Posts tagged primates
Articles and news from the latest research reports.
Even if there was no God, even if human beings had no soul, it would still be true that evolution had created a remarkable animal — the human animal — during its millions of years of labor. So very like our closest biological relatives, the chimpanzees, yet so different. For our study of the chimpanzees had helped to pinpoint not only the similarities between them and us, but also those ways in which we are most different. Admittedly, we are not the only beings with personalities, reasoning powers, altruism, and emotions like joy and sorrow; nor are we the only beings capable of mental as well as physical suffering. But our intellect has grown mighty in complexity since the first true men branched off from the ape-man stock some two million years ago. And we, and only we, have developed a sophisticated spoken language. For the first time in evolution, a species evolved that was able to teach its young about objects and events not present, to pass on wisdom gleaned from the successes — and the mistakes — of the past, to make plans for the distant future, to discuss ideas so that they could grow, sometimes out of all recognition, through the combined wisdom of the group.
Childhood’s end: ADHD, autism and schizophrenia tied to stronger inhibitory interactions in adolescent prefrontal cortex
Key cognitive functions such as working memory (which combines temporary storage and manipulation of information) and executive function (a set of mental processes that helps connect past experience with present action) are associated with the brain’s prefrontal cortex. Unlike other brain regions, the prefrontal cortex does not mature until early adulthood, with the most pronounced changes being seen between its peripubertal (onset of puberty) and postpubertal developmental states. Moreover, this maturation period is correlated with cognitive maturation – but the physical neuronal changes during this transition have remained for the most part unknown. Recently, however, scientists at the Wake Forest School of Medicine in Winston-Salem, NC recorded and compared prefrontal cortical activity peripubertal and adult monkeys.
The researchers found that compared with adults, peripubertal monkeys showed lower connectivity due to stronger inhibitory interactions, suggesting that intrinsic (or resting state) inhibitory connections – that is, inhibitory neural connections that are active in the absence of any particular task – decline with maturation. The scientists then concluded that prefrontal intrinsic connectivity changes are a possible substrate for cognitive maturation.
Prof. Christos Constantinidis discusses the paper that he, Dr. Xin Zhou and their co-authors published in Proceedings of the National Academy of Sciences. When comparing the functional connectivity between pairs of neurons in neuronal activity recorded from the prefrontal cortex of peripubertal and adult monkeys and evaluating the developmental stage of peripubertal rhesus monkeys with a series of morphometric, hormonal, and radiographic measures, Constantinidis tells Medical Xpress that a major challenge was to obtain neural activity from the brain of monkeys around the time of puberty. “We needed to make ourselves experts in the developmental trajectories of monkeys and conduct experiments just at the right time relative to the onset of puberty,” he explains.
What makes us human? Unique brain area linked to higher cognitive powers
Oxford University researchers have identified an area of the human brain that appears unlike anything in the brains of some of our closest relatives.
The brain area pinpointed is known to be intimately involved in some of the most advanced planning and decision-making processes that we think of as being especially human.
'We tend to think that being able to plan into the future, be flexible in our approach and learn from others are things that are particularly impressive about humans. We've identified an area of the brain that appears to be uniquely human and is likely to have something to do with these cognitive powers,' says senior researcher Professor Matthew Rushworth of Oxford University's Department of Experimental Psychology.
MRI imaging of 25 adult volunteers was used to identify key components in the ventrolateral frontal cortex area of the human brain, and how these components were connected up with other brain areas. The results were then compared to equivalent MRI data from 25 macaque monkeys.
Monkeys can point to objects they do not report seeing
Are monkeys, like humans, able to ascertain where objects are located without much more than a sideways glance? Quite likely, says Lau Andersen of the Aarhus University in Denmark, lead author of a study conducted at the Yerkes National Primate Research Center of Emory University, published in Springer’s journal Animal Cognition. The study finds that monkeys are able to localize stimuli they do not perceive.
Humans are able to locate, and even side-step, objects in their peripheral vision, sometimes before they perceive the object even being present. Andersen and colleagues therefore wanted to find out if visually guided action and visual perception also occurred independently in other primates.
