Researchers uncover why there is a mapping between pitch and elevation

Have you ever wondered why most natural languages invariably use the same spatial attributes – high versus low – to describe auditory pitch? Or why, throughout the history of musical notation, high notes have been represented high on the staff? According to a team of neuroscientists from Bielefeld University, the Max Planck Institute for Biological Cybernetics in Tübingen and the Bernstein Center Tübingen, high pitched sounds feel ‘high’ because, in our daily lives, sounds coming from high elevations are indeed more likely to be higher in pitch. This study has just appeared in the science journal PNAS.

Dr. Cesare Parise and colleagues set out to investigate the origins of the mapping between sound frequency and spatial elevation by combining three separate lines of evidence. First of all, they recorded and analyzed a large sample of sounds from the natural environment and found that high frequency sounds are more likely to originate from high positions in space. Next, they analyzed the filtering of the human outer ear and found that, due to the convoluted shape of the outer ear – the pinna – sounds coming from high positions in space are filtered in such a way that more energy remains for higher pitched sounds. Finally, they asked humans in a behavioural experiment to localize sounds with different frequency and found that high frequency sounds were systematically perceived as coming from higher positions in space.

The results from these three lines of evidence were highly convergent, suggesting that all such diverse phenomena as the acoustics of the human ear, the universal use of spatial terms for describing pitch, or the reason why high notes are represented higher in musical notation ultimately reflect the adaptation of human hearing to the statistics of natural auditory scenes. ‘These results are especially fascinating, because they do not just explain the origin of the mapping between frequency and elevation,’ says Parise, ‘they also suggest that the very shape of the human ear might have evolved to mirror the acoustic properties of the natural environment. What is more, these findings are highly applicable and provide valuable guidelines for using pitch to develop more effective 3D audio technologies, such as sonification-based sensory substitution devices, sensory prostheses, and more immersive virtual auditory environments.’

The mapping between pitch and elevation has often been considered to be metaphorical, and cross-sensory correspondences have been theorized to be the basis for language development. The present findings demonstrate that, at least in the case of the mapping between pitch and elevation, such a metaphorical mapping is indeed embodied and based on the statistics of the environment, hence raising the intriguing hypothesis that language itself might have been influenced by a set of statistical mappings between naturally occurring sensory signals.

Besides the mapping between pitch and elevation, human perception, cognition, and action are laced with seemingly arbitrary correspondences, such as that yellow–reddish colors are associated with a warm temperature or that sour foods taste sharp. This study suggests that many of these seemingly arbitrary mappings might in fact reflect statistical regularities to be found in the natural environment.

Lipid levels during prenatal brain development impact autism

In a groundbreaking York University study, researchers have found that abnormal levels of lipid molecules in the brain can affect the interaction between two key neural pathways in early prenatal brain development, which can trigger autism. And, environmental causes such as exposure to chemicals in some cosmetics and common over-the-counter medication can affect the levels of these lipids, according to the researchers.

“We have found that the abnormal level of a lipid molecule called Prostaglandin E2 in the brain can affect the function of Wnt proteins. It is important because this can change the course of early embryonic development,” explains Professor Dorota Crawford in the Faculty of Health and a member of the York Autism Alliance Research Group.

This is the first time research shows evidence for cross-talk between PGE2 and Wnt signalling in neuronal stem cells, according to the peer reviewed study published at Cell Communication and Signaling.

Lead researcher and York U doctoral student Christine Wong adds, “Using real-time imaging microscopy, we determined that higher levels of PGE2 can change Wnt-dependent behaviour of neural stem cells by increasing cell migration or proliferation. As a result, this could affect how the brain is organized and wired.  Moreover, we found that an elevated level of PGE2 can increase expression of Wnt-regulated genes — Ctnnb1, Ptgs2, Ccnd1, and Mmp9. “Interestingly, all these genes have been previously implicated in various autism studies.”

Autism is considered to be the primary disorder of brain development with symptoms ranging from mild to severe and including repetitive behaviour, deficits in social interaction, and impaired language. It is four times more prevalent in boys than in girls and the incidence continues to rise. The US Center for Disease Control and Prevention (CDC) data from 2010 estimates that 1 in 68 children now has autism.

“The statistics are alarming. It’s 30 per cent higher than the previous estimate of 1 in 88 children, up from only two years earlier. Perhaps we can no longer attribute this rise in autism incidence to better diagnostic tools or awareness of autism,” notes Crawford. “It’s even more apparent from the recent literature that the environment might have a greater impact on vulnerable genes, particularly in pregnancy. Our study provides some molecular evidence that the environment likely disrupts certain events occurring in early brain development and contributes to autism.”

