Date: September 14, 2015
Summary: Humans are extremely choosy when it comes to mating, only settling down after a long screening process involving nervous flirtations, awkward dates, humiliating rejections and the occasional lucky strike. But evolution is an unforgiving force — isn’t this choosiness rather a costly waste of time and energy when we should just be ‘going forth and multiplying?’ What, if anything, is the evolutionary point of it all? A new study may have the answer.
Doing a cost/benefit analysis of love is a challenging business, with many potential confounds, and — in the case of humans — some ethical limitations on doing experiments. A new study publishing on September 14th in the Open Access journal PLOS Biology by Malika Ihle, Bart Kempenaers, and Wolfgang Forstmeier from the Max Planck Institute for Ornithology, Seewiesen, Germany, describes an elegant experiment designed to tease apart the consequences of mate choice.
The authors took advantage of the fact that the zebra finch shares many characteristics with humans, mating monogamously for life, and sharing the burden of parental care. Female finches choose mates in a way that is specific to the individual, and there is little consensus among females as to who the cutest male is.
Using a population of 160 birds, the authors set up a speed-dating session, leaving groups of 20 females to choose freely between 20 males. Once the birds had paired off, half of the couples were allowed to go off into a life of wedded bliss. For the other half, however, the authors intervened like overbearing Victorian parents, splitting up the happy pair, and forcibly pairing them with other broken-hearted individuals.
Bird couples, whether happy or somewhat disgruntled, were then left to breed in aviaries, and the authors assessed couples’ behavior and the number and paternity of dead embryos, dead chicks and surviving offspring.
Strikingly, the final number of surviving chicks was 37% higher for individuals in chosen pairs than those in non-chosen pairs. The nests of non-chosen pairs had almost three times as many unfertilized eggs as the chosen ones, a greater number of eggs were either buried or lost, and markedly more chicks died after hatching. Most deaths occurred within the chicks’ first 48 hours, a critical period for parental care during which non-chosen fathers were markedly less diligent in their nest-care duties.
Watching the couples’ courtship showed some noticeable differences — although non-chosen males paid the same amount of attention to their mates as the chosen ones did, the non-chosen females were far less receptive to their advances, and tended to copulate less often. An analysis of harmonious behavior revealed that non-chosen couples were generally significantly less lovey-dovey than the chosen ones. There was also a higher level of infidelity in birds from non-chosen pairs — interestingly the straying of male birds increased as time went by while females roamed less.
Overall the authors conclude that birds vary rather idiosyncratically in their tastes, and choose mates on the basis that they find them stimulating in some way that isn’t necessarily obvious to an outside observer. This stimulation “turns on” the females to increase the likelihood of successful copulation and encourages paternal commitment for the time needed to raise young; together these maximize the couple’s likelihood of perpetuating their genes through their thriving offspring.
Sounds familiar? This is presumably what the human dating game is about, the need perhaps exacerbated by the extended phase of dependence during which our children need parental support. Indeed, these authors’ results are consistent with some studies on the differences between love-based and arranged marriages in human society.
The above post is reprinted from materials provided by PLOS. Note: Materials may be edited for content and length.
- Malika Ihle, Bart Kempenaers, Wolfgang Forstmeier. Fitness Benefits of Mate Choice for Compatibility in a Socially Monogamous Species. PLOS Biology, 2015; 13 (9): e1002248 DOI: 10.1371/journal.pbio.1002248
Feb. 7, 2013 — Cognitive decline in old age is linked to decreasing production of new neurons. Scientists from the German Cancer Research Center have discovered in mice that significantly more neurons are generated in the brains of older animals if a signaling molecule called Dickkopf-1 is turned off. In tests for spatial orientation and memory, mice in advanced adult age whose Dickkopf gene had been silenced reached an equal mental performance as young animals.
The hippocampus — a structure of the brain whose shape resembles that of a seahorse — is also called the “gateway” to memory. This is where information is stored and retrieved. Its performance relies on new neurons being continually formed in the hippocampus over the entire lifetime. “However, in old age, production of new neurons dramatically decreases. This is considered to be among the causes of declining memory and learning ability,” Prof. Dr. Ana Martin-Villalba, a neuroscientist, explains.
