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Association Cortex Size

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Human Uniqueness Compared to "Great Apes": 
Absolute Difference
MOCA Domain: 
Neuroscience
MOCA Topic Authors: 
Todd M Preuss

The classical association cortical regions are larger in absolute terms in humans than in other primates,

and also larger relative to primary sensorimotor regions. In humans and in apes, the lower-order sensorimotor areas of the cortex are about the same absolute size (in surface area and volume). Human brains are much larger than those of apes, and the difference reflects the much greater absolute and relative size of the "association" cortex, including the classical prefrontal, posterior parietal, and temporal association regions.

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Referenced By:
TitleCertainty
Larger and More Numerous Von Economo (Spindle) CellsNone
Timing

Timing of Appearance of the Difference in the Hominin Lineage.

For this entry assume that

  • the common ancestor of humans and old world monkeys was 25000 thousand (25 million) years ago
  • the common ancestor of humans and chimpanzees was 6000 thousand (6 million) years ago
  • the emergence of the genus Homo was 2000 thousand (2 million) years ago
  • the common ancestor of modern humans was 100 thousand years ago

 

Possible Appearance: 
6000 Thousand Years
Definite Appearance: 
2000 Thousand Years
Background Information: 

 Data come primarily from the work of Brodmann (1912) and Blinkov and Glezer (1968).  See the recent summary in Preuss (2011).

The Human Difference: 

 Humans have much more association cortex, both in absolute amount and relative to the amount of primary sensory and motor cortex, than do apes or monkeys.

Implications for Understanding Modern Humans: 

 The association cortices provide the main neural substrate of the extreme cognitive and behavioral specializations of the human species.

References: 
  • Blinkov S, Glezer I (1968) The Human Brain in Figures and Tables. New York: Basic Books.
  • Brodmann K (1912) Neue Ergibnisse uber die vergleichende histologische Lokalisation der Grosshirnrinde mit besonderer Berucksichtigung des Stirnhirns. Anat Anzeiger (Suppl) 41:157-216.
  • Preuss TM (2011) The human brain: rewired and running hot. Ann N Y Acad Sci 1225 Suppl 1:E182-191.www.ncbi.nlm.nih.gov/pubmed/21599696