Brain activity shows infants are hardwired to link images, sounds as they learn to speak

Child learning (stock image). An international team of researchers in the UK and in Japan examined the electrical activities of the brain in 11 month-olds at the initial stages of word learning.

Credit: © mitgirl / Fotolia

New research examining electrical brain activity in infants suggests that we are biologically predisposed to link images and sounds to create language.

In a paper published in the journal Cortex, an international team of researchers in the UK and in Japan, including those at the University of Warwick, examined the electrical activities of the brain in 11 month-olds at the initial stages of word learning.

They used novel words ('kipi' or 'moma') to refer to pictures of a spiky or a rounded shape. They found the infants very quickly began to match the word to the image.

One of the authors, Dr Sotaro Kita from the University of Warwick said: 

"The oscillatory activity of the infant brainincreased when the word they heard matched the shape they were shown, compared to when it did not. This suggests that the infant brain spontaneously engages in matching visual and auditory input."

An analysis of how different areas of the brain are communicating with each other also showed surprising results.

Dr Kita said: "Communication traffic between regions of the brain was light when the word matched the shape, but the traffic became heavy especially in the left hemisphere, where language is typically processed, when the word did not match the shape. The left-hemisphere had to work harder to associate visual and auditory input when they are not a natural match."

"The N400 response was higher for mismatching word-image pairs, which is a classic index of word meaning processing in the brain. This indicates that the infants were trying to work out the meaning of the novel words."

Dr Kita added that these findings reveal that sound symbolism allows 11-month-old infants to spontaneously bind the speech sound and the visual referent, and this spontaneous binding may provide infants an insight that spoken words refers to objects you can see in the world.

He said: "It is this cross-modal mapping between sound and image that plays a key role in the origin and development of language-learning."

Story Source: The above story is based on materials provided by University of Warwick. 
Note: Materials may be edited for content and length.

Newborn neurons in adult brain may help us adapt to environment

The discovery that the human brain continues to produce new neurons in adulthood challenged a major dogma in the field of neuroscience, but the role of these neurons in behavior and cognition is still not clear. In a review article published by Cell Press February 21st in Trends in Cognitive Sciences, Maya Opendak and Elizabeth Gould of Princeton University synthesize the vast literature on this topic, reviewing environmental factors that influence the birth of new neurons in the adult hippocampus, a region of the brain that plays an important role in memory and learning.

The authors discuss how the birth of such neurons may help animals and humans adapt to their current environment and circumstances in a complex and changing world. They advocate for testing these ideas using naturalistic designs, such as allowing laboratory rodents to live in more natural social burrow settings and observing how circumstances such as social status influence the rate at which new neurons are born.

"New neurons may serve as a means to fine-tune the hippocampus to the predicted environment," Opendak says. "In particular, seeking out rewarding experiences or avoiding stressful experiences may help each individual optimize his or her own brain. However, more naturalistic experimental conditions may be a necessary step toward understanding the adaptive significance of neurons born in the adult brain."

In recent years, it has become increasingly clear that environmental influences have a profound effect on the adult brain in a wide range of mammalian species. Stressful experiences, such as restraint, social defeat, exposure to predator odors, inescapable foot shock, and sleep deprivation, have been shown to decrease the number of new neurons in the hippocampus. By contrast, more rewarding experiences, such as physical exercise and mating, tend to increase the production of new neurons in the hippocampus.

The birth of new neurons in adulthood may have important behavioral and cognitive consequences. Stress-induced suppression of adult neurogenesis has been associated with impaired performance on hippocampus-dependent cognitive tasks, such as spatial navigation learning and object memory. Stressful experiences have also been shown to increase anxiety-like behaviors that are associated with the hippocampus. In contrast, rewarding experiences are associated with reduced anxiety-like behavior and improved performance on cognitive tasks involving the hippocampus.

Although scientists generally agree that our day-to-day actions change our brains even in adulthood, there is some disagreement on the adaptive significance of new neurons. For instance, the literature presents mixed findings on whether new neurons generated under a specific experimental condition are geared toward the recognition of that particular experience or if they provide a more naive pool of new neurons that enable environmental adaptation in the future.

Gould and her collaborators recently proposed that stress-induced decreases in new neuron formation might improve the chances of survival by increasing anxiety and inhibiting exploration, thereby prioritizing safety and avoidant behavior at the expense of performing optimally on cognitive tasks. On the other hand, reward-induced increases in new neuron number may reduce anxiety and facilitate exploration and learning, leading to greater reproductive success.