Martin-Villalba, who heads a research department at the German Cancer Research Center (DKFZ), and her team are trying to find the molecular causes for this decrease in new neuron production (neurogenesis). Neural stem cells in the hippocampus are responsible for continuous supply of new neurons. Specific molecules in the immediate environment of these stem cells determine their fate: They may remain dormant, renew themselves, or differentiate into one of two types of specialized brain cells, astrocytes or neurons. One of these factors is the Wnt signaling molecule, which promotes the formation of young neurons. However, its molecular counterpart, called Dickkopf-1, can prevent this.
“We find considerably more Dickkopf-1 protein in the brains of older mice than in those of young animals. We therefore suspected this signaling molecule to be responsible for the fact that hardly any young neurons are generated any more in old age.” The scientists tested their assumption in mice whose Dickkopf-1 gene is permanently silenced. Professor Christof Niehrs had developed these animals at DKFZ. The term “Dickkopf” (from German “dick” = thick, “Kopf” = head) also goes back to Niehrs, who had found in 1998 that this signaling molecule regulates head development during embryogenesis.
Martin-Villalba’s team discovered that stem cells in the hippocampus of Dickkopf knockout mice renew themselves more often and generate significantly more young neurons. The difference was particularly obvious in two-year old mice: In the knockout mice of this age, the researchers counted 80 percent more young neurons than in control animals of the same age. Moreover, the newly formed cells in the adult Dickkopf-1 mutant mice matured into potent neurons with multiple branches. In contrast, neurons in control animals of the same age were found to be more rudimentary already.
Blocking Dickkopf improves spatial orientation and memory
Several years ago, Ana Martin-Villalba had shown that mice lose their spatial orientation when neurogenesis in the hippocampus is blocked. Now, is it possible that the young neurons in Dickkopf-deficient mice improve the animals’ cognitive performance? The DKFZ researchers used standardized tests to study how the mice orient themselves in a maze. While in the control animals, the younger ones (3 months) performed much better in orienting themselves than the older ones (18 months), the Dickkopf-1-deficient mice showed no age-related decline in spatial orientation capabilities. Older Dickkopf-1 mutant mice also outperformed normal animals in tests determining spatial memory.
“Our result proves that Dickkopf-1 promotes age-related decline of specific cognitive abilities,” says Ana Martin-Villalba. “Although we had expected silencing of Dickkopf-1 to improve spatial orientation and memory of adult mice, we were surprised and impressed that animals in advanced adult age actually reach the performance levels of young animals.”
These results give rise to the question whether the function of Dickkopf-1 may be turned off using drugs. Antibodies blocking the Dickkopf protein are already being tested in clinical trials for treating a completely different condition. “It is fascinating to speculate that such a substance may also slow down age-related cognitive decline. But this is still a dream of the future, since we have only just started first experiments in mice to explore this question.”
Note: Materials may be edited for content and length. For further information, please contact the source cited above.
- Désirée R.M. Seib, Nina S. Corsini, Kristina Ellwanger, Christian Plaas, Alvaro Mateos, Claudia Pitzer, Christof Niehrs, Tansu Celikel, Ana Martin-Villalba. Loss of Dickkopf-1 Restores Neurogenesis in Old Age and Counteracts Cognitive Decline. Cell Stem Cell, 2013; 12 (2): 204 DOI: 10.1016/j.stem.2012.11.010
Feb. 7, 2013 — When migrating, sockeye salmon typically swim up to 4,000 miles into the ocean and then, years later, navigate back to the upstream reaches of the rivers in which they were born to spawn their young. Scientists, the fishing community and lay people have long wondered how salmon find their way to their home rivers over such epic distances.
How do they do that?
A new study, published in this week’s issue of Current Biology and partly funded by the National Science Foundation, suggests that salmon find their home rivers by sensing the rivers’ unique magnetic signature.
