24 de octubre de 2012

Scientists Read Dreams



Brain scans during sleep were successfully used to decode some of the visual content of subjects' dreams
Scientists have learned how to discover what you are dreaming about while you sleep.
A team of researchers led by Yukiyasu Kamitani of the ATR Computational Neuroscience Laboratories in Kyoto, Japan, used functional neuroimaging to scan the brains of three people as they slept, simultaneously recording their brain waves using electroencephalography (EEG).
The researchers woke the participants whenever they detected the pattern of brain waves associated with sleep onset, asked them what they had just dreamed about, and then asked them to go back to sleep.
This was done in three-hour blocks, and repeated between seven and ten times, on different days, for each participant. During each block, participants were woken up ten times per hour. Each volunteer reported having visual dreams six or seven times every hour, giving the researchers a total of around 200 dream reports.
Perchance to dream
Most of the dreams reflected everyday experiences, but some contained unusual content, such as talking to a famous actor. The researchers extracted key words from the participants’ verbal reports, and picked 20 categories — such as 'car', 'male', 'female', and 'computer' — that appeared most frequently in their dream reports.
Kamitani and his colleagues then selected photos representing each category, scanned the participants’ brains again while they viewed the images, and compared brain activity patterns with those recorded just before the participants were woken up.
The researchers analyzed activity in brain areas V1, V2 and V3, which are involved in the earliest stages of visual processing and encode basic features of visual scenes, such as contrast and the orientation of edges. They also looked at several other regions that are involved in higher order visual functions, such as object recognition.
In 2008, Kamitani and his colleagues reported that they could decode brain activity associated with the earliest stages of visual processing to reconstruct images shown to participants. Now, they have found that activity in the higher order brain regions could accurately predict the content of the participants’ dreams.
“We built a model to predict whether each category of content was present in the dreams,” says Kamitani. “By analyzing the brain activity during the nine seconds before we woke the subjects, we could predict whether a man is in the dream or not, for instance, with an accuracy of 75–80%.”
The findings, presented at the annual meeting of the Society for Neuroscience in New Orleans, Louisiana, earlier this week, suggest that dreaming and visual perception share similar neural representations in the higher order visual areas of the brain.
“This is an interesting and exciting piece of work,” says neuroscientist Jack Gallant at the University of California, Berkeley, of the work presented at the meeting. “It suggests that dreaming involves some of the same higher level visual brain areas that are involved in visual imagery.”
“It also seems to suggest that our recall of dreams is based on short-term memory, because dream decoding was most accurate in the tens of seconds before waking,” he adds.
Kamitani and his colleagues are now trying to collect the same kind of data from the rapid eye movement (REM) stage of sleep, which is also associated with dreaming. “This is more challenging because we have to wait at least one hour before sleeping subjects reach that stage,” Kamitani says.
But the extra effort will be worth it, he says. “Knowing more about the content of dreams and how it relates to brain activity may help us to understand the function of dreaming.”


18 de octubre de 2012

Nobel por la memoria celular



Robert J. Lefkowitz, de la Universidad de Duke, y Brian K. Kobilka, de la Universidad de Stanford, ambos de nacionalidad estadounidense, fueron galardonados con el Premio Nobel de Química 2012 por sus estudios de la familia de receptores acoplados a proteínas G, que forman parte de las células y les permiten estar en contacto con su entorno y adaptarse a los cambios, en una especie de memoria.

Estas proteínas vienen en pares, por lo el nombre dado por los científicos es Receptores Acoplado de Proteínas G (GPCR, por sus siglas en inglés).

Así, las proteínas G son uno de los componentes biomoleculares más importantes en un organismo vivo, pues se trata de las respuestas fisiológicas que permiten percibir, sentir, interpretar y vivir el entorno en un ser vivo.

En pocas palabras, las encargadas de responder como organismos vivos ante la realidad física.

Lefkowitz empezó a usar la radiactividad en 1968 aplicada a sus estudios de biología molecular. Concretamente, acopló un isótopo de iodina a varias hormonas y descubrió, entre otros, un receptor para la adrenalina, el beta-adrenérgico, que entre otras cosas interviene en la respuesta al estrés.

En 1980, Kobilka se incorporó al equipo para aislar el gen que codificaba este receptor. Descubrieron que era similar a otro existente en las células de la retina del ojo que son sensibles a la luz (rodopsina).

De esta manera, tanto la rodopsina como el beta-adrenérgico son GPCR.
Hoy se conocen cientos de miembros de esta familia de receptores, que son sensibles a la luz, el sabor, los olores, la adrenalina, la histamina, la dopamina (neurotransmisor del placer) o la serotonina (neurotransmisor del bienestar), entre otros estímulos.

A este fenómeno, el de activar varias respuestas fisiológicas, se le llama selección funcional.
Se estima que más del 50 por ciento de los medicamentos actuales tienen como diana receptores unidos a proteínas G.

