Older news items (pre-2010) brought over from the old website
Humans aren’t the only ones to think about what they know
As we get smarter about designing experiments and working out how to ask the right questions, the gap between human and non-human cognition keeps closing. Now a rat study has found evidence that rats can think about whether they know something or not. The study involved offering rats rewards for classifying a brief tone as either short or long. A right answer led to a large food reward; a wrong one, nothing. But on some tests runs, before starting, the rats were given a chance to back out of the test, in which case they got a small reward anyway. In some of the tests, the signal lengths were very different, making the discrimination very easy. But in others the difference was a lot harder to discern. In such a case, if the rats realized they couldn’t be sure of the answer, they would be better to forego the test and get the small, but guaranteed prize. Which was what was found.
[387] Foote, A. L., & Crystal J. D.
(2007). Metacognition in the Rat.
Current Biology. 17(6), 551 - 555.
http://www.world-science.net/othernews/070308_rats.htm
http://www.eurekalert.org/pub_releases/2007-03/cp-mfw030607.php
Size of brain areas does matter -- but bigger isn't necessarily better
In a fascinating mouse study that overturns our simplistic notion that, when it comes to the brain, bigger is better, researchers have found that there is an optimal size for regions within the brain. The study found that if areas of the cortex involved in body sensations and motor control are either smaller or larger than normal, mice couldn’t run an obstacle course, keep from falling off a rotating rod, or perform other tactile and motor behaviors that require balance and coordination as well as mice with normal-sized areas could. It now seems that the best size in one that is best tuned to the context of the neural system within which that area functions — which is not really so surprising when you consider that every brain region acts as part of a network, in conjunction with other regions. This study builds upon a previous discovery by the same researchers, that a gene controls how the cortex in mice is divided during embryonic development into its functionally specialized areas. Different levels of the protein expressed by this gene changes the size of the sensorimotor areas of the cortex. It is known that significant variability in cortical area size exists in humans, and this may explain at least in part variability in human performance.
[334] Leingärtner, A., Thuret S., Kroll T. T., Chou S-J., Leasure L. J., Gage F. H., et al.
(2007). Cortical area size dictates performance at modality-specific behaviors.
Proceedings of the National Academy of Sciences. 104(10), 4153 - 4158.
Full text is available at http://tinyurl.com/2tpyhe
http://www.physorg.com/news92051236.html
Neurons targeted by dementing illness may have evolved for complex social cognition
Special elongated nerve cells called spindle neurons, also known as Von Economo neurons (VENs), are found in two parts of the cerebral cortex known to be associated with social behavior, consciousness, and emotion (the anterior cingulate and fronto-insular cortex). They have only been found in humans and great apes, and, recently, whales. Because of this link with social behavior, and because these brain regions are targeted by frontotemporal dementia, a recent study investigated whether VENs play a role in this type of dementia that causes people to lose inhibition in social situations. Autopsies revealed that among FTD sufferers, the anterior cingulate cortex had a dramatic reduction in the number of VENs compared to controls. In contrast, Alzheimer's patients had only a small and statistically insignificant reduction.
[668] Seeley, W. W., Carlin D. A., Allman J. M., Macedo M. N., Bush C., Miller B. L., et al.
(2006). Early frontotemporal dementia targets neurons unique to apes and humans.
Annals of Neurology. 60(6), 660 - 667.
http://sciencenow.sciencemag.org/cgi/content/full/2006/1222/1?etoc
http://www.sciencedaily.com/releases/2006/12/061222090935.htm
http://www.eurekalert.org/pub_releases/2006-12/uoc--wih122106.php
A cognitive strategy shared by human infants and our great-ape kin
There are two basic strategies for remembering the location of something: either remembering the features of the item (it was a tree, a stone, etc.), or knowing the spatial placement (left, right, middle, etc.). All animal species tested so far seem to employ both strategies, but some species (e.g. fish, rats and dogs) have a preference for locational strategies, while others (e.g. toads, chickens and children) favor those which use distinctive features. A comparison of the cognitive strategies of humans, chimpanzees, bonobos, gorillas, and orangutans, has revealed that all non-human great apes and 1-year-old human infants prefer a locational strategy, even when an object strategy would be more efficient. This suggests that the common ancestor of all great apes enacted a similar strategy preference in employing spatial memory. However, 3-year-old human children in these circumstances chose the more efficient strategy.
[1007] Haun, D. B. M., Call J., Janzen G., & Levinson S. C.
(2006). Evolutionary Psychology of Spatial Representations in the Hominidae.