As part of the study, the research team used data from more than 56 years of catches in salmon fisheries to identify the routes that salmon had taken from their most northerly destinations, which were probably near Alaska or the Aleutian Islands in the Pacific Ocean, to the mouth of their home river–the Fraser River in British Columbia, Canada. This data was compared to the intensity of Earth’s magnetic field at pivotal locations in the salmon’s migratory route.
Earth has a magnetic field that weakens with proximity to the equator and distance from the poles and gradually changes on a yearly basis. Therefore, the intensity of the magnetosphere in any particular location is unique and differs slightly from year to year.
Because Vancouver Island is located directly in front of the Fraser River’s mouth, it blocks direct access to the river’s mouth from the Pacific Ocean. However, salmon may slip behind Vancouver Island and reach the river’s mouth from the north via the Queen Charlotte Strait or from the south via the Juan De Fuca Strait.
Results from this study showed that the intensity of the magnetic field largely predicted which route the salmon used to detour around Vancouver Island; in any given year, the salmon were more likely to take whichever route had a magnetic signature that most closely matched that of the Fraser River years before, when the salmon initially swam from the river into the Pacific Ocean.
“These results are consistent with the idea that juvenile salmon imprint on (i.e. learn and remember) the magnetic signature of their home river, and then seek that same magnetic signature during their spawning migration,” said Nathan Putman, a post-doctoral researcher at Oregon State University and the lead author of the study.
It has long been known that some animals use Earth’s magnetic field to generally orient themselves and to follow a straight course. However, scientists have never before documented an animal’s ability to “learn” the magnetic field rather than to simply inherit information about it or to use the magnetic field to find a specific location.
This study provides the first empirical evidence of magnetic imprinting in animals and represents the discovery of a major new phenomenon in behavioral biology.
In addition, this study suggests that it would be possible to forecast salmon movements using geomagnetic models–a development that has important implications for fisheries management.
Get out the map
Putman says scientists don’t know exactly how early and how often salmon check Earth’s magnetic field in order to identify their geographic locations during their trip back home. “But,” he says, “for the salmon to be able to go from some location out in the middle of the Pacific 4,000 miles away, they need to make a correct migratory choice early–and they need to know which direction to start going in. For that, they would presumably use the magnetic field.”
Putman continues, “As the salmon travel that route, ocean currents and other forces might blow them off course. So they would probably need to check their magnetic position several times during this migration to stay on track. Once they get close to the coastline, they would need to hone in on their target, and so would presumably check in more continuously during this stage of their migration.”
Putman says that once the salmon reach their home river, they probably use their sense of smell to find the particular tributary in which they were born. However, over long distances, magnetism would be a more useful cue to salmon than odors because magnetism–unlike odors–can be detected across thousands of miles of open ocean.
A long, strange trip
Like other Pacific Salmon, sockeye salmon spawn in the gravel beds of rivers and streams. After the newly hatched salmon emerge from these beds, they spend one to three years in fresh water, and then they migrate downstream to the ocean.
Next, the salmon travel thousands of miles from their home river to forage in the North Pacific for about two more years, and then, as well-fed adults, they migrate back to the same gravel beds in which they were born.
When migrating, salmon must transition from fresh water to sea water, and then back again. During each transition, the salmon undergo a metamorphosis that Putman says is almost as dramatic as the metamorphosis of a caterpillar into a butterfly. Each such salmon metamorphosis involves a replacement of gill tissues that enables the fish to maintain the correct salt balance in its environment: the salmon retains salt when in fresh water and pumps out excess salt when in salt water.
Salmon usually undertake their taxing, round-trip migration, which may total up to 8,000 miles, only once in their lives; they typically die soon after spawning.
Note: Materials may be edited for content and length. For further information, please contact the source cited above.