The researchers trained five adult male rhesus monkeys (Macaca mulatta) to perform a short-latency, highly stereotyped localization task. Using a touchscreen computer, the animals learned to touch one of four locations where an object was briefly presented. The monkeys also learned to perform a detection task using identical stimuli, in which they had to report the presence or absence of an object by pressing one of two buttons. These techniques are similar to those used to test normal humans, and therefore make an especially direct comparison between humans and monkeys possible. A method called “visual masking” was used to systematically reduce how easily a visual target was processed.
Andersen and his colleagues found that the monkeys were still able to locate targets that they could not detect. The animals performed the tasks very accurately when the stimuli were unmasked, and their performance dropped when visual masking was employed. But monkeys could still locate targets at masking levels for which they reported that no target had been presented. While these results cannot establish the existence of phenomenal vision in monkeys, the discrepancy between visually guided action and detection parallels the dissociation of conscious and unconscious vision seen in humans.
“Knowing whether similar independent brain systems are present in humans and nonverbal species is critical to our understanding of comparative psychology and the evolution of brains,” explains Andersen.
(Source: springer.com)
Chimpanzees communicate with robots
Chimpanzees are willing to socialise with robots, new research reveals. It is the first time that robots have been used to study behaviour in primates other than humans.
The study, by researchers at the University of Portsmouth, shows that chimps respond to even basic movements made by a robot, demonstrating that chimps want to communicate and interact with other ‘creatures’ on a social level. The researchers believe that these basic forms of communication in chimpanzees help to promote greater social bonding and lead to more complex forms of social interaction.
The research, published in Animal Cognition a few days ago, outlines how chimps responded to a human-like robot about the size of a doll. The chimps reacted to small movements made by the robot by inviting play, offering it toys and in one case even laughing at it. They also responded to being imitated by the robot.
The chimps did not appear to be put off by the primitive nature of the gestures but responded in the same way they might to humans or other chimps.
Lead researcher, Dr Marina Davila-Ross, is from the University’s Centre for Comparative and Evolutionary Psychology. She said that the advantage of using a robot in the study was that the chimps could be observed in a controlled but interactive setting while a human researcher was able to examine the chimps’ behaviour without needing to participate. This allowed the researchers to analyse simplest forms of ’social’ interactions.
She said: “It was especially fascinating to see that the chimps recognised when they were being imitated by the robot because imitation helps to promote their social bonding. They showed less active interest when they saw the robot imitate a human.
“Some of the chimps gave the robot toys and other objects and demonstrated an active interest in communicating. This kind of behaviour helps to promote social interactions and friendships. But there were notable differences in how the chimps behaved. Some chimps, for instance, seemed not interested in interacting with the robot and turned away as soon as they saw it.
“In our other studies we have found that humans will also react to robots in ways which suggest a willingness to communicate, even though they know the robots are not real. It’s a demonstration of the basic human desire to communicate and it appears that chimpanzees share this readiness to communicate with others.”
The interactive robot was approximately 45 centimetres high and its head and limbs could move independently while chimpanzee sounds (such as chimpanzee laughter) were sent via a small loudspeaker in its chest area, which was covered by a dress. The chimps first observed a person interacting with the robot which was then turned around to face the chimp while the human researcher looked away to avoid any further communication.
Almost all of the 16 chimpanzees observed showed a level of active communication with the robot, such as gestures and expressions.
Dr Davila-Ross said that the research paves the way for further study using robots to interact with primates and discover more about their social behaviour in a controlled setting, such as how they make friends.
Primate brain development follows a predictable pattern
In a breakthrough for understanding brain evolution, neuroscientists have shown that differences between primate brains - from the tiny marmoset to human – can be largely explained as consequences of the same genetic program.
In research published in the Journal of Neuroscience, Professor Marcello Rosa and his team at Monash University’s School of Biomedical Sciences and colleagues at Universidade Federal do Rio de Janeiro, in Brazil, used computer modelling to demonstrate that the substantial enlargement of some areas of the human brain, vital to advanced cognition, reflected a consistent pattern that is seen across primate species of all sizes.