Current Biology. 16(17), 1736 - 1740.
http://www.eurekalert.org/pub_releases/2006-09/cp-acs083006.php
http://www.eurekalert.org/pub_releases/2006-09/m-hdo090606.php
Genetic variations that may be key to the evolution of the human brain
It has been thought that most genetic variations between people and between species are due to small changes in the sequence of DNA lettering, but a new idea that’s becoming popular is that the number of copies of genes is an important source of variation that may be driving evolution. Comparison of the DNA sequences of humans, chimpanzees and monkeys, has now revealed that a gene that codes for a piece of protein called DUF1220 exists in 212 copies in humans, but only 37 in chimpanzees and 30 in monkeys. Mice and rats have only one. The protein is found in the heart, spleen, skeletal muscle, and small intestine, and particularly in brain regions associated with higher cognitive function.
[643] Popesco, M. C., MacLaren E. J., Hopkins J., Dumas L., Cox M., Meltesen L., et al.
(2006). Human Lineage-Specific Amplification, Selection, and Neuronal Expression of DUF1220 Domains.
Science. 313(5791), 1304 - 1307.
http://www.nature.com/news/2006/060828/full/060828-5.html
http://sciencenow.sciencemag.org/cgi/content/full/2006/831/4?etoc
An exploration of those 49 areas of the genome that have changed most between human and chimpanzee has revealed one area that's changed dramatically in a relatively short period of time. The gene is found only in mammals and birds, and hasn’t changed much in other animals — between a chimp and a chicken, there are only two differences in the 118 letters of DNA code that make up HAR1 (human accelerated region 1). But there are 18 differences in that one gene between human and chimp. That is a lot of change to happen in five million years. HAR1 is part of two overlapping genes -- both the rare RNA genes, not genes that code for proteins -- one of which (HAR1F) is active in nerve cells that appear early in embryonic development and play a critical role in the formation of the layered structure of the human cerebral cortex. The other also appears to be involved in cortical development.
[420] Siepel, A., Kern A. D., Dehay C., Igel H., Ares M., Vanderhaeghen P., et al.
(2006). An RNA gene expressed during cortical development evolved rapidly in humans.
Nature. 443(7108), 167 - 172.
http://news.yahoo.com/s/ap/20060817/ap_on_sc/brain_evolution
http://www.newscientist.com/article/dn9767?DCMP=NLC-nletter&nsref=dn9767
http://www.sciencedaily.com/releases/2006/08/060817102730.htm
Avoiding predators may be the reason for our large brains
A study of predators in Africa and South America suggests a new theory for why we evolved big brains. Apparently predators prefer prey with smaller brains, suggesting that more smarts help you outwit your enemies. A popular theory has been that the complexities of being social pushed the increase in brain size, and it does seem that this is also a factor, but predation is probably behind this as well — living in a group protects against predators, because group mates help keep an eye out for danger. However, the study found that while predators did prefer less sociable prey, the strongest pattern was for predators to prefer prey with relatively small brains. The researchers suggest that the need for a larger brain was strengthened when our primate ancestors came down out of the trees, and entered a much more dangerous environment.
[1325] Shultz, S., & Dunbar R. I. M.
(2006). Chimpanzee and felid diet composition is influenced by prey brain size.
Biology Letters. 2(4), 505 - 508.
http://www.guardian.co.uk/science/story/0,,1835615,00.html
Bigger brains associated with domain-general intelligence
Analysis of hundreds of studies testing the cognitive abilities of non-human primates provides support for a general intelligence, and confirms that the great apes are more intelligent than monkeys and prosimians. Individual studies have always been criticized for not clearly ensuring that one species wasn’t out-performing another simply because the particular testing situation was more suited to them. However, by looking at so many varied tests, the researchers have overcome this criticism. Although there were a few cases where one species performed better than another one in one task and reversed places in a different task, overall, some species truly outperformed others. The smartest species were clearly the great apes — orangutans, chimpanzees, and gorillas. Moreover, there was no evidence that any species performed especially well within a particular paradigm, contradicting the theory that species differences in intelligence only exist for narrow, specialized skills. Instead, the results argue that some species possess a broad, domain-general type of intelligence that allows them to succeed in a variety of situations.
Deaner, R.O., van Schaik, C.P. & Johnson, V. 2006. Do some taxa have better domain-general cognition than others? A meta-analysis of nonhuman primate studies. Evolutionary Psychology, 4, 149-196.