- Nathan F. Putman, Kenneth J. Lohmann, Emily M. Putman, Thomas P. Quinn, A. Peter Klimley, David L.G. Noakes.Evidence for Geomagnetic Imprinting as a Homing Mechanism in Pacific Salmon. Current Biology, 2013; DOI: 10.1016/j.cub.2012.12.041
Feb. 6, 2013 — Among the animals that are appealing “cover models” for scientific journals, lancelets don’t spring readily to mind. Slender, limbless, primitive blobs that look pretty much the same end to end, lancelets “are extremely boring. I wouldn’t recommend them for a home aquarium,” says Enrico Nasi, adjunct senior scientist in the MBL’s Cellular Dynamics Program. Yet Nasi and his collaborators managed to land a lancelet on the cover of The Journal of Neuroscience last December. These simple chordates, they discovered, offer insight into our own biological clocks.
The head of the marine invertebrate amphioxus (Branchiostoma floridae), magnified 15 times. Amphioxus are the most ancient of the chordates (animals whose features include a nerve cord), according to molecular analysis. They are important to the study of the origin of vertebrates. (Credit: Photo by Maria del Pilar Gomez)
Nasi and his wife, MBL adjunct scientist Maria del Pilar Gomez, are interested in photo-transduction, the conversion of light by light-sensitive cells into electrical signals that are sent to the brain. The lancelet, also called amphioxus, doesn’t have eyes or a true brain. But what it does have in surprising abundance is melanopsin, a photopigment that is also produced by the third class of light-sensitive cells in the mammalian retina, besides the rods and cones. This third class of cells, called “intrinsically photosensitive retinal ganglion cells” (ipRGCs), were discovered in 2002 by Brown University’s David Berson and colleagues. Now sometimes called “circadian receptors,” they are involved in non-visual, light-dependent functions, such as adjustment of the animal’s circadian rhythms.
“It seemed like colossal overkill that amphioxus have melanopsin-producing cells,” Nasi says. “These animals do nothing. If you switch on a light, they dance and float to the top of the tank, and then they drop back down to the bottom. That’s it for the day.” But that mystery aside, Gomez and Nasi realized that studying amphioxus could help reveal the evolutionary history of the circadian receptors.
As so it has. In 2009, Gomez and Nasi isolated the animal’s melanopsin-producing cells and described how they transduce light. In their recent paper, they tackled the puzzling question of why the light response of these amphioxus cells is several orders of magnitude higher than that of their more sophisticated, presumed descendents, the ipRGCs. (In mammals, the ipRGCs relay information on light and dark to the biological clock in the hypothalamus, where it is crucial for the regulation of circadian rhythms and associated control of hormonal secretion.)
By detailing how the large light response occurs in the amphioxus cells, Gomez and Nasi could relate their observations to the functional changes that may have occurred as the circadian receptors evolved and “eventually tailored their performance to the requirements of a reporter of day and night, rather than to a light sensor meant to mediate spatial vision.” The light-sensing cells of amphioxus, they discovered, may be the “missing link” between the visual cells of invertebrates and the circadian receptors in our own eyes.
Note: Materials may be edited for content and length. For further information, please contact the source cited above.
- C. Ferrer, G. Malagon, M. d. P. Gomez, E. Nasi.Dissecting the Determinants of Light Sensitivity in Amphioxus Microvillar Photoreceptors: Possible Evolutionary Implications for Melanopsin Signaling.Journal of Neuroscience, 2012; 32 (50): 17977 DOI:10.1523/JNEUROSCI.3069-12.2012
- M. del Pilar Gomez, J. M. Angueyra, E. Nasi. Light-transduction in melanopsin-expressing photoreceptors of Amphioxus. Proceedings of the National Academy of Sciences, 2009; 106 (22): 9081 DOI:10.1073/pnas.0900708106
Feb. 4, 2013 — Like a self-absorbed teenager, insects spend a lot of time grooming. In a study that delves into the mechanisms behind this common function, North Carolina State University researchers show that insect grooming — specifically, antennal cleaning — removes both environmental pollutants and chemicals produced by the insects themselves.
The findings, published online this week in Proceedings of the National Academy of Sciences, show that grooming helps insects maintain acute olfactory senses that are responsible for a host of functions, including finding food, sensing danger and even locating a suitable mate.
