Psychologists document the age our earliest memories fade

Although infants use their memories to learn new information, few adults can remember events in their lives that happened prior to the age of three. Psychologists have now documented that age seven is when these earliest memories tend to fade into oblivion, a phenomenon known as "childhood amnesia." The study is the first empirical demonstration of the onset of childhood amnesia, and involved interviewing children about past events in their lives.

What's your earliest surviving memory?

Although infants use their memories to learn new information, few adults can remember events in their lives that happened prior to the age of three. Psychologists at Emory University have now documented that age seven is when these earliest memories tend to fade into oblivion, a phenomenon known as "childhood amnesia."

The journal Memory published the research, which involved interviewing children about past events in their lives, starting at age three. Different subsets of the group of children were then tested for recall of these events at ages five, six, seven, eight and nine.

"Our study is the first empirical demonstration of the onset of childhood amnesia," says Emory psychologist Patricia Bauer, who led the study. "We actually recorded the memories of children, and then we followed them into the future to track when they forgot these memories."

The study's co-author is Marina Larkina, a manager of research projects for Emory's Department of Psychology.

The Bauer Memory Development Lab focuses on how episodic, or autobiographical memory, changes through childhood and early adulthood.

"Knowing how autobiographical memory develops is critically important to understanding ourselves as psychic beings," Bauer says. "Remembering yourself in the past is how you know who you are today."

Scientists have long known, based on interviews with adults, that most people's earliest memories only go back to about age 3. Sigmund Freud coined the term "childhood amnesia" to describe this loss of memory from the infant years. Using his psychoanalytic theory, Freud made the controversial proposal that people were repressing their earliest memories due to their inappropriate sexual nature.

In recent years, however, growing evidence indicates that, while infants use memory to learn language and make sense of the world around them, they do not yet have the sophisticated neural architecture needed to form and hold onto more complex forms of memory.

 

Instead of relying on interviews with adults, as previous studies of childhood amnesia have done, the Emory researchers wanted to document early autobiographical memory formation, as well as the age of forgetting these memories.

The experiment began by recording 83 children at the age of three, while their mothers or fathers asked them about six events that the children had experienced in recent months, such as a trip to the zoo or a birthday party.

"We asked the parents to speak as they normally would to their children," Bauer says.

She gives a hypothetical example: "The mother might ask, 'Remember when we went to Chuck E. Cheese's for your birthday party?' She might add, 'You had pizza, didn't you?'"

The child might start recounting details of the Chuck E. Cheese experience or divert the conversation by saying something like, "Zoo!"

Some mothers might keep asking about the pizza, while another mother might say, "Okay, we went to the zoo, too. Tell me about that."

Parents who followed a child's lead in these conversations tended to elicit richer memories from their three-year-olds, Bauer says. "This approach also related to the children having a better memory of the event at a later age."

After recording these base memories, the researchers followed up with the children years later, asking them to recall the events that they recounted at age three. The study subjects were divided into five different groups, and each group of children returned only once to participate in the experiment, from the ages of five to nine.

While the children between the ages of five and seven could recall 63 to 72 percent of the events, the children who were eight and nine years old remembered only about 35 percent of the events.

"One surprising finding was that, although the five-and-six year-old children remembered a higher percentage of the events, their narratives of these events were less complete," Bauer says. "The older children remembered fewer events, but the ones they remembered had more detail."

Some reasons for this difference may be that memories that stick around longer may have richer detail associated with them and increasing language skills enable an older child to better elaborate the memory, further cementing it in their minds, Bauer says.

Young children tend to forget events more rapidly than adults do because they lack the strong neural processes required to bring together all the pieces of information that go into a complex autobiographical memory, she explains. "You have to learn to use a calendar and understand the days of the week and the seasons. You need to encode information about the physical location of the event. And you need development of a sense of self, an understanding that your perspective is different from that of someone else."

 

She uses an analogy of pasta draining in a colander to explain the difference between early childhood and adult memories.

"Memories are like orzo," she says, referring to the rice-grained-sized pasta, "little bits and pieces of neural encoding."

Young children's brains are like colanders with large holes trying to retain these little pieces of memory. "As the water rushes out, so do many of the grains of orzo," Bauer says. "Adults, however, use a fine net instead of a colander for a screen."

Now that Bauer has documented the onset of childhood amnesia, she hopes to hone in on the age that people acquire an adult memory system, which she believes is between the age of nine and the college years.

"We'd like to know more about when we trade in our colanders for a net," she says. "Between the ages of 9 and 18 is largely a no-man's land of our knowledge of how memory forms."

Source:Science Daily

N.H.Khidr

Toward fixing damaged hearts through tissue engineering

 Someone suffers a heart attack every 34 seconds -- their heart is starved of oxygen and suffers irreparable damage. Engineering new heart tissue in the laboratory that could eventually be implanted into patients could help, and scientists are reporting a promising approach tested with rat cells. They published their results on growing cardiac muscle using a scaffold containing carbon nanofibers in the ACS journal Biomacromolecules.