Full-text available at http://human-nature.com/ep/downloads/ep04149196.pdf
http://www.sciencedaily.com/releases/2006/08/060801231359.htm
Asymmetrical brains let fish multitask
A fish study provides support for a theory that lateralized brains allow animals to better handle multiple activities, explaining why vertebrate brains evolved to function asymmetrically. The minnow study found that nonlateralized minnows were as good as those bred to be lateralized (enabling it to favor one or other eye) at catching shrimp. However, when the minnows also had to look out for a sunfish (a minnow predator), the nonlateralized minnows took nearly twice as long to catch 10 shrimp as the lateralized fish.
[737] Dadda, M., & Bisazza A.
(2006). Does brain asymmetry allow efficient performance of simultaneous tasks?.
Animal Behaviour. 72(3), 523 - 529.
http://sciencenow.sciencemag.org/cgi/content/full/2006/623/2?etoc
Primates take weather into account when searching for fruits
In recent times, a popular hypothesis for why primates, and especially humans, have more strongly developed cognitive skills than other mammals, is that they result from the need for complex social skills. There is quite a lot of support for this argument. But it is not the only possibility and a recent study has looked at an alternative: that it evolved to deal with ecological problems, such as foraging for food. Researchers followed a group of wild gray-cheeked mangabeys from dawn to dusk over 210 days in their natural rainforest habitat, obtaining an almost complete record of their foraging decisions in relation to their preferred food, figs. The findings are consistent with the idea that monkeys make foraging decisions on the basis of episodic ("event-based") memories of whether or not a tree previously carried fruit, combined with knowledge of recent and present weather conditions and a more generalized understanding of the relationship between temperature and solar radiation and the maturation rate of fruit and insect larvae.
[493] Janmaat, K., Byrne R., & Zuberbuhler K.
(2006). Primates Take Weather into Account when Searching for Fruits.
Current Biology. 16(12), 1232 - 1237.
http://www.eurekalert.org/pub_releases/2006-06/cp-ptw061406.php
'Perception' gene tracked humanity's evolution
A gene thought to influence perception and susceptibility to drug dependence is expressed more readily in human beings than in other primates, and this difference coincides with the evolution of our species. The gene encodes prodynorphin, an opium-like protein implicated in the anticipation and experience of pain, social attachment and bonding, as well as learning and memory. Although the protein prodynorphin is identical in humans and chimps, in the gene's promoter sequence (that controls how much of the protein is expressed) some 10% is different (this compares to the overall 1 to 1.5% difference between human and chimpanzee genes). There is high genetic variation in the prodynorphin promoter among humans, but not among other primates. Variants have been tentatively linked to schizophrenia, cocaine addiction, and epilepsy. The report supports a growing consensus among evolutionary anthropologists that hominid divergence from the other great apes was fueled not by the origin of new genes, but by the quickening (or slowing) of the expression of existing genes.
[732] Rockman, M. V., Hahn M. W., Soranzo N., Zimprich F., Goldstein D. B., & Wray G. A.
(2005). Ancient and Recent Positive Selection Transformed Opioid cis-Regulation in Humans.
PLoS Biol. 3(12), e387 - e387.
Full text available at http://biology.plosjournals.org/perlserv/?request=get-document&doi=10.1371/journal.pbio.0030387
http://www.eurekalert.org/pub_releases/2005-11/iu-gt111405.php
Human brains still evolving
Two genes active in the brain — Microcephalin and ASPM — have now been sequenced. Both regulate brain size. The sequencing has revealed a distinctive mutation in both genes, both of which change the protein the gene codes for. For the Microcephalin gene, the mutation is now in the brains of about 70% of humans, and half of this group carry completely identical versions of the gene, suggesting the mutation arose recently (between 60,000 and 14,000 years ago) and spread quickly through the human species due to selection pressure, rather than accumulating random changes through neutral genetic drift. The new variant of ASPM appeared in humans even more recently — somewhere between 14,000 and 500 years ago — and is already present in about a quarter of people alive today.
[381] Evans, P. D., Gilbert S. L., Mekel-Bobrov N., Vallender E. J., Anderson J. R., Vaez-Azizi L. M., et al.
(2005). Microcephalin, a Gene Regulating Brain Size, Continues to Evolve Adaptively in Humans.
Science. 309(5741), 1717 - 1720.
[684] Mekel-Bobrov, N., Gilbert S. L., Evans P. D., Vallender E. J., Anderson J. R., Hudson R. R., et al.
(2005). Ongoing Adaptive Evolution of ASPM, a Brain Size Determinant in Homo sapiens.
