<article_title>Brain</article_title>
<edit_user>200.1.109.3</edit_user>
<edit_time>Thursday, August 5, 2010 4:22:51 PM CEST</edit_time>
<edit_comment>/* Vertebrates */</edit_comment>
<edit_text>The relationship between brain size, body size and other variables has been studied across a wide range of vertebrate species. Brain size increases with body size but not proportionally. Averaging across all orders of mammals, it follows a power law, with an exponent of about 0.75.&lt;ref&gt;Armstrong, 1983&lt;/ref&gt; This formula applies to the average brain of mammals but each family departs from it, reflecting their sophistication of behavior.&lt;ref&gt;Jerison, Evolution of the Brain and Intelligence&lt;/ref&gt; For example, primates have brains 5 to 10 times as large as the formula predicts. Predators tend to have larger brains. When the mammalian brain increases in size, not all parts increase at the same rate. The larger the brain of a species, the greater the fraction taken up by the <strong><strike>cortex</strike></strong><strong>[[cortex]]</strong>.&lt;ref name=&quot;Finlay&quot;&gt;Finlay et al., 2001&lt;/ref&gt;</edit_text>
<turn_user>Tryptofish<turn_user>
<turn_time>Wednesday, August 4, 2010 9:10:25 PM CEST</turn_time>
<turn_topicname>Primate brain</turn_topicname>
<turn_topictext>Actually, it is pretty well established, based on single-unit studies that show visual responsiveness, that more than half the primate neocortex (not brain) is dedicated to vision. See, for example: Sereno, M.I., A.M. Dale, J.B. Reppas, K.K. Kwong, J.W. Belliveau, T.J. Brady, B.R. Rosen, and R.B.H. Tootell (1995) Borders of multiple visual areas in human revealed by functional magnetic resonance imaging. Science 268:889-893. http://www.cogsci.ucsd.edu/~sereno/papers/HumanRetin95.pdf Where they state "Over half of the neocortex in non-human primates is occupied by visual areas. At least 25 visual areas beyond the primary visual cortex (V1) have been identified with a combination of microelectrode mapping, tracer injections, histological stains, and functional studies (1)." Their references for this claim are: M.I. Sereno and J.M. Allman, in The Neural Basis of Visual Function, A.G. Leventhal Ed.(Macmillan, London, 1991), pp. 160-172 J.H. Kaas and L.A. Krubitzer, Neuroanatomy of Visual Pathways and their Retinotopic Organization, B. Dreher and S.R. Robinson Eds. (Macmillan, London, 1991), pp. 302-359 D.J. Felleman and D.C. Van Essen, Cereb. Cortex 1, 1 (1991) M.G.P. Rosa, J.G. Soares, M. Fiorani Jr, R. Gattass, Vis. Neurosci. 10, 827 (1993). In humans, due to the increase in the size of the parietal and pre-frontal cortex, this number is probably lower than in our primate cousins. See, for example, for the cross-species comparisons Van Essen, D.C. Lewis, J.W,. Drury, H.A., Hadjikhani, N., Tootell, R.B., Bakircioglu, M. and Miller, M.I. (2001) Mapping visual cortex in monkeys and humans using surface-based atlases. Vision Research 41: 1359-1378. http://brainmap.wustl.edu/resources/VE_VisRes01.pdf Cheers, Edhubbard (talk) 20:34, 4 August 2010 (UTC) Thanks for that, much better now. There's a big difference between half of the brain and half of the neocortex. --Tryptofish (talk) 21:10, 4 August 2010 (UTC) Sure no problem... I'm renaming this section because it's worth mentioning that the references here, especially by people like Sereno, Felleman, Kaas, etc. are also good refs for the differential expansion of the frontal cortex in humans, relative to our other great ape/primate ancestors. I was going to add the Van Essen paper that I've cited above for the frontal cortex expansion, but there are probably other citations that would be good too (also, I think my ref format was incorrect for this page, but a badly formatted ref is better than none at all). Others who would be relevant to look at here are Patricia Goldman-Rakic, Joaquin Fuster (see his book: The Prefrontal Cortex 978-0123736444) and others who study the function of the pre-frontal cortex. There is some debate about the degree to which human frontal cortex differs from other great apes (see, Semendeferi, K., Lu, A., Schenker, N., and H. Damasio. 2002. Humans and great apes share a large frontal cortex. Nature Neuroscience. 5:272-276.) but there is little doubt that human frontal cortex is larger than in macaques. Another good, general source for these types of things would be Georg F. Striedter and his book Streidter, G.F. (2005). Principles of Brain Evolution Sinauer Associates, Sunderland, MA. ISBN 978-0878938209. Cheers, Edhubbard (talk) 21:36, 4 August 2010 (UTC)</turn_topictext>
<turn_text>Thanks for that, much better now. There's a big difference between half of the brain and half of the neocortex. </turn_text>