Re the blog article cited by Chris Green: http://www.dictionaryofneurology.com/2012/01/dogmas-in-neuroscience-and-further.html
>ever wonder where we got the idea that humans >have about 100 billion neurons?". Thanks Chris, I never knew that. :-) >From the article: "Sweeping histories, grand narratives, and big stories have long been the stock-in-trade of popular histories. (H. G. Well's Outline of History, a wonderful book by the way, is but one example.) But such histories have a way of hardening ideas and dogmas that are actually controversial or in need of refinement and elaboration even as the question of scientific facticity (as the comments about dementia above make clear) has considerable importance." This seems to me to be a matter of popular misconceptions rather than dogmas, and, of course, is far from being confined to grand narratives or popular histories. One of my pet grouses is that so many book reviewers seem to accept general contentions made in various non-fiction books without questioning them, no doubt on the grounds that the author seems to have made a good case. But it should be obvious that authors out to make a case may have a tendency to be selective in the evidence they provide for the reader – not to mention that what they do provide may be tendentiously presented. I'll refrain from giving several examples from my pet topics, though the widely acclaimed best-seller by Jeffrey Masson, *The Assault on Truth*, that purported to reveal a shameful episode in Freud's early psychotherapeutic career immediately jumps to mind as a classic example of this: http://snipurl.com/21rh6p9 This example indicates that the implied warning in the above quoted paragraph applies just as much to fresh narratives that supposedly undermine a previously widely held view and gain wide currency. Allen Esterson Former lecturer, Science Department Southwark College, London allenester...@compuserve.com http://www.esterson.org -------------------------------------------------- From: Christopher D. Green <chri...@yorku.ca> Subject: The Neuro Times: Dogmas in Neuroscience and Further Thoughts on the Limits of Neurohistory Date: Tue, 17 Jan 2012 15:05:13 -0500 While we like to ponder the origin of psychological fallacies (like using only 10% of our brains), there are many others that we probably continue to espouse, but do not recognize. For instance, every wonder where we got the idea that humans have about 100 billion neurons? See here: http://www.dictionaryofneurology.com/2012/01/dogmas-in-neuroscience-and-further.html and the followup column: http://www.dictionaryofneurology.com/2012/01/so-how-many-neurons-do-you-have.html (Thanks to Vinny Hevern of Lemoyne College in Syracuse for bringing this to my attention.) Regards, Chris -- Christopher D. Green Department of Psychology York University Toronto, ON M3J 1P3 Canada ------------------------------------------------ From: Michael Palij <m...@nyu.edu> Subject: re: The Neuro Times: Dogmas in Neuroscience and Further Thoughts on the Limits of Neurohistory Date: Tue, 17 Jan 2012 17:00:13 -0500 On Tue, 17 Jan 2012 12:03:46 -0800, Christopher D. Green wrote: >While we like to ponder the origin of psychological fallacies (like >using only 10% of our brains), there are many others that we probably >continue to espouse, but do not recognize. Are you saying that the assertion that are 100 billion neurons in the human brain is the equivalent of saying that we only use 10% of our brains? If so, I call shenanigans. >For instance, every wonder where we got the idea that humans have about >100 billion neurons? Probably from my undergraduate physiological psychology textbook. For example, Richard Thompson's (1985) "The Brain" states that there are 100 billion neurons (see page 2). But I actually took physio in the early 1970s and I think we used a copy of Thompson's regular text book back then. In any event, I remember that there was uncertainty about the exact number. Somebody should look at physiological psych textbooks and review how the number has changed over time. >See here: >http://www.dictionaryofneurology.com/2012/01/dogmas-in-neuroscience-and- further.html >and the followup column: >http://www.dictionaryofneurology.com/2012/01/so-how-many-neurons-do-you- have.html The two blog entries I believe rely upon the following article: http://onlinelibrary.wiley.com/doi/10.1111/j.1460-9568.2011.07923.x/abstract As reported in