17 de octubre de 2012

El origen de los sueños es un proceso de la memoria


Son los recuerdos almacenados en la mente junto al hipocampo cerebral los implicados en la formación de sueños.
Los sueños son recuerdos que aún no se han guardado es decir, recuerdos que se dispersan por distintas regiones cerebrales antes de ser almacenados en el cerebro. Los ensueños son procesos de memoria donde recuerdos e hipocampo son los componentes cerebrales involucrados en este procesamiento mental. Todo se basa en procesos de organización de la memoria humana.
En el cerebro, los sueños son procesos de la memoria
El funcionamiento del cerebro no cesa cuando uno duerme y prueba de ello son los sueños.
Los sueños son producto de procesos cerebrales donde se ven involucrados:
  • Memoria. El hipocampo es la parte del cerebro implicada en la actividad y formación de la memoria.
  • Recuerdos. Todo lo que una persona vive a diario forma parte del origen de las imágenes oníricas que se forman durante el sueño.
El proceso del sueño se inicia cuando el cuerpo comienza a descansar. Es durante ese momento cuando la conciencia abandona el cuerpo y uno pierde la noción de que está soñando.
 El funcionamiento o proceso de la memoria durante los sueños
Los ensueños parecen relacionarse con procesos de organización en la memoria de una persona donde la memoria adquirida durante días anteriores es reorganizada para poder ser guardada a largo plazo.
“Los recuerdos que se nos quedan prendidos en la memoria durante el día, pueden aparecer 5 ó 7 días más tarde en nuestros sueños” según afirma Tore Nielsen, quien ha denominado estos recuerdos tardíos como “el efecto del intervalo de los sueños”.
La memoria humana funciona a través de la asociación de ideas lo que significa que cuanto más vinculada esté una cosa con otra, más fácil será de recordar. Historias, pensamientos, emociones, sensaciones, sitios visitados… todo queda grabado en la memoria pero en los sueños no se reflejan tal y como fueron. Estas incoherencias que se revelan en los sueños son producto de la falla cerebral al querer integrar su propia información.

Tomado de: http://blogdefarmacia.com/el-origen-de-los-suenos-es-un-proceso-de-la-memoria/

15 de octubre de 2012

Memory Of Events Changes With Retelling


Researchers from the Feinberg School of Medicine at Northwestern University recently discovered that a memory of an event can change with each retelling.
The team of scientists found that the modification of the memory of an event is due to an adjustment in brain networks that changes the placement of the memory. As a result, when an individual remembers a particular situation, it may not be exactly the same as remembered before. The study by Northwestern is the first to examine this interaction in the brain. The findings were recently published in the Journal of Neuroscience.
“A memory is not simply an image produced by time traveling back to the original event — it can be an image that is somewhat distorted because of the prior times you remembered it,” explained lead author Donna Bridge, a postdoctoral fellow at Northwestern University Feinberg School of Medicine, in a prepared statement. “Your memory of an event can grow less precise even to the point of being totally false with each retrieval.”
The results of the study may pinpoint some of the issues that witnesses may have when giving a testimony for a trial.
“Maybe a witness remembers something fairly accurately the first time because his memories aren’t that distorted,” noted Bridge in the statement. “After that it keeps going downhill.”
It also shows that human memories have a way of adapting through time.
“When someone tells me they are sure they remember exactly the way something happened, I just laugh,” commented Bridge in the statement.
In the study, a group of participants were given the task of recalling the placement of objects on a grid over a three-day period of three separate sessions. In the first session, participants studied the placement of 180 object-location associations on a computer screen. In the next session, they took a recall test where they had to place the objects in the original location. The last session was a final recall exam. Researchers discovered that the recall of the individuals was never exactly perfect and, during the second recall test, they placed the objects closer to the incorrect location than the first recall test.
“Memories aren’t static,” remarked Bridge in the statement. “If you remember something in the context of a new environment and time, or if you are even in a different mood, your memories might integrate the new information.”
The researchers also looked at the neural signals in the brain to better understand the electrical activity in the brain. In particular, the scientists wanted to know if the neural signals in the second test correlated to the results of the first recall test. They found that there was a stronger neural signal during the first recall test as opposed to during the second recall test.
“The strong signal seems to indicate that a new memory was being laid down,” mentioned Bridge in the statement. “And the new memory caused a bias to make the same mistake again.”
The study was funded by the National Science Foundation, National Institute of Neurological Disorders, and the National Institutes of Health.
“This study shows how memories normally change over time, sometimes becoming distorted,” proposed Ken Paller, a professor of Brain, Behavior, and Cognition at Northwestern, in the statement. “When you think back to an event that happened to you long ago — say your first day at school — you actually may be recalling information you retrieved about that event at some later time, not the original event.”

2 de octubre de 2012

Sentient Skills Science: What Makes Some Memories So Memorable?


An unforgettable activity from Scientific American. 
By Daisy Yuhas


Key concepts

Memory
Neuroscience
Psychology
Graphing

Introduction

Have you ever tried to remember an entire list of groceries—without looking at the written list while you're shopping? Even a master of memory skills may fail to recall an item or two. But why does this happen? In this activity you will learn a little more about memory— how it works and what factors make some details more memorable than others. You will also re-create a psychology experiment that helped scientists identify two effects that can distinctly shape what we remember.

