The counting function and its representation in the parietal cortex in humans and animals.

Current data provide evidence that the ability to assess numbers is present not only in adult humans, but also in animals and children of preverbal age. Studies of behavior in infants and animals have demonstrated that the perception of number, the discrimination of quantities, and elementary addition and subtraction appear during onto- and phylogenesis before the appearance of speech. Number perception in humans and animals has common features: the greater the difference between numbers, the easier they are to discriminate; for a given difference between numbers, increases in size lead to increased difficulty in discrimination. Clinical data on counting impairments in patients and functional tomography studies of number operations in healthy subjects have shown that the key structures involved in number perception in humans are located in the parietal cortex. As demonstrated by experiments on monkeys and dogs, recognition of number in these species is also associated with the parietal area of the cortex. The similarity of the morphofunctional bases of "counting behavior" in humans and animals suggests that counting can be regarded as a functional mechanism of adaptive behavior which formed during evolution.

[Computing function and its representation in the parietal cortex in humans and animals].

The currently available evidence suggests that not only adults but children of preverbal age and animals possess the ability to define numbers. The behavioral studies in infants and animals show that number perception, quantity discrimination, and elementary adding and subtraction appear in onto- and phylogenesis prior to language. There are parallels between number processing in animals and humans: a) the ability to discriminate between two numbers improves as the numerical distance between them increases; b) for equal numerical distance, discrimination of two numbers worsens as their numerical size increases. Disorders of "number sense" in brain-lesioned patients and brain-imaging of number processing in healthy subjects showed that the parietal cortex includes the key structures involved in number perception. These structures include the intraparietal sulcus area, angular gyrus and superior lobule. Animal experiments showed that the parietal cortex is also important for "counting behavior" in monkeys (area of the intraparietal sulcus and area 5), dogs (area 5) and cats (area 7). Parallels between functional and morphological bases of number perception in humans and animals suggest that they endow it in evolution as the usual fundamental mechanism of adaptive behavior.