According to Crawford, genes don’t undergo significant changes in evolution, so even though genetic factors are the main cause, environmental factors such as insufficient dietary supplementations of fatty acids, exposures to infections, various chemicals or drugs can change gene expression and contribute to autism.

Memory Accuracy and Strength Can Be Manipulated During Sleep

The sense of smell might seem intuitive, almost something you take for granted. But researchers from NYU Langone Medical Center have found that memory of specific odors depends on the ability of the brain to learn, process and recall accurately and effectively during slow-wave sleep — a deep sleep characterized by slow brain waves.

The sense of smell is one of the first things to fail in neurodegenerative disorders, such as Alzheimer’s disease, Parkinson’s disease, and schizophrenia. Indeed, down the road, if more can be learned from better understanding of how the brain processes odors, researchers believe it could lead to novel therapies that target specific neurons in the brain, perhaps enhancing memory consolidation and memory accuracy.

Reporting in the Journal of Neuroscience online April 9, researchers in the lab of Donald A. Wilson, PhD, a professor in the departments of Child and Adolescent Psychiatry and Neuroscience and Physiology at NYU Langone, and a research scientist at the NYU-affiliated Nathan Kline Institute for Psychiatric Research, showed in experiments with rats that odor memory was strengthened when odors sensed the previous day were replayed during sleep. Memories deepened more when odor reinforcement occurred during sleep than when rats were awake.

When the memory of a specific odor learned when the rats were awake was replayed during slow-wave sleep, they achieved a stronger memory for that odor the next day, compared to rats that received no replay, or only received replay when they were awake.

However, when the research team exposed the rats to replay during sleep of an odor pattern that they had not previously learned, the rats had false memories to many different odors. When the research team pharmacologically prevented neurons from communicating to each other during slow-wave sleep, the accuracy of memory of the odor was also impaired.

The rats were initially trained to recognize odors through conditioning. Using electrodes in the olfactory bulb, a part of the brain responsible for perceiving smells, the researchers stimulated different smell perceptions, according to precise patterns of electrical stimulation. Then, by replaying the patterns electrically, they were able to test the effects of slow-wave sleep manipulation.

Replay of learned electrical odors during slow-wave sleep enhanced the memory for those odors. When the learned smells were replayed while the rats were awake, the strength of the memory decreased. Finally, when a false pattern that the rat never learned was incorporated, the rats could not discriminate the smell accurately from the learned odor.

“Our findings confirm the importance of brain activity during sleep for both memory strength and accuracy,” says Dr. Wilson, the study’s senior author. “What we think is happening is that during slow-wave sleep, neurons in the brain communicate with each other, and in doing so, strengthen their connections, permitting storage of specific information.”

Dr. Wilson says these findings are the first to demonstrate that memory accuracy, not just memory strength, is altered during short-wave sleep. In future research, Dr. Wilson and his team hope to examine how sleep disorders affect memory and perception.

Language Structure… You’re Born with It

Humans are unique in their ability to acquire language. But how? A new study published in the Proceeding of the National Academy of Sciences shows that we are in fact born with the basic fundamental knowledge of language, thus shedding light on the age-old linguistic “nature vs. nurture” debate.

THE STUDY

While languages differ from each other in many ways, certain aspects appear to be shared across languages. These aspects might stem from linguistic principles that are active in all human brains. A natural question then arises: are infants born with knowledge of how the human words might sound like? Are infants biased to consider certain sound sequences as more word-like than others? “The results of this new study suggest that, the sound patterns of human languages are the product of an inborn biological instinct, very much like birdsong,” said Prof. Iris Berent of Northeastern University in Boston, who co-authored the study with a research team from the International School of Advanced Studies in Italy, headed by Dr. Jacques Mehler. The study’s first author is Dr. David Gómez.

BLA, ShBA, LBA

Consider, for instance, the sound-combinations that occur at the beginning of words. While many languages have words that begin by bl (e.g., blando in Italian, blink in English, and blusa in Spanish), few languages have words that begin with lb. Russian is such a language (e.g., lbu, a word related to lob, “forehead”), but even in Russian such words are extremely rare and outnumbered by words starting with bl. Linguists have suggested that such patterns occur because human brains are biased to favor syllables such as bla over lba. In line with this possibility, past experimental research from Dr. Berent’s lab has shown that adult speakers display such preferences, even if their native language has no words resembling either bla or lba. But where does this knowledge stem from? Is it due to some universal linguistic principle, or to adults’ lifelong experience with listening and producing their native language?

THE EXPERIMENT

These questions motivated our team to look carefully at how young babies perceive different types of words. We used near-infrared spectroscopy, a silent and non-invasive technique that tells us how the oxygenation of the brain cortex (those very first centimeters of gray matter just below the scalp) changes in time, to look at the brain reactions of Italian newborn babies when listening to good and bad word candidates as described above (e.g., blif, lbif).