Science. 309(5741), 1720 - 1722.
http://www.newscientist.com/article.ns?id=dn7974
http://www.sciencentral.com/articles/view.htm3?article_id=218392658
New light on speech evolution in humans
A new monkey study challenges thinking that speech developed as a result of new structures that evolved in the human brain. A distinct brain region that controls jaw movements in macaque monkeys has been found in the same area and with the same anatomical characteristics as Broca's area. The discovery suggests that this area of the brain evolved originally to perform high-order control over the mouth and the jaw, and that as humans evolved this area came to control the movements necessary for speech.
[1333] Petrides, M., Cadoret G., & Mackey S.
(2005). Orofacial somatomotor responses in the macaque monkey homologue of Broca's area.
Nature. 435(7046), 1235 - 1238.
http://www.eurekalert.org/pub_releases/2005-06/mu-nrp062905.php
Primitive brain learns faster than the "thinking" part of our brain
A study of monkeys has revealed that a primitive region of the brain known as the basal ganglia learns rules first, then “trains” the prefrontal cortex, which learns more slowly. The findings turn our thinking about how rules are learned on its head — it has been assumed that the smarter areas of our brain work things out; instead it seems that primitive brain structures might be driving even our most high-level learning.
[722] Pasupathy, A., & Miller E. K.
(2005). Different time courses of learning-related activity in the prefrontal cortex and striatum.
Nature. 433(7028), 873 - 876.
http://web.mit.edu/newsoffice/2005/basalganglia.html
Another clue to the evolution of the human brain
A new study suggests that the birth of a gene that fueled neurotransmission may have been a key advance in the evolution of the hominoid brain. GLUD2, a gene gene involved in glutamate metabolism, is found in humans and apes, but not in Old World monkeys, indicating that the gene appeared after monkeys and hominoids went their separate ways (some 23 million years ago), but before the gibbon lineage split from humans and great apes around 18 million years ago. Over time, GLUD2 acquired two amino acid changes that increased glutamate flux, possibly enhancing cognitive function in the hominoid brain.
[1277] Burki, F., & Kaessmann H.
(2004). Birth and adaptive evolution of a hominoid gene that supports high neurotransmitter flux.
Nat Genet. 36(10), 1061 - 1063.
http://www.biomedcentral.com/news/20040920/02
More support for social skill theory of brain evolution
Why do we have such large brains? Brains are very costly — they require a lot of energy. Gaining credence in recent years has been the idea that the advantage of our brain has been through the complex social skills it allows. Evidence supporting this has come from a study of records of primates deceiving each other for personal gain. The bigger the neocortex, it seems, the more likely a primate is to practice deception. The researchers gathered instances of deception across 18 species of primate and found no link with overall brain size, but a clear match between devious deeds and neocortex volume.
[838] Byrne, R. W., & Corp N.
(2004). Neocortex size predicts deception rate in primates..
Proceedings of the Royal Society B: Biological Sciences. 271(1549), 1693 - 1699.
http://www.guardian.co.uk/life/dispatch/story/0,12978,1250723,00.html
http://www.newscientist.com/news/news.jsp?id=ns99996090
More complex brain may have pre-dated Homo genus
New research supports Raymond Dart’s suggestion (in 1925) that the human brain started evolving its unique characteristics much earlier than has previously been supposed. One of the differences between human and ape brains is the position of the primary visual striate cortex (PVC), an area of the brain devoted exclusively to vision. In the ape brain, this is situated further forward than it is in human brains, making the PVC larger. It has been claimed that the PVC only decreased in size once the brain had grown substantially in size – when big-brained Homo (the hominid group that includes humans) appeared around 2.4 million years ago. However, new examination of an endocast of the brain of an Australopithecus africanus (Australopithecines pre-dated Homo, and their brains were similar in size to those of chimpanzees) has found evidence of a decreased PVC. This suggests an increase in the region lying in front of the PVC - the posterior parietal cerebral cortex, which is associated in humans with a variety of complex behaviors such as the appreciation of objects and their qualities, facial recognition and social communication.
[1379] Holloway, R. L., Clarke R. J., & Tobias P. V.
(2004). Posterior lunate sulcus in Australopithecus africanus: was Dart right?.