the Lent et al article, they cite Hubel as one source, but consider this quote from Lent et al.: |‘The mature brain is composed of 100 billion to 200 billion |neurons and perhaps 10 times as many glial cells’ (Hubel, 1979) | |The ‘magic number’ of 100 billion neurons in the human brain has |been widely sustained in papers (Hubel, 1979; Fischbach, 1992; Noctor |et al., 2007) and textbooks (Kandel et al., 2000;Bear et al., 2007; Purves |et al., 2008), although a broad range is arbitrarily adopted, from10 billion |to 1 trillion (reviewed by Soper & Rosenthal, 1988). However, little |direct evidence for it has been produced. In fact, stereological estimates |have yielded numbers of 3 billion, 7 billion, 14 billion, 19–23 billion, |21–26 billion and 28–39 billion neurons for the cerebral cortex |(Pakkenberg, 1966; Pakkenberg & Gundersen, 1997; more extensively |reviewed by Azevedo et al., 2009). The same has been the case for |the cerebellum, for which counts have produced numbers from 70 billion |to 109 billion neurons (Lange, 1975; Andersen et al., 1992, 2003). So the estimates of the number of neurons in the brain actually vary and it appears that 100 billion is used as a simple indicator of the possible number -- this would be a good situation for providing the range of values. It's unclear why Lent et al refer to 100 billion as a "magic number". The Lent et al article reminds me of another article I am familiar with, a 1988 chapter in the Annual Review of Neuroscience by Williams and Harrup titled "The Control of Neuron Number". There is one paragraph that is of particular interest and I quote it here: |Total Neuron Number |The total number of neurons in the central nervous system ranges from |under 300 for small free-living metazoans such as rotifers and nematodes |(Martini 1912, Bullock & Horridge 1965), through about 30 million for |the common octopus and small mammals such as shrews (Young 1971, |Campbell & Ryzen 1953), to well over 200 billion for whales and elephants. |Estimates for the human brain range between 10 billion and 1 trillion. The |imprecision in these estimates is due almost entirely to uncertainty about |the number of granule cells in the cerebellum, a problem that can be traced |back to a study by Braitenberg & Atwood (1958). More recent work by |Lange (1975) makes a reasonably accurate estimate possible: The average |human brain (1350 gm) contains about 85 billion neurons; of these, 12 to |15 billion are telencephalic neurons (Shariff 1953), 70 billion are cerebellar |granule cells (Lange 1975), and fewer than 1 billion are brainstem and |spinal neurons. (p423-424) So, Williams and Harrup provide an even greater range for the human brain, from 10 billion to 1 trillion. One starts to wonder why Lent et al are calling the "100 billion neuron" number a dogma when there clearly are sources that provide variations. Of course, one could argue that Lent et al are not really interested in "dogma" but instead are more interested in presenting the results of their new method for estimating the number of neurons. How many neuron do they estimate? Quoting from their article: |Using the isotropic fractionator, we contributed to reducing the |uncertainty of these numbers (Azevedo et al., 2009) – absolute counts |yielded an average of 86 billion neurons in male human brains |50–70 years old (Fig. 3), about 15% less than the ‘magic number’. So, Lent et al argue for 86 billion against 100 billion but Williams and Harrup argue for 85 billion. Interestingly, Lent et al cite the Williams and Harrup article but not in the context of the number of neurons, instead it is in the context of another "myth". Perhaps Lent et al did not read the chapter closely. Then again, perhaps this is much ado about nothing. Consider the following case that was described in the journal "The Lancet" and imagine how many neurons are involved here? http://www.thelancet.com/journals/lancet/article/PIIS0140-6736%2807%2961127-1/fulltext I love this short article because it shows how plastic the brain is though I wonder what it says about French civil servants. ;-) -Mike Palij New York University m...@nyu.edu --- You are currently subscribed to tips as: arch...@jab.org. To unsubscribe click here: http://fsulist.frostburg.edu/u?id=13090.68da6e6e5325aa33287ff385b70df5d5&n=T&l=tips&o=15401 or send a blank email to leave-15401-13090.68da6e6e5325aa33287ff385b70df...@fsulist.frostburg.edu