The findings could also explain why certain types of insecticides work more effectively than others.
Insects groom themselves incessantly, so NC State entomologist Coby Schal and post-doctoral researchers Katalin Boroczky and Ayako Wada-Katsumata wanted to explore the functions of this behavior.
They devised a simple set of experiments to figure out what sort of material insects were cleaning off their antennae, where this material was coming from, and the differences between how groomed and ungroomed antennae functioned. Schal likened the straightforwardness of some of the experiments to something you’d see in a well-equipped high-school science lab.
The researchers compared cleaned antennae of American cockroaches with antennae that were experimentally prevented from being cleaned. They found that grooming cleaned microscopic pores on the antennae that serve as conduits through which chemicals travel to reach sensory receptors for olfaction. Cockroaches clean their antennae by using forelegs to place the antennae in their mouths; they then methodically clean every segment of the antenna from base to tip.
The researchers found that both volatile and non-volatile chemicals accumulated on the ungroomed antennae of cockroaches, but most surprising was the accumulation of a great deal of cuticular hydrocarbons — fatty, candlewax-like substances secreted by the roaches to protect them against water loss.
“It is intuitive that insects remove foreign substances from their antennae, but it’s not necessarily intuitive that they groom to remove their ‘own’ substances,” Schal says.
The researchers also tested groomed and ungroomed cockroach antennae to gauge how well roaches picked up the scent of a known sex pheromone compound, as well as other odorants. Clean antennae responded to these signals much more readily than ungroomed antennae.
The researchers then put carpenter ants, houseflies and German cockroaches to many of the same tests. Although they groom a bit differently than cockroaches — flies and ants seem to rub their legs over their antennae to remove particulates, with ants then ingesting the material off their legs — the tests showed that these insects also accumulated more cuticular hydrocarbons when antennae went ungroomed.
“The evidence is strong: Grooming is necessary to keep these foreign and native substances at a particular level,” Schal says. “Leaving antennae dirty essentially blinds insects to their environment.”
Schal adds that there could be pest-control implications to the findings. An insecticide mist or dust that settles on a cockroach’s antennae, for instance, should be ingested by the roach rather quickly due to constant grooming. That method of insecticide delivery could be more effective than relying on residual insecticides to penetrate the thick cuticle, for instance.
Finally, Schal says the study can also be used as a caution to other researchers who use insects in experiments. Gluing shut an insect’s mouth to prevent it from feeding, for example, also prevents the insect from grooming its antennae. Experimental results could be skewed as a result of this sensory deprivation, Schal suggests.
Dale Batchelor, a researcher in NC State’s Analytical Instrumentation Facility, co-authored the paper, as did Marianna Zhukovskaya at the Russian Academy of Sciences. The research was supported by the National Institute of Food and Agriculture, the U.S. Department of Agriculture, the National Science Foundation and the Blanton J. Whitmire Endowment at NC State.
- Katalin Böröczky, Ayako Wada-Katsumata, Dale Batchelor, Marianna Zhukovskaya, and Coby Schal.Insects groom their antennae to enhance olfactory acuity. PNAS, February 4, 2013 DOI:10.1073/pnas.1212466110
Jan. 31, 2013 — For the first time, researchers have been able to see a thought “swim” through the brain of a living fish. The new technology is a useful tool for studies of perception. It might even find use in psychiatric drug discovery, according to authors of the study, appearing online on January 31 in Current Biology.
“Our work is the first to show brain activities in real time in an intact animal during that animal’s natural behavior,” said Koichi Kawakami of Japan’s National Institute of Genetics. “We can make the invisible visible; that’s what is most important.”
The technical breakthrough included the development of a very sensitive fluorescent probe to detect neuronal activity. Kawakami, along with Junichi Nakai of Saitama University and their colleagues, also devised a genetic method for inserting that probe right into the neurons of interest. The two-part approach allowed the researchers to detect neuronal activity at single-cell resolution in the zebrafish brain.
