Brain maps, great and small: lessons from comparative studies of primate visual cortical organization

Abstract

In this paper, we review evidence from comparative studies of primate cortical organization, highlighting recent findings and hypotheses that may help us to understand the rules governing evolutionary changes of the cortical map and the process of formation of areas during development. We argue that clear unequivocal views of cortical areas and their homologies are more likely to emerge for "core" fields, including the primary sensory areas, which are specified early in development by precise molecular identification steps. In primates, the middle temporal area is probably one of these primordial cortical fields. Areas that form at progressively later stages of development correspond to progressively more recent evolutionary events, their development being less firmly anchored in molecular specification. The certainty with which areal boundaries can be delimited, and likely homologies can be assigned, becomes increasingly blurred in parallel with this evolutionary/developmental sequence. For example, while current concepts for the definition of cortical areas have been vindicated in allowing a clarification of the organization of the New World monkey "third tier" visual cortex (the third and dorsomedial areas, V3 and DM), our analyses suggest that more flexible mapping criteria may be needed to unravel the organization of higher-order visual association and polysensory areas.

Differences in genetic and environmental influences on the human cerebral cortex associated with development during childhood and adolescence

“…Characteristics of specific cortical areas develop over time in response to the local combination of growth factors and activation. It has been argued that primary motor and sensory cortices may serve as core anchor regions, which develop early in ontogeny through clear, strongly genetically-mediated steps [Rosa and Tweedale, 2005]. The pattern observed here of genetic effects predominating in these core regions early in childhood may be consistent with their relatively early development.…”

Comparative Anatomy of Marmoset and Mouse Cortex from Genomic Expression

“…Our finding of common gene expression in V1 and MT suggests that MT functions as a "primary" visual area, supporting the idea of duplicating and adding new areas to older modules (Fig. 5) (Rosa and Tweedale, 2005). To support this idea, it is shown that the difference in development and organization between areas 17 and 18 in Old World primates derives from the cell fate decision that originated already in the proliferative ventricular zone before neurons began to migrate to their areal and laminar positions (Kornack and Rakic, 1998).…”

“…The marmoset has a number of advantageous characteristics as an experimental animal, including a small body size, high fertility, and early sexual maturity (they reach adulthood at 1.5-2 years). The marmoset cortex is relatively smooth, but the gyrencephalic and cortical sheet is divided into functionally distinct cortical areas, as in Old World monkeys (Rosa and Tweedale, 2005) and is routinely used in studies of higher cognitive functions and social communication (Bonnin et al, 2007;Eliades and Wang, 2008). Therefore, marmosets are considered to be a good experimental model animal to understand the evolution of brain development and function.…”

The role of long-range connections on the specificity of the macaque interareal cortical network

“…Considerable progress has been made in describing the functional regionalization of the cortex and the pathways linking cortical areas (2,3). This progress has led to an understanding that the organization of interareal connections constrains the flow of information through the cortex.…”