SIZE DOESN'T MATTER?: It may not be the size of the brain but its organization that matters when it comes to cognitive function.
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Research has shown that lead kills neurons (nerve cells), resulting in smaller brains. It has long been hypothesized that such changes in the brain caused by childhood lead exposure may be behind a higher incidence of poor cognitive performance and criminal behavior. And although it is difficult to disentangle the confounding effects of race, class and economics, a recent study by Kim Dietrich, a professor of environmental health at the University of Cincinnati, found that individuals who suffered from the highest lead exposure as children had the smallest brain sizes—as well as the most arrests.
"That early lead exposure was associated with smaller volumes of cortical gray matter [the parts of the brain rich in neural cell bodies and synapses] in the prefrontal area," he says. "And the fact that we saw both criminal behavior and volume loss in this critical area for executive function is probably more than just a coincidence."
That may be so, however, new scientific studies across several animal species, including humans, are challenging the notion that brain size alone is a measure of intelligence. Rather, scientists now argue, it is a brain's underlying organization and molecular activity at its synapses (the communication junctions between neurons through which nerve impulses pass) that dictate intelligence.
Two years ago, Paul Manger, a professor of health sciences at the University of the Witwatersrand in Johannesburg, South Africa, caused quite a stir when he referred to the beloved bottlenose dolphin, owner of a large, nearly human-size brain, as "dumber than a goldfish."
"When you look at cetaceans, they have big brains, absolutely," Manger says. "But if you look at the actual structure of the brain, it's not very complex. And brain size only matters if the rest of the brain is organized properly to facilitate information processing."
He argues that the systems within the brain—how neurons or nerve cells and synapses are organized—are the keys to determining information-processing capacity. Manger speculates that cetacean brains are large not because of intelligence but instead due to an abundance of fatty glial cells (non-nerve cells serving as a supporting tissue), which may be present to provide warmth in cold waters for the information-processing neurons in the brain's interior.
Mark Uhen, a vertebrate paleontologist at the Alabama Museum of Natural History, and Lori Marino, a biologist who studies brain evolution of cetaceans and primates at Emory University's Yerkes National Primate Research Center, disagree. Marino says that Manger's theories discount years of behavioral evidence that show dolphins to be complex thinkers. What's more, she says, the mammals have an unusual brain structure with a different functional map and therefore cannot be compared with other species.
Marino believes that the dolphin's unique brain organization may represent an alternate evolutionary route to complex intelligence—and that molecules released in synapses may provide that alternative path.
A study recently published in Nature Neuroscience by Seth Grant, a neuroscientist at the Wellcome Trust Sanger Institute in Cambridge, along with Richard Emes, a professor in Bioinformatics at Keele University School of Medicine in North Staffordshire, both in England, suggests that all species have the same basic proteins that act in the synapses.
"If you look at us and fish, we have very different cognitive abilities," Emes says. "But we have roughly the same number of these synaptic proteins. It is the number of interactions and gene duplications of these proteins that provide the brain building blocks for higher level cognitive function.”
Emes, Grant and colleagues agree with Marino and Uhenthat intelligence and differences between species are due to molecular complexity at the synaptic level. "The basic dogma says that the computational properties of the brain are based on the number of neurons and synapses," Grant says. "But we modify that by saying that the molecular complexity within those synapses is also important."
Grant and Emes looked at where approximately 150 synaptic proteins were released in the nervous systems of yeast, fruit flies and mice. They found that a variation in production and distribution patterns was linked to higher-level brain organization.
"The proteins that you find in yeast are the sort of proteins that are far more likely to be found expressed throughout the brain in uniform quantities," Grant says. "They laid a foundation to make more diverse and different regions of the brain using different combinations and expressions of other, more innovative proteins." He likens these molecular proteins to implements in a toolbox that help to build specialized brain regions. He goes on to say that the different interactions, duplications or deletions of these proteins resulted over time in the evolutionary development of regions like the prefrontal cortex in humans which is involved in higher executive function like planning and goal-directed behavior
Grant says that this finding offers scientists a new way to approach the study of brain evolution and intelligence and, perhaps more importantly, suggests that looking at sheer brain size has very little to offer in understanding cognitive abilities.
"It's clear now that there are wonderful mental abilities in birds even with their relatively small brains, nerve cells and neural connections. But they have complex molecular synapses," says Grant. "My sense is in the next 10 to 20 years our perspectives about the mental capacities of different species will change quite radically."
But the idea that a big brain equals big smarts is not going to go away anytime soon. Though Manger discounts the role of glial cells in intelligence, a posthumous anatomical study of Albert Einstein's brain showed that the scientific genius's brain differed from the brains of other dead scientists only with its greater ratio of glial cells to neurons. But a study of Einstein's brain organization and synaptic molecule configuration still remains to be completed.
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16 Comments
Add CommentVery interesting it's not the size of the brain but,whats in it.I have noticed bigheads are not as intelligent as modest people.
Reply | Report Abuse | Link to thisDear Readers,
Reply | Report Abuse | Link to thisI would like to correct and comment on several points in the article by Kayt Sukel. First, she states that the brain of the bottlenose dolphin is "nearly" the size of the human brain. That is wrong. The bottlenose dolphin brain is larger than the human brain. The average size of an adult human brain is 1250-1300 cc. The average size of an adult bottlenose dolphin brain is 1500 cc. Second, I am a proud faculty member in the Living Links Center led by Frans De Waal. This Center is housed at Yerkes but does not engage in invasive research with primates. I do not wish to be associated with Yerkes without the qualification that it is with this Center. Third, while not incorrect, the fact that dolphins are "beloved" is irrelevant to the scientific issue. I do not think it furthers the argument in any way to refer to this animal in this way in this context. In fact, it encourages the notion that the only reason one might disagree with Manger is because one loves dolphins. That is not the case. The debate is a scientific one that should be (and has been) settled on scientific grounds.
