Architecture and Connections of Cortical Association Areas

The execution of behavior depends on the integration of activity at various levels of the central nervous system. Nevertheless, different regions of the nervous system have been shown to participate in specific functions. Whereas, at the cortical level, the primary and secondary sensory areas are involved in the elementary analysis of incoming information, the other regions of the cerebral cortex contribute to a variety of complex processes (Figs. 1 and 2). These latter regions are designated as association areas and may be conceptualized as being interposed between the external and the internal environments (Figs. 1 and 3). These areas are highly developed in primates and have been subdivided on the basis of architecture, their cortical and subcortical connections, and function, into several different types. For example, cortical areas subjacent to the primary sensory regions are termed first-order parasensory areas (Fig. 3), while those beyond the first-order parasensory areas are designated as second-order or third-order association areas (Jones and Powell, 1970a; Chavis and Pandya, 1976). Other cortical regions, which are situated at the junctions of modality-specificregions in parietal, occipital, and temporal cortices (Fig. 4), are termed multi-modal areas (Jones and Powell, 1970a; Seltzer and Pandya, 1976, 1978, 1980). Within the frontal lobe, beyond the motor cortex, a similar categorization of association areas has been identified (Jones and Powell, 1970a; Chavis and Pandya, 1976). Finally, the medial and ventral portions of the cerebral cortex contain groups of specialized regions (Fig. 5) which are termed paralimbic regions (Locke et al., 1964; Yakovlev et al., 1966; Pandya and Seltzer, 1982b).