marcha de un paciente amputado, ecografías para musculoesquelético, termografía por infrarrojos o electromiografía, son sólo algunos de los instrumentos que ayudarán a los especialistas en este trabajo.
"Todos estos avances son muy importantes en una especialidad que se ocupa de atender, de por vida, al paciente con dolor crónico de aparato locomotor, como el paciente con una gran discapacidad tipo paraplejia o daño cerebral; la aplicación de estas tecnologías puede suponer toda una revolución", afirma García Montes.
Otro de los retos que se plantea la especialidad es aumentar el número de unidades específicas de neurorehabilitación, un aspecto fundamental "al ser ésta una especialidad con presencia en todos los niveles de la sanidad, tanto de hospitales de nivel 3 como en atención primaria, pasando por todos los hospitales comarcales", afirma la presidenta de la Sermef.
Trabajo en equipo
Los especialistas consideran imprescindible un "trabajo en equipo multidisciplinar con el médico rehabilitador a la cabeza, así como continuar con nuestra progresiva presencia en atención primaria a método de prevención, diágnostico y tratamiento de las diferentes patologías".
La Sermef ha celebrado su XLVIII Congreso Nacional en Las Palmas de Gran Canaria. Durante cuatro días, más de 650 especialistas han debatido sobre las últimas novedades de la especialidad, basándose principalmente en los tres temas clave del congreso: artrosis, osteoporosis y disfunciones de suelo pélvico.

Artículo original

9/nov/2010 Schizophrenia Bulletin. 2009 Jul;35(4):668-674.

De los acontecimientos del mundo real a la psicosis: La nueva neurofarmacología de las ideas delirantes.

(From Real-World Events to Psychosis: The Emerging Neuropharmacology of Delusions.)
Autor-es: Paul D. Morrison; R.M. Murray.
Puntuación: 5,5/10 (2 votos) votar - leído 543 veces - comentar
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Resumen

Las primeras fases de las ideas delirantes se caracterizan por una sobreabundancia de coincidencias significativas que se imponen a la visión del mundo existente de quien las sufre. Esta persona ve que los acontecimientos sucesivos señalan hacia una nueva realidad que le concierne y se apodera de su vida cotidiana, y posteriormente confirman dicha realidad.

La investigación en las últimas cuatro décadas ha mostrado la importancia de los receptores dopamínicos (DA) D2 y de los ganglios basales en el pensamiento psicótico. Trabajos recientes han implicado al aprendizaje con recompensa anómala iniciado por el exceso de liberación de DA en la atribución de una importancia excesiva o «saliencia» a estímulos y acontecimientos insignificantes. Pero nuestro conocimiento de lo que ocurre más allá de los receptores D2 es escaso. Esta laguna es evidente especialmente a los niveles celular y de microcircuitos, e incluye cambios plásticos, que se piensa que son esenciales para el nuevo aprendizaje, y cuyos procesos pueden ir mal en las principales enfermedades mentales.

Actualmente los nuevos hallazgos farmacológicos están mejorando nuestro conocimiento del procesamiento de la información y del aprendizaje en el estriado. La DA tiene una función importante en el ajuste de la solidez de las conexiones individuales del estriado, aunque no actúa de forma aislada.

Hay otros dos sistemas motivadores que son críticos, los endocannabinoides y la adenosina. Por lo tanto, en las neuronas espinosas medias que pertenecen a la vía indirecta, la estimulación de los receptores D2 evoca una depresión de las aferencias corticales mediada por los endocannabinoides. La acción de la adenosina sobre los receptores A2A produce el efecto contrario.

Se debe señalar que los fármacos que actúan sobre los sistemas de los endocannabinoides y purinérgico también tienen propiedades propsicóticas o antipsicóticas. En este artículo analizamos cómo los tres moduladores regulan el aprendizaje en el estriado y cómo su disfunción puede dar lugar a pensamiento delirante.



Abstract

The earliest stages of delusion are characterized by an overabundance of meaningful coincidences impinging on the sufferer's existing worldview. Successive events are seen by him as pointing to, and then confirming, a fundamentally new reality that takes him over and engulfs his everyday life. Research over the last 4 decades has revealed the importance of dopamine (DA), D2 receptors, and the basal ganglia in psychotic thinking.

Recent work has implicated the aberrant reward learning initiated by the excess release of striatal DA in the attribution of excessive importance or “salience” to insignificant stimuli and events. But our knowledge of what is happening beyond D2 receptors has remained scant. The gap is especially apparent at the cellular and microcircuit levels, encompassing the plastic changes, which are believed to be essential for new learning, and whose processes may go awry in major mental illness.

Now new pharmacological findings are advancing our understanding of information processing and learning within the striatum. DA has an important role in setting the strength of individual striatal connections, but it does not act in isolation. Two other modulator systems are critical, the endocannabinoids and adenosine.

Thus, at medium spiny neurons belonging to the indirect pathway, D2 stimulation evokes endocannabinoid-mediated depression of cortical inputs. Adenosine acting at A2A receptors elicits the opposite effect. Remarkably, drugs that target the endocannabinoid and purinergic systems also have pro- or antipsychotic properties. Here, we discuss how the 3 modulators regulate learning within the striatum and how their dysfunction may lead to delusional thinking.

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