This finding suggests how the neural circuits responsible for traits that we consider uniquely human – such as the ability to plan, make complex decisions and speak – could have emerged simply as a natural consequence of the evolution of larger brains.
“We have known for a long time that certain areas of the human brain are much larger than one would expect based on how monkey brains are organised,” Professor Rosa said.
“What no one had realised is that this selective enlargement is part of a trend that has been present since the dawn of primates.”
Using publicly available brain maps, MRI imaging data and modelling software, the neuroscientists compared the sizes of different brain areasin humans and three monkey species: marmosets, capuchins and macaques. They found that two regions, the lateral prefrontal cortex and the temporal parietal junction, expand disproportionally to the rest of the brain.
The prefrontal cortex is related to long term planning, personality expression, decision-making, and behaviour modification. The temporal parietal junction is related to self-awareness and self-other distinction.
Lead author Tristan Chaplin, from the Department of Physiology will commence his PhD next year. He said the findings showed that those areas of the brain grew disproportionately in a predictable way.
“We found that the larger the brain is, the larger these areas get,” Tristan said.
“When you go from a small to big monkey - the marmoset to macaque - the prefrontal cortex and temporal parietal junction get larger relative to the rest of the cortex, and we see the same thing again when you compare macaques to humans.”
“This trend argues against the view that specific human mutations gave us these larger areas and advanced cognition and behaviour, but are a consequence of what happens in development when you grow a larger brain,” Tristan said.
Professor Rosa said the pattern held for primate species that evolved completely separately.
"If you compare the capuchin of South America and the macaque of Asia, their brains are almost identical, although they developed on opposite sides of the world. They both reflect the genetic plan of how a primate brain grows," Professor Rosa said.
This is the first computational comparative study conducted across several primate species. Tristan now hopes, in collaboration with zoos, to check if our closest primate relatives, the chimpanzees and gorillas, also have brain areas organised as his theory predicts.
(Source: monash.edu.au)
Shout now! ‒ How Nerve Cells Initiate Voluntary Calls
University of Tübingen neuroscientists show that monkeys can decide to call out or keep silent
“Should I say something or not?” Human beings are not alone in pondering this dilemma – animals also face decisions when they communicate by voice. University of Tübingen neurobiologists Dr. Steffen Hage and Professor Andreas Nieder have now demonstrated that nerve cells in the brain signal the targeted initiation of calls – forming the basis of voluntary vocal expression. Their results are published in “Nature Communications.”
When we speak, we use the sounds we make for a specific purpose – we intentionally say what we think, or consciously withhold information. Animals, however, usually make sounds according to what they feel at that moment. Even our closest relations among the primates make sounds as a reflex based on their mood. Now, Tübingen neuroscientists have shown that rhesus monkeys are able to call (or be silent) on command. They can instrumentalize the sounds they make in a targeted way, an important behavioral ability which we also use to put language to a purpose.
To find out how the neural cells in the brain catalyse the production of controled vocal noises, the researchers taught rhesus monkeys to call out quickly when a spot appeared on a computer screen. While the monkeys solved puzzles, measurements taken in their prefrontal cortex revealed astonishing reactions in the cells there. The nerve cells became active whenever the monkey saw the spot of light which was the instruction to call out. But if the monkey simply called out spontaneously, these nerve cells were not activated. The cells therefore did not signaled for just any vocalisation – only for calls that the monkey actively decided to make.
The results published in “Nature Communications” provide valuable insights into the neurobiological foundations of vocalization. “We want to understand the physiological mechanisms in the brain which lead to the voluntary production of calls,” says Dr. Steffen Hage of the Institute for Neurobiology, “because it played a key role in the evolution of human ability to use speech.” The study offers important indicators of the function of part of the brain which in humans has developed into one of the central locations for controlling speech. “Disorders in this part of the human brain lead to severe speech disorders or even complete loss of speech in the patient,” Professor Andreas Nieder explains. The results – giving insights into how the production of sound is initiated – may help us better understand speech disorders.