Akira Muto, the study’s lead author from the Kawakami lab, used the new tool to map what happens when a zebrafish sees something good to eat, in this case a swimming paramecium. The researchers were also able to correlate brain activity with that prey’s capture.
The new tool now makes it possible to ask which brain circuits are involved in complex behaviors, from perception to movement to decision making, the researchers say, noting that the basic design and function of a zebrafish brain is very much like our own.
“In the future, we can interpret an animal’s behavior, including learning and memory, fear, joy, or anger, based on the activity of particular combinations of neurons,” Kawakami said.
By monitoring neuronal activity in the zebrafish brain, Kawakami thinks that researchers may also be able to screen chemicals that affect neuronal activity in the brain. “This has the potential to shorten the long processes for the development of new psychiatric medications,” he said.
- Akira Muto, Masamichi Ohkura, Gembu Abe, Junichi Nakai, Koichi Kawakami. Real-Time Visualization of Neuronal Activity during Perception. Current Biology, 2013; DOI: 10.1016/j.cub.2012.12.040
Jan. 30, 2013 — The most sensitive patch of mammalian skin known to us isn’t human but on the star-shaped tip of the star-nosed mole’s snout. Researchers studying this organ have found that the star has a higher proportion of touch-sensitive nerve endings than pain receptors, according to a study published Jan. 30 in the open access journalPLOS ONE by Diana Bautista and colleagues from the University of California, Berkeley and Vanderbilt University.
Touch and pain are closely intertwined sensations, but very little is known about how these sensations are detected in our cells. In this study, the authors turned to a unique species for answers: the star-nosed mole. In addition to its distinction as the fastest-eating mammal known, the star-nosed mole also possesses one of the most sensitive tactile organs known in the animal kingdom. The star on its nose has the highest density of nerve endings known in any mammalian skin, with over 100,000 fibers in a patch of skin about 1 cm. in diameter. The authors found these nerve endings significantly enriched in neurons sensitive to light touch, with a lower proportion of neurons that detect and respond to pain.
The novel touch and pain receptors they identified in the star-nosed mole were also detected in sensory receptors in mice and humans, suggesting that these receptors are likely to be more common across other mammals as well. According to the authors, their results highlight how examining diverse and highly specialized species can reveal fundamental aspects of biology common across different animals.
Lead author on the study Bautista says, “By studying the star-nosed mole we identified candidate genes that may mediate touch and pain. These genes represent new potential targets for the development of much needed drugs and therapies to treat chronic pain.”
The authors are supported by a U.S. National Institutes of Health Innovator Award DOD007123A, the Pew Scholars Program, and the McKnight Scholars Fund (to DMB) and NSF grant 0844743 (to KCC).
The above story is reprinted from materials provided byPublic Library of Science.
- Kristin A. Gerhold, Maurizio Pellegrino, Makoto Tsunozaki, Takeshi Morita, Duncan B. Leitch, Pamela R. Tsuruda, Rachel B. Brem, Kenneth C. Catania, Diana M. Bautista.The Star-Nosed Mole Reveals Clues to the Molecular Basis of Mammalian Touch. PLoS ONE, 2013; 8 (1): e55001 DOI: 10.1371/journal.pone.0055001
Jan. 29, 2013 — While the wooly musk ox may like it cold, fruit flies definitely do not. They like it hot, or at least warm. In fact, their preferred optimum temperature is very similar to that of humans — 76 degrees F.
Scientists have known that a type of brain cell circuit helps regulate a variety of innate and learned behavior in animals, including their temperature preferences. What has been a mystery is whether or not this behavior stems from a specific set of neurons (brain cells) or overlapping sets.
Now, a new study from The Scripps Research Institute (TSRI) shows that a complex set of overlapping neuronal circuits work in concert to drive temperature preferences in the fruit fly Drosophila by affecting a single target, a heavy bundle of neurons within the fly brain known as the mushroom body. These nerve bundles, which get their name from their bulbous shape, play critical roles in learning and memory.