Background

Can you recall all of the words in the paragraph above? No peeking! Some memories are stored for only short periods of time before they disappear. You need to remember the beginning of a sentence to understand the end, for example, but might not need to retain each sentence word-for-word to understand the whole paragraph. This briefly held form of recollection is called short-term memory. Other memories, however, last much longer. Scientists believe that a seahorse-shaped structure in the brain called the hippocampus helps us transform our memories from short- to long-term.

Another form of recollection is working memory. This is what helps you remember and juggle information that is involved in tasks in which you are engaged. This is the form of memory that lets you perform mental math, conjugate verbs or put together a list. Scientists have found that an area of your brain right behind your temples, called the prefrontal cortex, helps you carry out working memory tasks.

Materials
•    Pencils
•    Paper, preferably lined or graph paper
•    Watch or clock (optional)
•    Gather a group of friends and family to be your subjects—at least five people (but the bigger the group, the better your results)

Preparation
•    Give each of your subjects a piece of paper and pencil.
•    Ask your subjects to listen carefully as you list 20 words. They will need to remember as many as they can but not write anything down until you tell them to.

Procedure

  • In a steady, even pace—about one word every second if you are using a clock or watch—read the following list of words in order: home, dog, rock, hand, table, card, bag, monkey, phone, cookie, mouse, paper, nail, hat, pillow, water, juice, watch, circle and glass.
  • Why do you think your pacing matters? What do you think might happen if you repeated this activity and read more slowly? What if you read more quickly?
  • When you have finished reading the list, pause for one more second and then ask your subjects to write down as many words as they can remember.
  • Collect their lists and on a fresh piece of paper and prepare a line graph. The vertical y-axis of the graph will represent the number of subjects in your study. Starting at the bottom of this axis, write the number 1, then evenly space consecutive numbers until you have reached the total number of subjects in your experiment. If five friends participated, you will have the numbers 1 through 5 going up this axis.
  • The horizontal x-axis of your graph will include the words on your original list. Write these out, evenly spaced, in the same order that you read them. Your line graph will now allow you to pinpoint how many subjects remembered each of the words on the list.
  • Count up how many subjects correctly remembered each word. Above each word on your graph's x-axis, mark a dot that corresponds with the number of subjects along the y-axis. Are there certain words that everyone remembered? Are there words that all of your subjects forgot? Do some people have much sharper memories than others?
  • When you have placed a dot for each word, connect these points. Do you notice any patterns? Does your line graph have a smooth shape or is it spiky? Why do you think certain words were more memorable than others?
  • Extra: In the original list, all of the words are simple and concrete, making them easier to imagine and relate to. Repeat this experiment with a new list of short, common words but include some that are idea-based, or abstract. You could also read a list of real and made-up words. Are certain words harder to remember than others?
  • Extra: Distract your subjects by adding a working memory challenge at the end of the experiment. Repeat the above activity with a new list, but before your subjects write anything down, ask them to recite the last 10 letters of the alphabet backward. Then let your subjects write down as many from the original list as they can remember. Graph and compare your results. Does disrupting memory change the pattern of remembered words?
  • Extra: You can also try to enhance memory. First, strategize with your subjects on good memory techniques. For example, many people find that visualizing something makes it easier to remember. Try a few examples as a group, then repeat the experiment with a new set of words. Did your subjects remember more words with a little coaching?


Observations and Results

Did most people remember the first and last words on the list, but forget those in the middle?

Most people who try this experiment find their results create a U-shaped line graph. That means people do a good job remembering the beginning and end of the list, but struggle to recall words in the middle. Two different memory effects create this pattern. The primacy effect suggests that we are good at remembering the very first information we encounter. Scientists are still unsure exactly how this effect works, but one theory is that individuals trying to remember words will repeat the growing list each time a new term is added. As a result, they repeat the first few items more than any other and this repetition shifts information from the short-term to more secure long-term memory. The second effect is the recency effect. This suggests it's easier to remember what we learned last because it is still fresh in our minds. If these theories are correct, your working memory, which is trying to reassemble the list of words, struggles to recall terms in the middle because they haven't yet been stored in long-term memory and have been pushed out of short-term memory by more recent additions.

If you've ever written a book report, you may have encountered both of these effects—it's easy to remember how a book ends and you can probably recall how it began, but the middle gets muddled. Luckily, once you have recognized these effects you can also find ways to overcome them. In the case of that book report, taking extra notes is a simple solution that helps your memory keep details straight.

Recency and primacy are not the only effects that can influence your memory. You may have noticed that some words from the middle of the list were still very memorable. This could be because the words had special significance. For example, if a phone rang as you read "phone" or your subjects were very hungry when you said "cookie," these words could have gained added meaning.

More to explore
How does short-term memory work in relation to long-term memory? from Scientific American
Memory Experiments from Eric H. Chudler's Neuroscience for Kids
Memory and Learning from Bruno Dubuc, McGill University
Mapping Memory in 3-D from National Geographic
How Human Memory Works from HowStuffWorks.com
Working Memory from Thinker: A Cognitive Psychology Resource


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