(Source: uni-tuebingen.de)
Primate calls, like human speech, can help infants form categories
Human infants’ responses to the vocalizations of non-human primates shed light on the developmental origin of a crucial link between human language and core cognitive capacities, a new study reports.
Previous studies have shown that even in infants too young to speak, listening to human speech supports core cognitive processes, including the formation of object categories.
Alissa Ferry, lead author and currently a postdoctoral fellow in the Language, Cognition and Development Lab at the Scuola Internationale Superiore di Studi Avanzati in Trieste, Italy, together with Northwestern University colleagues, documented that this link is initially broad enough to include the vocalizations of non-human primates.
"We found that for 3- and 4-month-old infants, non-human primate vocalizations promoted object categorization, mirroring exactly the effects of human speech, but that by six months, non-human primate vocalizations no longer had this effect — the link to cognition had been tuned specifically to human language," Ferry said.
In humans, language is the primary conduit for conveying our thoughts. The new findings document that for young infants, listening to the vocalizations of humans and non-human primates supports the fundamental cognitive process of categorization. From this broad beginning, the infant mind identifies which signals are part of their language and begins to systematically link these signals to meaning.
Furthermore, the researchers found that infants’ response to non-human primate vocalizations at three and four months was not just due to the sounds’ acoustic complexity, as infants who heard backward human speech segments failed to form object categories at any age.
Susan Hespos, co-author and associate professor of psychology at Northwestern said, “For me, the most stunning aspect of these findings is that an unfamiliar sound like a lemur call confers precisely the same effect as human language for 3- and 4-month-old infants. More broadly, this finding implies that the origins of the link between language and categorization cannot be derived from learning alone.”
"These results reveal that the link between language and object categories, evident as early as three months, derives from a broader template that initially encompasses vocalizations of human and non-human primates and is rapidly tuned specifically to human vocalizations," said Sandra Waxman, co-author and Louis W. Menk Professor of Psychology at Northwestern.
Waxman said these new results open the door to new research questions.
"Is this link sufficiently broad to include vocalizations beyond those of our closest genealogical cousins," asks Waxman, "or is it restricted to primates, whose vocalizations may be perceptually just close enough to our own to serve as early candidates for the platform on which human language is launched?"
(Image: Corbis)
The brain processes complex stimuli more cumulatively than we thought
A new study reveals that the representation of complex features in the brain may begin earlier—and play out in a more cumulative manner—than previously thought.
The finding represents a new view of how the brain creates internal representations of the visual world. “We are excited to see if this novel view will dominate the wider consensus” said senior author Dr. Miyashita, who is also Professor of Physiology at the University of Tokyo’s School of Medicine, “and also about the potential impact of our new computational principle on a wide range of views on human cognitive abilities.”
The brain recalls the patterns and objects we observe by developing distinct neuronal representations that go along with them (this is the same way it recalls memories). Scientists have long hypothesized that these neuronal representations emerge in a hierarchical process limited to the same cortical region in which the representations are first processed.
Because the brain perceives and recognizes the external world through these internal images, any new information about the process by which this takes place has the power to inform our understanding of related functions, including knowledge acquisition and memory.
However, studies attempting to uncover the functional hierarchy involved in the cortical process of visual stimuli have tried to characterize this hierarchy by analyzing the activity of single nerve cells, which are not necessarily correlated with neurons nearby, thus leaving these analyses lacking.
In a new study appearing in the 12 July issue of the journal Science, lead author Toshiyuki Hirabayashi and colleagues focus not on single neurons but instead on the relationship between neuron pairs, testing the possibility that the representation of an object in a single brain region emerges in a hierarchically lower brain area.
"I became interested in this work," said Dr. Hirabayashi, "because I was impressed by the elaborate neuronal circuitry in the early visual system, which is well-studied, and I wanted to explore the circuitry underlying higher-order visual processing, which is not yet fully understood."
