Human Brain

Read here about a human body organ and its role in issues of scale.

Brain Regions In Numerosity

Nunez summarizes the evidence linking these abilities to regions of the brain. Three areas are implicated: the basal ganglia for rote comprehension; the inferior parietal cortex for basic arithmetic, being the comprehension of number and numeral; and other areas for algebraic calculation.

intraparietal sulcus

Dahaene summarized in Annual Review of Neuroscience 2009:
Case studies of the pathology of numerical competence historically provided the first insights into its neural foundation. Acquired calculation deficits (acalculia) occurred after brain damage near the parieto-occipito-temporal junction (Henschen 1919, Gerstmann 1940) or in the frontal lobe (Luria 1966). The first functional imaging studies of mental arithmetic quickly pointed to a reproducible bilateral parietal and prefrontal activation (Appolonio et al. 1994, Dehaene et al. 1996, Roland & Friberg 1985). More specifically, the banks of the intraparietal sulcus (IPS) are consistently activated whenever adults compute simple comparison, addition, subtraction, or multiplication with Arabic numerals (Chochon et al. 1999, Pinel et al. 2001).The IPS is activated even when they merely detect a digit among colors and letters (Eger et al. 2003). The intraparietal region seems to be associated with an abstract, amodal representation of numbers inasmuch as it can be activated by numbers presented in various culturally learned symbolic notations such as Arabic numerals and spelled-out or spoken number words (Eger et al. 2003), even across various countries and cultures including France, the United Kingdom, the United States, Austria, Singapore, China, and Japan (Tang et al. 2006).

Inferior Parietal Cortex

Ten cases of patients with Epilepsia arithmetices indicate that the inferior parietal cortex is involved in symbolic numerical abilities. Neural connections from vision, audition, and touch come together in this highly associative area. Dehaene argues that its capabilities are implicated since
  • Numbers are connected to fingers because children learn to count on their fingers.
  • Numbers are related to writing because they are symbolized by written numerals.
  • Numbers are related to space in various ways; subitizing, for example, requires objects to be distributed over space, and integers are conceptualized as being spread in space over a number line.
  • Mathematical talent often correlates with spatial abilities.

Cartoon of human brain, from Nunez and Lakoff 2000.

Basal ganglia

Some number manipulation is by rote, such as the multiplication tables, or knowing the value of Pi. Rote abilities seem to be subcortical, associated with the basal ganglia.

Other Brain Areas

Other brain areas are implicated for algebraic calculation. Rare cases of acalculia, the inability to do basic arithmetic, prove this, such as the chemist who cannot solve 2 • 3, 7 – 3, 9 ÷ 3, or 5 • 4, yet can simplify (a • b) / (b • a) into 1 and a • a • a into a^3. Dehaene concludes that algebraic calculation and arithmetic calculation are processed in different brain regions, but does not report the region (Nunez p.26).

William Sarter has delineated a neuronal model of “attentional effort ” that describes the mechanisms for initiation of top – down control of attention. When attention is threatened, performance monitoring (prefrontal – anterior cingulate) and motivational (mesolimbic) systems are recruited and integrated, manifesting as attentional effort. (Bruya p.5)

Links and References

Click below to read about other organs and their role in scale studies: