Structure and Functions of the Human Prefrontal Cortex

Cerebral Cortex, 2008

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 5 12) and a voxel-by-voxel lesion mapping study in patients with focal prefrontal lesions (n 5 37) compared with normal controls (n 5 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. Figure 1. Experimental tasks. (a) Schematic representation of the verbal, figurative (faces) and spatial n-back tasks performed by patients and controls in the lesion study. (b) Temporal organization of a run of the n-back tasks performed by subjects in the fMRI study.

The purpose of this study was to compare the validity of two models which contrast with each other in the manner in which they integrate neuropsychological tests into distinct prefrontal constructs. The first prefrontal model consists of five distinct functional constructs drawn from human clinical neuropsychology. The second model, elaborated by Goldman-Rakic, is based primarily on monkey re­ search and postulates a basic prefrontal function, "on-line representational mem­ ory," which guides behavior in the absence of, or despite discriminative environ­ mental stimuli. In the latter model, distinct prefrontal functional constructs are primarily defined in terms of various types of representational memory involved in specific tasks. Eleven "prefrontal" measures were obtained from 259 normal adults, stratified for age, education, and sex. Confirmatory factor analyses revealed that the Goldman-Rakic model "fit" the data better than the model derived from human clinical neuropsychology, while several constructs commonly used in human neuropsychology were refuted. It was concluded that new research on brain­ damaged humans with a view to understanding prefrontal function might benefit from using the Goldman-Rakic model as a starting point.

Annals of the New York Academy of Sciences, 1995

2001

The prefrontal cortex has long been suspected to play an important role in cognitive control, in the ability to orchestrate thought and action in accordance with internal goals. Its neural basis, however, has remained a mystery. Here, we propose that cognitive control stems from the active maintenance of patterns of activity in the prefrontal cortex that represent goals and the means to achieve them. They provide bias signals to other brain structures whose net effect is to guide the flow of activity along neural pathways that establish the proper mappings between inputs, internal states, and outputs needed to perform a given task. We review neurophysiological, neurobiological, neuroimaging, and computational studies that support this theory and discuss its implications as well as further issues to be addressed.

Cerebral Cortex, 2007

Philosophical Transactions of the Royal Society of London. Series B: Biological Sciences, 2002

The ability to generalize behaviour–guiding principles and concepts from experience is key to intelligent, goal–directed behaviour. It allows us to deal efficiently with a complex world and to adapt readily to novel situations. We review evidence that the prefrontal cortex—the cortical area that reaches its greatest elaboration in primates—plays a central part in acquiring and representing this information. The prefrontal cortex receives highly processed information from all major forebrain systems, and neurophysiological studies suggest that it synthesizes this into representations of learned task contingencies, concepts and task rules. In short, the prefrontal cortex seems to underlie our internal representations of the ‘rules of the game’. This may provide the necessary foundation for the complex behaviour of primates, in whom this structure is most elaborate.

Luria's Legacy in the 21st Century, 2009

Here, we briefly present a model based on our recent brain imaging results describing the functional organization of the lateral prefrontal cortex underlying cognitive control (3). According to our model and in agreement with empirical data (4,5), cognitive control is subserved by a system of lateral prefrontal regions forming a cascade of top-down selection processes operating along the caudo-rostral axis from the premotor cortex to the most anterior region of the frontal lobes, the so-called frontopolar cortex. In this system, the premotor cortex is involved in selecting actions in response to stimuli (sensorimotor control), while posterior lateral prefrontal regions are involved in selecting premotor representations (stimulus-response associations) according to the immediate context of action, i.e. with respect to contextual signals accompanying stimulus occurrences (contextual control). More anterior prefrontal regions, in turn, are involved in selecting posterior prefrontal rep...

2012

Journal homepage: www.elsevier.com/locate/cortex c o r t e x 4 8 ( 2 0 1 2 ) 4 6 e5 7 0010-9452/$ e see front matter ª

HT 85a.1 (precedes *638 VIR); HT 86a.4 (second heading); HT 88.1 (precedes VIR+KA); HT 95b.1 (heading to second list of same names); HT 99a.1: HT 133.1-2 (precedes TE GRA+DA); ZA Wc.a1-2 (edges: KZ 209)