The study, published in the January 30, 2013 edition of the Journal of Neuroscience, shows that dopaminergic circuits — brain cells that synthesize dopamine, a common neurotransmitter — within the mushroom body do not encode a single signal, but rather perform a more complex computation of environmental conditions.
“We found that dopamine neurons process multiple inputs to generate multiple outputs — the same set of nerves process sensory information and reward-avoidance learning,” said TSRI Assistant Professor Seth Tomchik. “This discovery helps lay the groundwork to better understand how information is processed in the brain. A similar set of neurons is involved in behavior preferences in humans — from basic rewards to more complex learning and memory.”
Using imaging techniques that allow scientists to visualize neuron activity in real time, the study illuminated the response of dopaminergic neurons to changes in temperature. The behavioral roles were then examined by silencing various subsets of these neurons. Flies were tested using a temperature gradient plate; the flies moved from one place to another to express their temperature preferences.
As it turns out, genetic silencing of dopaminergic neurons innervating the mushroom body substantially reduces cold avoidance behavior. “If you give the fly a choice, it will pick San Diego weather every time,” Tomchik said, “but if you shut down those nerves, they suddenly don’t mind being in Minnesota.”
The study also showed dopaminergic neurons respond to cooling with sudden a burst of activity at the onset of a drop in temperature, before settling down to a lower steady-state level. This initial burst of dopamine could function to increase neuronal plasticity — the ability to adapt — during periods of environmental change when the organism needs to acquire new associative memories or update previous associations with temperature changes.
The study, “Dopaminergic Neurons Encode a Distributed, Asymmetric Representation of Temperature in Drosophila,” was supported by the National Institute of Mental Health of the National Institutes of Health (grant number K99 MH092294).
Jan. 28, 2013 — Japanese researchers show for the first time that primates modify their body movements to be in tune with others, just like humans do. Humans unconsciously modify their movements to be in synchrony with their peers. For example, we adapt our pace to walk in step or clap in unison at the end of a concert. This phenomenon is thought to reflect bonding and facilitate human interaction. Researchers from the RIKEN Brain Science Institute report that pairs of macaque monkeys also spontaneously coordinate their movements to reach synchrony.
This research opens the door to much-needed neurophysiological studies of spontaneous synchronization in monkeys, which could shed light into human behavioral dysfunctions such as those observed in patients with autism spectrum disorders, echopraxia and echolalia — where patients uncontrollably imitate others.
In the research, recently published in the journal Scientific Reports, the team led by Naotaka Fujii developed an experimental set-up to test whether pairs of Japanese macaque monkeys synchronize a simple push-button movement.
Before the experiment, the monkeys were trained to push a button with one hand. In a first experiment the monkeys were paired and placed facing each other and the timing of their push-button movements was recorded. The same experiment was repeated but this time each monkey was shown videos of another monkey pushing a button at varying speeds. And in a last experiment the macaques were not allowed to either see or hear their video-partner.
The results show that the monkeys modified their movements — increased or decreased the speed of their push-button movement — to be in synchrony with their partner, both when the partner was real and on video. The speed of the button pressing movement changed to be in harmonic or sub-harmonic synchrony with the partners’ speed. However, different pairs of monkeys synchronized differently and reached different speeds, and the monkeys synchronized their movements the most when they could both see and hear their partner.
The researchers note that this behavior cannot have been learnt by the monkeys during the experiment, as previous research has shown that it is extremely difficult for monkeys to learn intentional synchronization.
They add: “The reasons why the monkeys showed behavioral synchronization are not clear. It may be a vital aspect of other socially adaptive behavior, important for survival in the wild.”
The study was partly supported by Grant-in-Aid for Scientific Research on Innovative Areas ‘Neural creativity for communication’ (22120522 and 24120720) of MEXT, Japan.
- Yasuo Nagasaka, Zenas C. Chao, Naomi Hasegawa, Tomonori Notoya, Naotaka Fujii. Spontaneous synchronization of arm motion between Japanese macaques. Scientific Reports, 2013; 3 DOI:10.1038/srep01151