Hirabayashi and colleagues analyzed nerve cell pairs in cortical areas TE and 36, the latter of which is hierarchically higher, in two adult macaques. After these animals looked at six sets of paired stimuli for several months to learn to associate related objects (a process that can lead to pair-coding neurons in the brain), the researchers recorded neuron responses in areas TE and 36 of both animals as they again performed this task.
The neurons exhibited pair association, but not where the researchers would have thought. “The most surprising result,” said senior author Dr. Yasushi Miyashita “was that the neuronal circuit that generated pair-association was found only in area TE, not in area 36.” Indeed, based on previous studies, which indicated that the number of pair-coding neurons in area TE is much smaller, the researchers would have expected the opposite.
During their study, Miyashita and other team members observed that in region TE of the macaque cortex, unit 1 neurons (or source neurons) provided input to unit 2 neurons (or target neurons), which—unlike unit 1 neurons—responded to both members of a stimulus pair.
"The representations generated in area TE did not reflect a mere random fluctuation of response patterns," explained Dr. Miyashita, "but rather, they emerged as a result of circuit processing inherent to that area of the brain."
In area 36, meanwhile, members of neuron pairs behaved differently; on average, unit 1 as well as unit 2 neurons responded to both members of a stimulus pair. Neurons in area 36 received input from area TE, but only from its unit 2 neurons.
Taken together, these findings lead the authors to hypothesize the existence of a hierarchical relationship between regions TE and 36, in which paired associations first established in the former region are propagated to the latter one. Here, area 36 represents the next level of a so-called feed forward hierarchy.
The work by Hirabayashi and colleagues suggests that the detailed representations of objects commonly observed in the brain are attained not by buildup of representations in a single area, but by emergence of these representations in a hierarchically prior area and their subsequent transfer to the brain region that follows. There, they become sufficiently prevalent for the brain to register. The work also reveals that the brain activity involved in recreating visual stimuli emerges in a hierarchically lower brain area than previously thought.
Moving forward, the Japanese research team has plans to expand upon this research, thus continuing to contribute to studies worldwide that aim to give scientists the best possible tools with which to obtain a dynamic picture of the brain. As a next step, the team hopes to further elucidate interactions between the various cortical microcircuits that operate in memory encoding. Dr. Miyashita has conjectured that these microcircuits are manipulated by a global brain network. Using the results of this latest study, he and colleagues are poised to further evaluate this assumption.
"It will also be important to weave the neuronal circuit mechanisms into a unified framework," said Dr. Hirabayashi," and to examine the effects of learning on these circuit organizations."
Equipped with their new view of cortical processing, the team also hopes to trace the causal chain of memory retrieval across different areas of the cortex. “I am excited by the recent development of genetic tools that will allow us to do this,” said Dr. Miyashita. A better understanding of object representations from one area of the brain to the next will shed even greater light on elusive aspects of this hierarchical organ.
(Source: eurekalert.org)
Researchers Create 15-Million-Year Model Of Great Ape History
Using the study of genetic variation in a large panel of humans, chimpanzees, gorillas and orangutans, researchers from the Universitat Pompeu Fabra in Barcelona, Spain, and Washington University in Seattle have created a model of great ape history over the past 15 million years.
This is the most comprehensive catalog of great ape genetic diversity. The catalog elucidates the evolution and population histories of great apes from Africa and Indonesia. The research team hopes the catalog will also help current and future conservation efforts that strive to preserve natural genetic diversity in populations.
An international group of more than 75 scientists and wildlife conservationists worked on the genetic analysis of 79 wild and captive-born great apes. The group of great apes represents all six great ape species: chimpanzee, bonobo, Sumatran orangutan, Bornean orangutan, eastern gorilla and western lowland gorilla; as well as seven subspecies. The study, published in Nature, also included nine human genomes.
“The research provided us the deepest survey to date of great ape genetic diversity with evolutionary insights into the divergence and emergence of great-ape species,” noted Evan Eichler, a UW professor of genome sciences and a Howard Hughes Medical Institute Investigator.