"Because the past is often the best predictor of the future, a stress-modeled brain may facilitate adaptive responses to life in a stressful environment, whereas a reward-modeled brain may do the same but for life in a low-stress, high-reward environment," says Gould, a professor of psychology and neuroscience at Princeton University.
However, when aversive experiences far outnumber rewarding ones in both quantity and intensity, the system may reach a breaking point and produce a maladaptive outcome. For example, repeated stress produces continued reduction in the birth of new neurons, and ultimately the emergence of heightened anxiety and depressive-like symptoms.

"Such a scenario could represent processes that are engaged under pathological conditions and may be somewhat akin to what humans experience when exposed to repeated traumatic stress," Opendak says.

Because many studies that investigate adult neurogenesis use controlled laboratory conditions, the relevance of the findings to real-world circumstances remains unclear. The use of a visible burrow system--a structure consisting of tubes, chambers, and an open field--has allowed researchers to recreate the conditions that allow for the production of dominance hierarchies that rats naturally form in the wild, replicating the stressors, rewards, and cognitive processes that accompany this social lifestyle.

"This more realistic setting has revealed individual differences in adult neurogenesis, with more new neurons produced in dominant versus subordinate male rats," Gould says. "Taking findings from laboratory animals to the next level by exploring complex social interactions in settings that maximize individual variability, a hallmark of the human experience, is likely to be especially illuminating."

The above story is based on materials provided by Cell Press. Note: Materials may be edited for content and length.

Scientists Discover 'Reset' Button For Brain's Biological Clock

There's a master "circadian clock" in your brain that maintains your rhythms of sleeping and waking -- and for the first time, scientists may have found a way to control it.

Researchers at Vanderbilt University have discovered a "reset" button for this biological clock, which could pave the way for more effective treatments for seasonal affective disorder (SAD), jet lag and some of the negative health effects of shift work.

The biological clock is located in the brain's suprachiasmatic nucleus (SCN) -- a tiny region within the hypothalamus, a section of the brain that controls hormone production. The SCN maintains a 24-hour cycle of rest and activity that helps us figure out when we should be eating and sleeping. The cycle is also linked to biological activities like hormone regulation, brain wave activity and cell regeneration. And while these rhythms are regulated in the brain, they're affected by external cues like light and temperature.

In their research, the Vanderbilt scientists found that they were able to artificially stimulate mice's brains with a specific technique to change when the mice naturally woke up and went to sleep, without needing to change the light. They did this by stimulating or suppressing neurons in the SCN, effectively "resetting" the biological clock.

Researchers Jeff Jones, left, Michael Tackenberg and Douglas McMahon. (Steve Green / Vanderbilt)

To complete the study, the team genetically engineered two strains of mice. (They chose the animal because mice have a biological clock that's nearly identical to the ones humans have, except that mice are nocturnal.) In one strain, the neurons in the mice's brains contained a light-sensitive protein that triggers neuron activity when exposed to light. In the second strain of mice, the neurons had a similar protein that suppressed neural activity when exposed to light. In other words, one of the strains of mice was wired to be nocturnal, while the other was wired to be diurnal, or awake in the day.

Then, the researchers stimulated neurons in the biological clocks of both strains of mice using a laser and an optical fiber, through a technique called optogenetics -- a method that allows researchers to stimulate or suppress neurons with just a beam of light. First, light-sensitive genes are inserted into the neurons in order to make those neurons "turn on" when stimulated with the laser. By assessing how the neurons responded to the light, the researchers were able to both measure and control the rate at which neurons fired in the SCN.

By altering the firing of neurons in the SCN, the researchers could actually "reset" the mice's circadian rhythms -- shifting their internal schedules for sleeping and waking.

Jeff Jones, a researcher who worked on the study, told The Huffington Post that the team was able to use optogenetics "to directly activate the SCN in the absence of light," resetting the clock without changing anything external about the mice's environment.

According to Michael Tackenberg, a doctoral student who also worked on the study, scientists have been able to measure how quickly neurons fire within the biological clock, but they've never been able to control and alter the neural activity that happens there. Now, the optogenetic technique has given them the ability to do that.

While this approach isn't yet ready for human use, the Vanderbilt team and other researchers are making progress towards the eventual creation of targeted pharmaceuticals that could turn on and off neurons that are implicated in circadian-related health problems.

"These kinds of advances let the field investigate the system for drug targets more effectively," Tackenberg said. "If it were to be implemented, the type of stimulation that we used would theoretically be plausible in patients."

The findings were published in the February 2 issue of the journal Nature Neuroscience.