The unity and diversity of executive functions and their contributions to complex "Frontal Lobe" tasks: a latent variable analysis.

▪ Abstract 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

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An integrative theory of prefrontal cortex function

Co-Planar Stereotaxic Atlas of the Human Brain—3-Dimensional Proportional System: An Approach to Cerebral Imaging, J. Talairach, P. Tournoux. Georg Thieme Verlag, New York (1988), 122 pp., 130 figs. DM 268

An automated method for neuroanatomic and cytoarchitectonic atlas-based interrogation of fMRI data sets

The concept of working memory proposes that a dedicated system maintains and stores information in the short term, and that this system underlies human thought processes. Current views of working memory involve a central executive and two storage systems: the phonological loop and the visuospatial sketchpad. Although this basic model was first proposed 30 years ago, it has continued to develop and to stimulate research and debate. The model and the most recent results are reviewed in this article.

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Working memory: looking back and looking forward

Assessments are carried out in order to answer questions. Consequently, the
nature of the question determines the assessment procedure. So we would use
different tests and procedures for testing out a theoretical model than we would
for trying to predict the likelihood of successful return to work for a brain-injured
patient. An example of the former is the work of Baddeley, Logie, Bressi, Della
Sala, and Spinnler (1986), who were trying to support or refute their hypothesis
that patients with Alzheimer’s disease had a deficit in the central executive
component of the working memory model (Baddeley & Hitch, 1974). An
example of the latter is Shallice and Burgess’s (1991) six elements test which
requires participants to plan and organise their activity over a 15-minute period
while following certain rules. Mayes (1986) discusses the different concerns of
researchers and clinicians with regard to memory assessments but his views are
equally relevant to assessments of executive functioning. When thinking about
frontal lobe or executive functioning clinicians are likely to be concerned with
answering such questions as:1. Does this person have cognitive impairments that are typically associated
with the Dysexecutive syndrome (DES)?

Behavioural Assessment of the Dysexecutive Syndrome

This article presents findings from the Children's Test of Nonword Repetition (CNRep). Normative data based on its administration to over 600 children aged between four and nine years are reported. Close developmental links are established between CNRep scores and vocabulary, reading, and comprehensive skills in children during the early school years. The links between nonword repetition and language skills are shown to be consistently higher and more specific than those obtained between language skills and another simple verbal task with a significant phonological memory component, auditory digit span. The psychological mechanisms underpinning these distinctive developmental relationships between nonword repetition and language development are considered.

The children's test of nonword repetition: A test of phonological working memory

Ninety-two mixed etiology neurological patients and 216 control participants were assessed on a range of neuropsychological tests, including 10 neuropsychological measures of executive function derived from 6 different tests. People who knew the patients well (relatives or carers) completed a questionnaire about the patient's dysexecutive problems in everyday life, and this paper reports the extent to which the tests predicted the patients' everyday life problems. All of the tests were significantly predictive of at least some of the behavioral and cognitive deficits reported by patients' carers. However, factor analysis of the patients' dysexecutive symptoms suggested a fractionation of the dysexecutive syndrome, with neuropsychological tests loading differentially on 3 underlying cognitive factors (Inhibition, Intentionality, and Executive Memory), supporting the conclusions that different tests measure different cognitive processes, and that there may be limits to the fractionation of the executive system.

/pdf/the-ecological-validity-of-tests-of-executive-function-28ge0r94je.pdf

The ecological validity of tests of executive function.

Universal positive correlations between different cognitive tests motivate the concept of "general intelligence" or Spearman's g. Here the neural basis for g is investigated by means of positron emission tomography. Spatial, verbal, and perceptuo-motor tasks with high-g involvement are compared with matched low-g control tasks. In contrast to the common view that g reflects a broad sample of major cognitive functions, high-g tasks do not show diffuse recruitment of multiple brain regions. Instead they are associated with selective recruitment of lateral frontal cortex in one or both hemispheres. Despite very different task content in the three high-g-low-g contrasts, lateral frontal recruitment is markedly similar in each case. Many previous experiments have shown these same frontal regions to be recruited by a broad range of different cognitive demands. The results suggest that "general intelligence" derives from a specific frontal system important in the control of diverse forms of behavior.

/pdf/a-neural-basis-for-general-intelligence-yoytwigoge.pdf

Hazel Emslie

Papers

Behavioural Assessment of the Dysexecutive Syndrome

The children's test of nonword repetition: A test of phonological working memory

The ecological validity of tests of executive function.

A Neural Basis for General Intelligence

Intelligence and the frontal lobe: the organization of goal-directed behavior.