A simple method for determining cerebralization. Brain weight and intelligence

Krompecher, S; Lipák, J.

doi:10.1002/cne.901270108

Cited by 26 publications

(7 citation statements)

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“…Be cause of these differences, we conclude that ac is not always equal to av. Further more, the BS, which probably has the most somatic involvement of the three di visions [see Hofman, 1982;Krompecher and Lipak, 1966], generally varies by a lower exponent than the other two divi sions. If av were greater than ac, then the more somatic divisions would vary by a higher exponent.…”

Section: Discussionmentioning

confidence: 99%

Allometry of Major CNS Divisions: Towards a Reevaluation of Somatic Brain-Body Scaling

Fox

Wilczynski²

1986

Brain Behav Evol

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For each of four rodent species, average weights for the brainstem, cerebellum, and forebrain were determined and average cross-sectional area of the cervical spinal cord (SCA) was calculated. Linear regression analyses against log body weight were performed on these data (log translated), along with data (except SCA) from the literature for insectivores and primates. Results indicate that the different CNS divisions scale by different powers of body weight in different mammals and that the rodent SCA varies by less than the 2/3 power of body weight. Based on the results, we conclude that (1) there are at least two general brain scaling factors, somatic and nonsomatic, that necessitate a more complex general allometric equation; (2) the exponent for somatic brain scaling is approximately 0.52, and (3) body surface area is not a primary determinant of brain size.

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Section: Discussionmentioning

confidence: 99%

Allometry of Major CNS Divisions: Towards a Reevaluation of Somatic Brain-Body Scaling

Fox

Wilczynski²

1986

Brain Behav Evol

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“…A study of the size of the brain in relation to body size has been employed chiefly in comparisons between species, in an effort to show how preeminent the brain has become in man. It was Cuvier who first introduced the concept of relative brain weight, that is, the weight of the brain expressed as a fraction of the weight of the body (Krompecher and Lipak 1966). Cobb's picture of a small human female standing alongside a rhinoceros shows graphically the difference in relative sizes of brains.…”

Section: Brain Size and Body Sizementioning

confidence: 99%

“…Because man, the sapient, did not come out at the top, it is not surprising that man, the vainglorious and the arrogant, has been searching ever since for a variety of strange indices that would place him unequivocally and unassailably on the highest branch of the tree of life. For example, when the length of the hypothalamus is expressed as a fraction of that of the cerebrum, man has the lowest fraction, and so comes out on top (Kunnner 1961); when the weight of the spinal cord is expressed as a fraction of the brain weight, man has the lowest fraction, and so conies out on top (Latimer 1950; Krompecher and Lipak 1966); when the cranial capacity is related to the area of >J( .06 Cobb 1965) Tamarin (Leontocebus) 1 : 19 100.000 the foramen magnum, man has the highest value, and still ends up on top (Radinsky 1967)! All the indices I have cited have a certain though limited usefulness when comparisons are made between one species and another.…”

