This recent expansion of human parietal cortex emerges when comparing the endocasts of archaic Western European Neanderthals to those of modern Homo who, although belonging to different evolutionary lines, share the same cranial capacity and overall brain dimensions. This occurrence favours the identification of specific departures from the Homo allometric trajectory during the evolution CDK assay of Homo sapiens, made apparent by the method of subtraction (Gould, 1966). For example, multivariate morphometrics and geometrical
modelling (Bruner et al., 2003; Bruner, 2008) indicate that modern human endocasts show a significant midsagittal enlargement of the parietofrontal outline, which is more pronounced at the level of parietal cortex, and a dorsovertical lengthening of the parietocerebellar volumes. We interpret this result as reflecting an enlargement of the entire distributed system of which parietal cortex is a crucial node, and which probably also includes the parietocerebellar pathway through the pontine nuclei. Additional insight into the evolution of human parietal cortex can be gained by comparing the deficits of parietal lesions in monkeys and humans.
Generally speaking, some basic features of the parietal lobe syndrome in humans can also be found in monkeys, especially when considering optic ataxia. However, experimental evidence showing that directional hypokinesia can be reproduced in monkeys after unilateral cortical lesions is controversial. In fact, testing for directional BI6727 hypokinesia in animal models has proven to be problematic because the over-training required to get monkeys to perform the visuomotor tasks necessary SB-3CT to measure directional hypokinesia can lead to an important mitigation of the lesion effects, especially when measured by some forms of testing. Therefore, in monkey studies the definition that has been generally adopted for indicating the presence of neglect can be summarize as follows: ‘Diminished
responses to sensory stimulation and disuse of limbs in half of personal and extrapersonal space under certain conditions or testing with preservation of primary sensory and motor response on that side’ (Deuel, 1987). According to this view, lesions of different cortical areas, including IPL (Heilman et al., 1970; Deuel & Farrar, 1993), area PE and PFG in marmoset monkeys (Marshall et al., 2002), superior temporal cortex (Luh et al., 1986; Watson et al., 1994) and premotor cortex (Rizzolatti et al., 1983) lead to behavioural deficits that overall have been interpreted as a form of neglect. Furthermore, the lack of quantitative analyses of most lesion studies in monkeys does not allow any conclusive statement on neglect.