Thank you.
Sincerely,
Lori Marino, Ph.D.
Senior Lecturer
Neuroscience and Behavioral Biology Program
Emory University
WELL SAID DR. MERINO.
Reply | Report Abuse | Link to thisSORRY, DR. MARINO.
Reply | Report Abuse | Link to this
Reply | Report Abuse | Link to thisDear Dr. Merino,
I would like to comment on your third point. While it may not add to the scientific argument, it obviously does not take away. Being an article and not a strict expository writing, the writer has a right to artistic liberty as long as it does not mar the information with unneeded bias. I would also like to say that I love dolphins and I think that anyone on a scientific website such as this in a scientific community would not be so ignorant as to let their love of water-creatures come in between logic and fact, therefore making your fears a bit unwarranted.
Sincerely,
Ms Ariel Marie, No Degree
16 Year Old Girl
Missarielmarie@ymail.com
* Dr. Marino
Reply | Report Abuse | Link to thisThe article by Kayt, though interesting, is sadly incomplete.
Reply | Report Abuse | Link to thisFirst and foremost, we, as humans, have a bias in defining or understanding what 'intelligence' is. Accordingly all our so called intelligence tests are oriented towards a Homo sapiens friendly type of scoring. If we design a test that favors a mosquito for example,it may score above humans! Please read Prof. P. Patton (2008) for more on this.
If we consider biological evolution as a basis and see how creatures evolved, we find that evolution (a response to nature's stress) is more towards conserving one's own 'expended energy.' This conservation of expended energy provides a definition for 'comfort' too. Whether it is bipedal locomotion from that of quadruped, cooking food for easier digestion what is involved is saving energy.
Taking a cue form the above, we may define intelligence as the capacity of a creature in quickly assessing a situation (in order to take appropriate steps to enhance its own survival) utilizing a 'minimum of its own energy.'
Such an 'expended energy based index' for intelligence may depend on the brain's architecture, neurogenesis, neural connectivity, connectomes, role of glial cells (the role of astrocytes is just being investigated) etc. rather than just brain size.
Re: "... a recent study by Kim Dietrich, a professor of environmental health at the University of Cincinnati, found that individuals who suffered from the highest lead exposure as children had the smallest brain sizes—as well as the most arrests."
Reply | Report Abuse | Link to thisSo, exactly How did they determine brain sizes? Did they do CT scans of all these folks or what??
Is the phrenology a science to be considered regarding the brain? Since some people have areas of the brain more developed than others, would that help them to have a better use or more powerful brain's areas. How we can relate it with the abilities and characteristics of each area. This is something that I would like to read in the magazine.
Reply | Report Abuse | Link to thisIs the phrenology a science to be considered regarding the brain? Since some people have areas of the brain more developed than others, would that help them to have a better use or more powerful brain's areas. How we can relate it with the abilities and characteristics of each area. This is something that I would like to read in the magazine.
Reply | Report Abuse | Link to thisHow does one get exposed to lead? and how can we prevent that?
Reply | Report Abuse | Link to thisSo far none has been able to make a clear comparison and describe the relation between the size of a brain and its intelligence. The brain remains mystic to scientists as well as to spirtualists and yogis.
Reply | Report Abuse | Link to thisHowever, I'd like to start a discussion and issue research topics entitled "babies' brain intelligence"..."babies brain?where are you"... "brain embryo before 3"..."real brain in a virtual world"..."virtual brain in a real world"..."real mind in a virtual world"..."virtual mind in a real world"..."mind materialised"..."mind dwells in matter"... it is an endless list.
What is common in all is one fact.
The brain is a material object that we can touch while the mind is not. Since intelligence is something that we can't touch then it is associated with the mind which is a non-material object. To understand intelligence we have to invite the mind and question it. To observe the relation between the size of the brain and intelligence as if you are observing a wave in an ocean. Trying to interpret such an observation is as watching an everlasing movie of which the observer is a part of that movie. Oh! what a game is it. What a movie we are living in.
Merlin
NaturalTherapist
montreal, Quebec
http://www.24montreal.org
http://www.24yahoo.com
What a great article.
Reply | Report Abuse | Link to thisI am pleasantly suprised that such a long held tenet of the Darwinist paradigm is being questioned here.
Reply | Report Abuse | Link to thisI thought it was quite obvious that Amphioctopus marginatus creating portable armour out of coconut shells was more intelligent than a pod of whales getting beached yet again...
So are we going to see a reshuffling of the old Australopithecene to Homo Sapiens rogues gallery to include a few shards of bone reconstructed into man apes with bigger although less complex brains than their decendants?
Intelligence in nature was put there by intelligence. I am not going to do a Francis Crick and cry 'seeding', simply postponing the problem, but point you towards a wonderful Creator.
It may not be common knowledge but there is a highly intelligent life form on this planet that surpasses that of humans, but prefers to occupy a space in time other than we humans do
Reply | Report Abuse | Link to thisAs I recall, it is not so much the size of the brain in vertebrates that determines what may be described as the intellect, but the ratio of the size of the brain to the spinal cord. The percentage of the brain used to control bodily functions and core survival and reproductive behaviors (the 4 F's... fighting, fleeing, feeding and fornication) as apposed to purely the pursuit of knowledge unrelated to survival of the species, has not been addressed.
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