Section: Brain Size and Body Sizementioning

confidence: 99%

The brain in hominid evolution

Tobias¹

1971

355

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Witwatersrand University, labeled 260 c.c. (for the half-volume). A cast of this reconstructed endocast was presented by Dart to University College, London, where Zuckerman (1928) determined the volume of the total endocast to be 500 c.c. Dart's (1929) paper cited no figure for the capacity. Keith stated that he had made "an exact model of half the brain" in plasticine. It measured 225 c.c, giving 450 c.c. for the whole as "a minimum size." Nevertheless, he was prepared to take 500 c.c. as "an impartial estimate," and, in addition, he used the figure of 500 c.c. in computing the "adult size" for Taung (Keith 1931, pp. 61-65). Two decades after the first publication Schepers (1946) attempted further reconstructions and reported that they "gave results which varied but little from this figure (500 c.c.)," which he stated, not quite precisely, was that earlier claimed for it by Dart. As mentioned above, Dart's original claim was 520 c.c. In fact, Schepers used the figure of 500 c.c. in his text (p. 238) and of 520 c.c. in his Table 1 (p. 242). Le Gros Clark in 1947 stated that "Zuckerman's estimate of 500 c.c. is sufficiently close [to Dart's original estimate] to be taken as confirmatory" (Le Gros Clark 1947, p. 313). Still later, Le Gros Clark (1964, p. 133) described the capacity as "rather more than 500 c.c." On the basis of these estimates by Dart, Zuckerman, Schepers, and Le Gros Clark, I have cited 500 to 520 c.c. for the volume in my tables of estimates of australopithecine cranial capacities (Tobias 1963, 1967a). Working in our Anatomy Department, Dr. R. L. Holloway, Jr. has recently reopened the question of the cranial capacity of the Taung child, and his new provisional reconstruction gives a smaller value.* With estimates ranging on either side of 500 c.c, it would seem to be safest, for the time being, to accept 500 c.c as an approximation of the cranial capacity of the Taung child. The problem now arises of what cranial capacity the Taung individual would have attained had he lived to adulthood. Dart was keenly aware of • Since the James Arthur Lecture was delivered, Holloway (1970b) has published his new estimate for the endocranial capacity of the Taung child. Based on new reconstructions made by him in the Anatomy Department in 1969, he has arrived at a figure of 405 c.c, the mean of the capacities of his 2 most accurate reconstructions. This figure is well below the figure of 500 to 520 c.c. accepted by most workers up to the present but is closer to Sir Arthur Keith's original rough estimate of "less than 450 c.c." When Holloway s estimate of 405 c.c. is corrected for the juvenile age of the Taung child, he obtains an adult estimate of 440 c.c, exactly 100 c.c. less than the latest adult estimate based on the old reconstruction.

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“…Larger bodies are generally believed to require a larger number of sensory and motor neurons to operate them (Jerison, 1973; Fox and Wilczynski, 1986). In particular, the larger the muscle mass of an individual or species, the larger one expects the motor neuron pool that controls it to be (Krompecher and Lipák, 1966). However, what is the numerical relationship between numbers of neurons and muscle mass across species (and individuals), and how is it determined?…”

Section: Introductionmentioning

confidence: 99%

What Determines Motor Neuron Number? Slow Scaling of Facial Motor Neuron Numbers With Body Mass in Marsupials and Primates

Watson¹,

Provis²,

Herculano‐Houzel³

2012

The Anatomical Record

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How does the number of motor neurons in the brain correlate with the muscle mass to be controlled in the body? Numbers of motor neurons are known to be adjusted during development by cell death, but the change in the percentage of surviving motor neurons in response to experimental changes in target muscle mass is relatively small. Here we address the quantitative matching between final numbers of motor neurons in the facial nucleus and body mass (which we use as a proxy for the muscle mass). In 22 marsupial species, we found that the number of facial motor neurons is strongly correlated with body mass, and scales across species as a power function of body mass with a very small exponent of 0.184, which is close to the exponent found in primates from previously published data. With such an exponent, doubling the body mass is accompanied by a modest increase of only 14% in numbers of facial motor neurons, while halving body mass results in a decrease of only 12%. These numbers are remarkably similar to the 15-20% increase or 8% decrease in the number of spinal cord motor neurons that results from experimental or natural doubling or reducing by half the target muscle field of birds and amphibians. The scaling rule presented here might thus account for the quantitative matching of motor neurons to their target muscle mass in evolution. With this small scaling exponent, our data also raise the possibility that larger animals will have larger motor units.

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A simple method for determining cerebralization. Brain weight and intelligence

Cited by 26 publications

References 4 publications

Allometry of Major CNS Divisions: Towards a Reevaluation of Somatic Brain-Body Scaling

Allometry of Major CNS Divisions: Towards a Reevaluation of Somatic Brain-Body Scaling

The brain in hominid evolution

What Determines Motor Neuron Number? Slow Scaling of Facial Motor Neuron Numbers With Body Mass in Marsupials and Primates

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