Working with Italian newborn infants and their families, we observed that newborns react differently to good and bad word candidates, similar to what adults do. Young infants have not learned any words yet, they do not even babble yet, and still they share with us a sense of how words should sound. This finding shows that we are born with the basic, foundational knowledge about the sound pattern of human languages.

It is hard to imagine how differently languages would sound if humans did not share such type of knowledge. We are fortunate that we do, and so our babies can come to the world with the certainty that they will readily recognize the sound patterns of words–no matter the language they will grow up with.

(Image caption: The images show an early developmental stage of normal (top row) and BRCA1-deficient brains (bottom row). The imaged embryos show abundant proliferation of cell growth (red, first column) in both normal and BRCA1-deficient brains at this stage. However brains lacking BRCA1 exhibit high levels of cellular suicide (green, second column). The third column shows an overlay of the other columns. Credit: Courtesy of the Salk Institute for Biological Studies)

Scientists reveal potential link between brain development and breast cancer gene

Scientists at the Salk Institute have uncovered details into a surprising—and crucial—link between brain development and a gene whose mutation is tied to breast and ovarian cancer. Aside from better understanding neurological damage associated in a small percentage of people susceptible to breast cancers, the new work also helps to better understand the evolution of the brain.

The research, published this month in PNAS, shows that the gene known as BRCA1 has a significant role in creating healthy brains in mice and may provide a hint as to why some women genetically prone to breast cancer experience brain seizures.

"Previously, people associated mutations or deletions of BRCA1 with breast and ovarian cancer," says Inder Verma, a professor in Salk’s Laboratory of Genetics and American Cancer Society Professor of Molecular Biology. "Our paper goes beyond this link to explain the protective mechanism of BRCA1 in the brain."

Through a three–lab collaboration at the Salk Institute, which began over a water cooler conversation between adjacent lab researchers 10 years ago, the work has culminated in dramatic findings. The team found that eliminating BRCA1 in neural stems cells had profound effects: large swaths of brain were simply missing; the cortex, which typically has six layers, only developed two very rudimentary layers; the cerebellum, which is normally made up of many folds and creases, was almost completely smooth; and the olfactory bulb, which processes odor information, was severely disorganized and poorly developed. Neurons were dying rapidly shortly after forming, while ones that did last were often defective. In mouse models, this resulted in interference in balance, motor skills, and other core functions.

How exactly was the absence of BRCA1 leading to such a neural catastrophe? In a previous paper, the team showed that without the protein coded by the BRCA1 gene, DNA is not packaged properly, becoming fragile and more likely to break during DNA replication. In this new paper, the researchers reveal more about that mechanism, showing that without the protective ability of BRCA1, breaks in the DNA strands go unfixed, prompting the molecule ATM kinase to activate a cellular “suicide” pathway involving a protein called p53. This pathway helps to halt the replication of damaged cells and is important in cancer research.

"BRCA1 acts by conferring stability to the DNA and preventing it from breaking," says Carlos G. Perez–Garcia, a Salk researcher in the Molecular Neurobiology Lab. "BRCA1 is important for all healthy cells."

When the researchers eliminated both BRCA1 and p53, they found the neurons grew at a normal rate, but still disorderly, with cells pointed in the wrong direction.

"In this scenario, we recover a lot of neurons but there’s still a lot of abnormalities, such as cells that are sideways and pointed the wrong direction," says Gerald Pao, who, along with Quan Zhu and Perez–Garcia, is a primary contributor to the paper and Salk researcher.

This observation led the team to propose that BRCA1 has an additional role in assisting neurons in orienting: the gene acts on the centromere of DNA—essentially an anchor for the chromosome arms essential in cell replication—to tell the new cell in which direction to grow, providing guidance in developing the brain’s organized layers.

"It is remarkable that BRCA1 has such a significant effect on the brain, especially size. This work leads us to a better understanding of how to protect neurons," says Verma, who is also the Irwin and Joan Jacobs Chair in Exemplary Life Science. Because BRCA1 seems to regulate the centromere, studying the gene will help scientists to understand how mammalian brains have evolved over time.

"Now we have an explanation for why some patients with breast cancer also experienced brain seizures," adds Pao. This knowledge could potentially help identify breast cancer–susceptible patients predisposed to seizures and provide appropriate treatments.

Faster eye responses in Chinese people not down to culture

New research from University of Liverpool scientists has cast doubt on the theory that neurological behaviour is a product of culture in people of Chinese origin.

Scientists tested three groups – students from mainland China, British people with Chinese parents and white British people – to see how quickly their eyes reacted to dots appearing in the periphery of their vision.