Gordana Vunjak-Novakovic, Rui L. Reis, Ana Martins and colleagues point out that when damaged, adult heart tissue can't heal itself very well. The only way to fix an injured heart is with a transplant. But within the past decade, interest in regenerating just the lost tissue has surged. The trick is to find materials that, among other things, are nontoxic, won't get attacked by the body's immune system and allow for muscle cells to pass the electrical signals necessary for the heart to beat. Previous research has found that chitosan, which is obtained from shrimp and other crustacean shells, nearly fits the bill. In lab tests, scientists have used it as a scaffold for growing heart cells. But it doesn't transmit electrical signals well. Vunjak-Novakovic's team decided to build on the chitosan development and coax it to function more like a real heart.

To the chitosan, they added carbon nanofibers, which can conduct electricity, and grew neonatal rat heart cells on the resulting scaffold. After two weeks, cells had filled all the pores and showed far better metabolic and electrical activity than with a chitosan scaffold alone. The cells on the chitosan/carbon scaffold also expressed cardiac genes at higher levels.

Source: sciencedaily.com

B.N

Discovery of 'Fat' Taste Could Hold the Key to Reducing Obesity

A newly discovered ability for people to taste fat could hold the key to reducing obesity, Deakin University health researchers believe.

Deakin researchers Dr Russell Keast and PhD student Jessica Stewart, working with colleagues at the University of Adelaide, CSIRO, and Massey University (New Zealand), have found that humans can detect a sixth taste -- fat. They also found that people with a high sensitivity to the taste of fat tended to eat less fatty foods and were less likely to be overweight. The results of their research are published in the latest issue of the British Journal of Nutrition.

"Our findings build on previous research in the United States that used animal models to discover fat taste," Dr Keast said.

"We know that the human tongue can detect five tastes -- sweet, salt, sour, bitter and umami (a taste for identifying protein rich foods). Through our study we can conclude that humans have a sixth taste -- fat."

The research team developed a screening procedure to test the ability of people to taste a range of fatty acids commonly found in foods.

They found that people have a taste threshold for fat and that these thresholds vary from person to person; some people have a high sensitivity to the taste while others do not.

"Interestingly, we also found that those with a high sensitivity to the taste of fat consumed less fatty foods and had lower BMIs than those with lower sensitivity," Dr Keast said.

"With fats being easily accessible and commonly consumed in diets today, this suggests that our taste system may become desensitised to the taste of fat over time, leaving some people more susceptible to overeating fatty foods.

"We are now interested in understanding why some people are sensitive and others are not, which we believe will lead to ways of helping people lower their fat intakes and aide development of new low fat foods and diets

Source: Science Daily

N.H.Khider

Aggression Strongly Associated With Genetic Factors

The development of physical aggression in toddlers is strongly associated with genetic factors and to a lesser degree with the environment, according to a new study led by Eric Lacourse of the University of Montreal and its affiliated CHU Sainte-Justine Hospital. Lacourse's worked with the parents of identical and non-identical twins to evaluate and compare their behavior, environment and genetics.

"The gene-environment analyses revealed that early genetic factors were pervasive in accounting for developmental trends, explaining most of the stability and change in physical aggression, " Lacourse said. "However, it should be emphasized that these genetic associations do not imply that the early trajectories of physical aggression are set and unchangeable. Genetic factors can always interact with other factors from the environment in the causal chain explaining any behavior."

Lacourse and his colleagues posited and tested three general patterns regarding the developmental roles of genetic and environmental factors in physical aggression. First, the most consensual and general point of view is that both sources of influence are ubiquitous and involved in the stability of physical aggression. Second, a "genetic set point" model suggests a single set of genetic factors could account for the level of physical aggression across time. A third pattern labeled 'genetic maturation' postulates new sources of genetic and environmental influences with age. "According to the genetic maturation hypothesis, new environmental contributions to physical aggression could be of short duration in contrast to genetic factors," Lacourse explained

Source: .sciencedaily.com

B.N

It's All Coming Back to Me Now: Researchers Find Caffeine Enhances Memory

For some, it's the tradition of steeping tealeaves to brew the perfect cup of tea. For others, it's the morning shuffle to a coffee maker for a hot jolt of java. Then there are those who like their wake up with the kind of snap and a fizz usually found in a carbonated beverage.

Regardless of the routine, the consumption of caffeine is the energy boost of choice for millions to wake up or stay up. Now, however, researchers at the Johns Hopkins University have found another use for the stimulant: memory enhancer.

Michael Yassa, assistant professor of psychological and brain sciences in the Krieger School of Arts and Sciences at Johns Hopkins, and his team of scientists found that caffeine has a positive effect on long-term memory in humans. Their research, published by the journal Nature Neuroscience, shows that caffeine enhances certain memories at least up to 24 hours after it is consumed.

The memory center in the human brain is the hippocampus, a seahorse-shaped area in the medial temporal lobe of the brain. The hippocampus is the switchbox for all short-term and long-term memories. Most research done on memory -- the effects of concussions in athletics to war-related head injuries to dementia in the aging population -- are focused on this area of the brain.

Until now, caffeine's effects on long-term memory had not been examined in detail. Of the few studies done, the general consensus was that caffeine has little or no effect on long-term memory retention.

" According to the U.S. Food and Drug Administration, 90 percent of people worldwide consume caffeine in one form or another. In the United States, 80 percent of adults consume caffeine every day. The average adult has an intake of about 200 milligrams -- the same amount used in the Yassa study -- or roughly one strong cup of coffee or two small cups of coffee per day.

 Source : Science Daily

N.H.Khider