Cerebral Asymmetry and Human Uniqueness

Corballis, Michael C.

doi:10.1016/s1936-8526(07)05001-4

Cited by 7 publications

(6 citation statements)

References 89 publications

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“…Some researchers adhere to the hypothesis that hand preference in humans is stronger than any hand or limb preference in non-human species [12]. By extrapolation, it has also been argued that brain lateralization is stronger in humans, thereby adhering to a view of a significant discontinuity of brain function between humans and other animals [13,14] but see [15]. Although there is some support for this idea when only the evidence for hand preference in primates is considered, that too has been contested [14,16].…”

Section: Introductionmentioning

confidence: 99%

“…By extrapolation, it has also been argued that brain lateralization is stronger in humans, thereby adhering to a view of a significant discontinuity of brain function between humans and other animals [13,14] but see [15]. Although there is some support for this idea when only the evidence for hand preference in primates is considered, that too has been contested [14,16]. In fact, we now know that limb preferences present as population-level asymmetries are quite common in vertebrate species [12].…”

Section: Introductionmentioning

confidence: 99%

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Brain Size Associated with Foot Preferences in Australian Parrots

Kaplan

Rogers

2021

Symmetry

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Since foot preference of cockatoos and parrots to hold and manipulate food and other objects has been associated with better ability to perform certain tasks, we predicted that either strength or direction of foot preference would correlate with brain size. Our study of 25 psittacine species of Australia found that species with larger absolute brain mass have stronger foot preferences and that percent left-footedness is correlated positively with brain mass. In a sub-sample of 11 species, we found an association between foot preference and size of the nidopallial region of the telencephalon, an area equivalent to the mammalian cortex and including regions with executive function and other higher-level functions. Our analysis showed that percent left-foot use correlates positively and significantly with size of the nidopallium relative to the whole brain, but not with the relative size of the optic tecta. Psittacine species with stronger left-foot preferences have larger brains, with the nidopallium making up a greater proportion of those brains. Our results are the first to show an association between brain size and asymmetrical limb use by parrots and cockatoos. Our results support the hypothesis that limb preference enhances brain capacity and higher (nidopallial) functioning.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Brain Size Associated with Foot Preferences in Australian Parrots

Kaplan

Rogers

2021

Symmetry

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“…For instance, it is not known whether the significant increase in neuropil space observed in the human prefrontal cortex is specific to this region or is a more general trend that is common to other higher-order association areas. In addition, hemispheric lateralization of neuropil has never been studied across multiple areas of the cerebral cortex of human or chimpanzee brains within the same analysis, making it difficult to reach conclusions about the evolution of neuroanatomical asymmetry patterns as they relate to lateralized functions such as communication, language, and the control of manual actions (Corballis, 2007; Hopkins and Cantalupo, 2004; Hopkins et al, 2007; Hopkins et al, 2008; Hopkins et al, 2010). …”

Section: Introductionmentioning

confidence: 99%

Neuropil distribution in the cerebral cortex differs between humans and chimpanzees

Spocter

Hopkins

Barks

et al. 2012

J of Comparative Neurology

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Increased connectivity of higher-order association regions in the neocortex has been proposed as a defining feature of human brain evolution. At present, however, there are limited comparative data to examine this claim fully. We tested the hypothesis that the distribution of neuropil across areas of the neocortex of humans differs from that of one of our closest living relatives, the common chimpanzee. The neuropil provides a proxy measure of total connectivity within a local region because it is comprised mostly of dendrites, axons, and synapses. Using image analysis techniques, we quantified the neuropil fraction from both hemispheres in six cytoarchitectonically defined regions including frontopolar cortex (area 10), Broca’s area (area 45), frontoinsular cortex (area FI), primary motor cortex (area 4), primary auditory cortex (area 41/42), and the planum temporale (area 22). Our results demonstrate that humans exhibit a unique distribution of neuropil in the neocortex compared to chimpanzees. In particular, the human frontopolar cortex and the frontoinsular cortex had a significantly higher neuropil fraction than the other areas. In chimpanzees these prefrontal regions did not display significantly more neuropil, but the primary auditory cortex had a lower neuropil fraction than other areas. Our results support the conclusion that enhanced connectivity in the prefrontal cortex accompanied the evolution of the human brain. These species differences in neuropil distribution may offer insight into the neural basis of human cognition, reflecting enhancement of the integrative capacity of the prefrontal cortex.

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“…A few years ago, I engaged in a somewhat acerbic debate with Crow on the existence of lateralization in non-human animals (Crow 2004;Rogers 2004; see comments by Corballis 2007). Crow firmly adhered to the earlier, widely held notion that directional asymmetry is unique to modern Homo sapiens and saw it, in association with right-handedness, as the pivotal event in hominid evolution that determined the emergence of language.…”

Section: Introductionmentioning

confidence: 99%

Hand and paw preferences in relation to the lateralized brain

Rogers

2008

Phil. Trans. R. Soc. B

192

167

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Hand preferences of primates are discussed as part of the broad perspective of brain lateralization in animals, and compared with paw preferences in non-primates. Previously, it has been suggested that primates are more likely to express a species-typical hand preference on complex tasks, especially in the case of coordinated hand use in using tools. I suggest that population-level hand preferences are manifested when the task demands the obligate use of the processing specialization of one hemisphere, and that this depends on the nature of the task rather than its complexity per se. Depending on the species, simple reaching tasks may not demand the obligate use of a specialized hemisphere and so do not constrain limb/hand use. In such cases, individuals may show hand preferences that are associated with consistent differences in behaviour. The individual's hand preference is associated with the expression of behaviour controlled by the hemisphere contralateral to the preferred hand (fear and reactivity in left-handed individuals versus proactivity in right-handed individuals). Recent findings of differences in brain structure between left-and right-handed primates (e.g. somatosensory cortex in marmosets) have been discussed and related to potential evolutionary advances.

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Cerebral Asymmetry and Human Uniqueness

Cited by 7 publications

References 89 publications

Brain Size Associated with Foot Preferences in Australian Parrots

Brain Size Associated with Foot Preferences in Australian Parrots

Neuropil distribution in the cerebral cortex differs between humans and chimpanzees

Hand and paw preferences in relation to the lateralized brain

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