These rapid eye movements, known as saccades, were timed in all of the participants to see which of them were capable of making high numbers of express saccades – particularly fast responses which begin a tenth of a second after a target appears.

The findings, published in the journal PLoS One, revealed that similar numbers of the British Chinese and mainland Chinese participants made high numbers express saccades, with the white British participants made far fewer. Culturally the British Chinese participants were similar to their white British counterparts and different to the mainland Chinese students.

Therefore in terms of eye movement patterns, Chinese ethnicity was more of a factor than culture. This is contrary to several previous reports from other research groups which looked at behaviour in Asian and white participants and concluded that culture explained behavioural differences between groups.

Neurophysiologist, Dr Paul Knox, from the University’s Institute of Ageing and Chronic Disease, led the study. He said: “Examining saccades from different populations is revealing a lot about underlying brain mechanisms and how we think.

"Many scientists believe that the eye movement patterns you develop are due to where you live – the books you read and the influence of your family, peers and community – your culture."

"Our research has shown that this cannot be the case, at least for saccade behaviour. What this leaves is the way we’re made, perhaps our genetics. And this may have a bearing on the way the brains in different groups react to injuries and disease."

All of the participants completed questionnaires which evaluated their cultural values. They then wore a headset and looked at a plain white board on which lights appeared. The headset measured the time it took for participants’ eyes to react to the lights as they appeared in different places on the board.

Twenty-seven percent of Chinese participants responded with high proportions of express saccades, similar to 22% of the British Chinese, but many more than the 10% of white British participants.

Dr Knox concluded: “From a situation where 80% of our understanding of neuroscience was derived from tests on US psychology undergraduates, we’re now showing how the human brain is not just amazingly complex in general, but also highly variable across the human population.”

(Image credit)

Scientists identify part of brain linked to gambling addiction

New research reveals that brain damage affecting the insula – an area with a key role in emotions – disrupts errors of thinking linked to gambling addiction.

The research, led by Dr Luke Clark from the University of Cambridge, was published on April 7 2014 in the journal PNAS.

During gambling games, people often misperceive their chances of winning due to a number of errors of thinking called cognitive distortions. For example, ‘near-misses’ seem to encourage further play, even though they are no different from any other loss. In a random sequence like tossing a coin, a run of one event (heads) makes people think the other outcome (tails) is due next; this is known as the ‘gambler’s fallacy’.

There is increasing evidence that problem gamblers are particularly prone to these erroneous beliefs. In this study, the researchers examined the neurological basis of these beliefs in patients with injuries to different parts of the brain.

“While neuroimaging studies can tell us a great deal about the brain’s response to complex events, it’s only by studying patients with brain injury that we can see if a brain region is actually needed to perform a given task,” said Dr Clark.

For the study, the researchers gave patients with injuries to specific parts of the brain (the ventromedial prefrontal cortex, the amygdala, or the insula) two different gambling tasks: a slot machine game that delivered wins and ‘near-misses’ (like a cherry one position from the jackpot line), and a roulette game involving red or black predictions, to elicit the gambler’s fallacy. For the control groups, they also had patients with injuries to other parts of the brain as well as healthy participants undergo the gambling tasks.

All of the groups with the exception of the patients with insula damage reported a heightened motivation to play following near-misses in the slot machine game, and also fell prey to the gambler’s fallacy in the roulette game.

Clark added: “Based on these results, we believe that the insula could be hyperactive in problem gamblers, making them more susceptible to these errors of thinking. Future treatments for gambling addiction could seek to reduce this hyperactivity, either by drugs or by psychological techniques like mindfulness therapies.”

Gambling is a widespread activity: 73% of people in the UK report some gambling involvement in the past year* and around 50% play games other than the National Lottery. For a small proportion of players (around 1-5%), their gambling becomes excessive, resulting in features seen in addiction. Problem gambling is associated with both debt and family difficulties as well as other mental health problems like depression.

Feelings of Failure, Not Violent Content, Foster Aggression in Video Gamers

The disturbing imagery or violent storylines of videos games like World of Warcraft or Grand Theft Auto are often accused of fostering feelings of aggression in players. But a new study shows hostile behavior is linked to gamers’ experiences of failure and frustration during play—not to a game’s violent content.

The study is the first to look at the player’s psychological experience with video games instead of focusing solely on its content. Researchers found that failure to master a game and its controls led to frustration and aggression, regardless of whether the game was violent or not. The findings of the study were published online in the March edition of the Journal of Personality and Social Psychology.

“Any player who has thrown down a remote control after losing an electronic game can relate to the intense feelings or anger failure can cause,” explains lead author Andrew Przybylski, a researcher at the Oxford Internet Institute at Oxford University, who said such frustration is commonly known among gamers as “rage-quitting.”

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