Comptes Rendus Palevol. 3(4), 287 - 293.
http://news.bbc.co.uk/1/hi/sci/tech/3496549.stm
Gene may be key to evolution of larger human brain
Researchers have now identified a gene that appears to have played a significant role in the expansion of the human brain's cerebral cortex. The gene is called the Abnormal Spindle-Like Microcephaly Associated (ASPM) gene, and dysfunction in this gene is linked to human microcephaly — a severe reduction in the size of the cerebral cortex. Comparison of the gene sequence in humans with that of 6 other primates (progressively less related to humans) revealed that the ASPM gene showed clear evidence of changes accelerated by evolutionary pressure in the lineage leading to humans, and the acceleration was most prominent in recent human evolution after humans diverged from chimpanzees (our closest primate relative) some five million years ago. A massive population-wide genetic change in the gene seems to have occurred in the human lineage every 300,000 to 400,000 years since then, with the last such change occurring between 200,000 and 500,000 years ago. Such strong evidence of evolutionary change is most unusual. No such change was found when other (non-primate) mammals were investigated.
[1199] Evans, P. D., Anderson J. R., Vallender E. J., Gilbert S. L., Malcom C. M., Dorus S., et al.
(2004). Adaptive evolution of ASPM, a major determinant of cerebral cortical size in humans.
Hum. Mol. Genet.. 13(5), 489 - 494.
http://www.eurekalert.org/pub_releases/2004-01/hhmi-gmb011204.php
Evolution of the mammalian brain
Two recent studies cast light on the evolution of the mammalian brain. A study of the brains of cetaceans, has found that that the cortex of a killer whale is dramatically more “folded” than that of an Amazon River dolphin (the deep and complex folding, or gyrification, of the cortex surface is what allows the human brain to have far more informational capacity than would be expected from its mass). The whales’ brain was particularly convoluted in the area of the corpus callosum, the main “bridge” between the hemispheres. In other comparative study of mammalian brains, it was found that the larger the brain, the larger the mean diameter of the axons. Axons were also less densely packed and more heavily myelinated. Across all species studied, fast cross-brain conduction times were maintained at 1-2 milliseconds.
Research presented at the 2003 annual meeting of the Society for Neuroscience, held November 8–12 in New Orleans, LA
Human frontal cortex not proportionately larger compared to great apes
Humans are widely considered to have a disproportionately large frontal cortex compared to other animals, and the disparity in cognitive capabilities is partly attributed to this difference. However, a comparison of the relative size of the frontal cortex in humans versus other great apes reveals that human frontal cortices are not disproportionately large in comparison to those of the great apes. The authors suggest that the human advantage may be due to differences in individual cortical areas and to a richer interconnectivity, rather than an overall size difference.
[955] Semendeferi, K., Lu A., Schenker N., & Damasio H.
(2002). Humans and great apes share a large frontal cortex.
Nat Neurosci. 5(3), 272 - 276.
http://www.nature.com/cgi-taf/DynaPage.taf?file=/neuro/journal/v5/n3/abs/nn814.html
Living in large groups could give you a better memory
A study into the brains of songbirds found that birds living in large groups have more new neurons and probably a better memory than those living alone. Does this have relevance for humans? We don't know yet, but it has been observed that social animals such as elephants tend to have better memories than loners.
[774] Lipkind, D., Nottebohm F., Rado R., & Barnea A.
(2002). Social change affects the survival of new neurons in the forebrain of adult songbirds.
Behavioural Brain Research. 133(1), 31 - 43.
http://www.eurekalert.org/pub_releases/2002-02/ns-lil022002.htm
Manipulating a signaling protein in a developing mouse brain caused radical changes in the cortex and may provide a clue about how the cerebral cortex changes in evolution
Using a newly developed technique, University of Chicago researchers have manipulated one of the signaling proteins in the developing mouse brain and found such manipulations cause radical changes in the cortex. Fibroblast Growth Factor 8 (FGF8), a member of a family of signaling proteins involved in forming other structures in the embryo, is normally found near the front of the developing cortex. Using a new microsurgical technique, the researchers were able to manipulate the amount and position of this signaling protein in the embryo and look for changes in the cortical pattern much later. The researchers increased the amount of the signaling protein in its normal position, decreased it by inserting a gene for a receptor able to soak up the protein, or expressed it in a new position. Each manipulation profoundly affected cortical area pattern. "Most dramatic, when a new source of the signaling protein was generated close to the back of the embryonic cortex, the whole program changed." The generation of a new cortical area by a molecular manipulation has not been seen before and may provide a clue about how the cerebral cortex changes in evolution. One way that evolution seems to generate more functionally complex brains is by adding new areas to the cortex.
[498] Fukuchi-Shimogori, T., & Grove E. A.
(2001). Neocortex Patterning by the Secreted Signaling Molecule FGF8.
Science. 294(5544), 1071 - 1074.
http://www.eurekalert.org/pub_releases/2001-09/uocm-anm091801.php