The functional architecture of the left posterior and lateral prefrontal cortex in humans

The anatomical and functional organization of the lateral prefrontal cortex (LPFC) is one of the most debated issues in cognitive and integrative neurosciences. The aim of this study is to determine whether the human LPFC is organized according to the domain of information, to the level of the processing or to both of these dimensions. In order to clarify this issue, we have designed an experimental protocol that combines a functional magnetic resonance imaging study in healthy subjects (n = 12) and a voxel-by-voxel lesion mapping study in patients with focal prefrontal lesions (n = 37) compared with normal controls (n = 48). Each method used the same original cognitive paradigm (the domain n-back tasks) that tests by a cross-dimensional method the domain of information (verbal, spatial, faces) and the level of processing (from 1- to 3-back). Converging data from the 2 methods demonstrate that the left posterior LPFC is critical for the higher levels of cognitive control and is organized into functionally different subregions (Brodman's area 9/46, 6/8/9, and 44/45). These findings argue in favor of a hybrid model of organization of the left posterior LPFC in which domain-oriented (nonspatial and spatially oriented) and cross-domain executive-dependent regions coexist, reconciling previously divergent data.