Due to the difficulty in obtaining genetic specimens from wild apes, genetic variation among great apes had been largely uncharted prior to this study. The research team credits the many conservationists in various countries, many of them in dangerous or isolated locations, with the success of the project.
Peter H. Sudmant, a UW graduate student in genome sciences, said, “Gathering this data is critical to understanding differences between great ape species, and separating aspects of the genetic code that distinguish humans from other primates.”
Factors that shaped primate evolution, including natural selection, population growth and collapse, geographic isolation and migration, climate and geological changes are likely to be revealed by the analysis of great ape genetic diversity.
Understanding more about great ape genetic diversity, according to Sudmant, also contributes to knowledge about disease susceptibility among various primate species. This knowledge is important to both conservation efforts and to human health. For example, the ebola virus is responsible for thousands of chimp and gorilla deaths in Africa. Also, the origin of the HIV in humans comes from simian immunodeficiency virus (SIV), which is found in non-human primates.
“Because the way we think, communicate and act is what makes us distinctively human,” Sudmant, who works in a lab that studies both primate evolutionary biology and neuropsychiatric diseases such as autism, schizophrenia, developmental delay, and cognitive and behavioral disorders, said, “we are specifically looking for the genetic differences between humans and other great apes that might confer these traits.”
The differences between species may direct scientists to portions of the human genome associated with cognition, speech or behavior. This could provide clues to which mutations might underlie neurological disease.
The research team published a companion paper in Genome Research, in which they found the first genetic evidence of a disorder in chimpanzees that resembles Smith-Magenis syndrome. Smith-Magenis is a disabling physical, mental and behavioral condition in humans. The veterinary records of Suzie-A, the chimpanzee exhibiting the disorder, match human symptoms of Smith-Magenis almost exactly. Suzie-A was overweight, rage-prone, had a curved-spine and died from kidney failure.
The discovery of Suzie-A’s syndrome came about while the scientists were exploring and comparing the accumulation of copy number variants during great ape evolution, which are differences between individuals, populations or species in the number of times specific segments of DNA appear. The genomes of humans and great apes have been restructured by the duplication and deletion of DNA segments, which are also behind many genetic diseases.
The new catalog of genetic diversity will help address the challenging plight of great ape species on the brink of extinction, in addition to offering a view of the origins of humans and their disorders. It will also provide an important tool to allow biologists to identify the origin of great apes poached for their body parts or hunted for bush meat. The study also explains why current zoo breeding programs that have tried to increase the genetic diversity of their captive great ape populations have resulted in populations that are genetically dissimilar to their wild counterparts.
“By avoiding inbreeding to produce a diverse population, zoos and conservation groups may be entirely eroding genetic signals specific to certain populations in specific geographic locations in the wild,” Sudmant said.
Donald, one of the captive-bred apes studied by the team, had a genetic makeup of two distinct chimpanzee subspecies which are located around 1,250 miles away from each other in the wild.
The variety of changes that occurred along each of the ape lineages, as they separated from each other through migration, geological change and climate events, are delineated in the study findings. Natural disturbances such as the formation of rivers and the partition of islands from the mainland have all served to isolate groups of apes. These isolated populations are exposed to a unique set of environmental pressures that result in population fluctuations and adaptations, depending on the circumstances.
The ancestors of some present day apes were present at the same time as early human-like species. The researchers found, however, the evolutionary history of the ancestral great ape populations had far more complexity than that of humans. Human history appears “almost boring,” according to Sudmant and Eicher, when compared to our closest relatives, the chimpanzees. For example, the last few million years of chimp evolution are full of population explosions followed by implosions. These rapid fluctuations in chimpanzee populations demonstrate remarkable plasticity. Scientists still don’t understand the reasons for the fluctuations in chimpanzee population size long before our own population explosion.
Sudmant’s interest in studying and preserving the great apes stems from the similarities of the great apes to humans.
“If you look at a chimpanzee or a gorilla, those guys will look right back at you,” he said. “They act just like us. We need to find ways to protect these precious species from extinction.”