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

Today's Web-enabled deluge of electronic data calls for automated methods of data analysis. Machine learning provides these, developing methods that can automatically detect patterns in data and then use the uncovered patterns to predict future data. This textbook offers a comprehensive and self-contained introduction to the field of machine learning, based on a unified, probabilistic approach. The coverage combines breadth and depth, offering necessary background material on such topics as probability, optimization, and linear algebra as well as discussion of recent developments in the field, including conditional random fields, L1 regularization, and deep learning. The book is written in an informal, accessible style, complete with pseudo-code for the most important algorithms. All topics are copiously illustrated with color images and worked examples drawn from such application domains as biology, text processing, computer vision, and robotics. Rather than providing a cookbook of different heuristic methods, the book stresses a principled model-based approach, often using the language of graphical models to specify models in a concise and intuitive way. Almost all the models described have been implemented in a MATLAB software package--PMTK (probabilistic modeling toolkit)--that is freely available online. The book is suitable for upper-level undergraduates with an introductory-level college math background and beginning graduate students.

Machine Learning : A Probabilistic Perspective

Background and Purpose—The authors present an overview of the current evidence and management recommendations for evaluation and treatment of adults with acute ischemic stroke. The intended audienc...

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Guidelines for the Early Management of Patients With Acute Ischemic Stroke A Guideline for Healthcare Professionals From the American Heart Association/American Stroke Association

I have developed "tennis elbow" from lugging this book around the past four weeks, but it is worth the pain, the effort, and the aspirin. It is also worth the (relatively speaking) bargain price. Including appendixes, this book contains 894 pages of text. The entire panorama of the neural sciences is surveyed and examined, and it is comprehensive in its scope, from genomes to social behaviors. The editors explicitly state that the book is designed as "an introductory text for students of biology, behavior, and medicine," but it is hard to imagine any audience, interested in any fragment of neuroscience at any level of sophistication, that would not enjoy this book. The editors have done a masterful job of weaving together the biologic, the behavioral, and the clinical sciences into a single tapestry in which everyone from the molecular biologist to the practicing psychiatrist can find and appreciate his or

Principles of Neural Science

Several problems in understanding executive functions and their relationships to the frontal lobes are discussed. Data are then presented from several of our studies to support the following statements: (1) the examination of patients with focal frontal lobe lesions is a necessary first step in defining the relation of executive functions to the frontal lobes; (2) there is no unitary executive function. Rather, distinct processes related to the frontal lobes can be differentiated which converge on a general concept of control functions; (3) a simple control-automatic distinction is inadequate to explain the complexity of control-automatic processes; (4) the distinction between complex and simple tasks cannot explain the differences in functions between the frontal lobes and other brain regions; and (5) the most important role of the frontal lobes may be for affective responsiveness, social and personality development, and self-awareness and unconsciousness.

Executive functions and the frontal lobes: a conceptual view

Mild traumatic brain injury (TBI) is one of the most common neurologic disorders, with only migraine and herpes zoster having higher incidences and only migraine having a higher preva1ence.l Most patients with mild TBI recover within weeks to months without specific intervention, but at 1 year after injury approximately 15% of patients still have disabling symptom^.^^^ The incidence of mild TBI patients who will be persistently symptomatic is approximately 27/100,000, estimated as 15% of 180/100,000 mild TBI incidence.l This is equal to the annual incidence of Parkinson’s disease (20/100,000), multiple sclerosis (3/100,000), Guillain-Barre syndrome (2/100,000), motor neuron disease (2/100,000), and myasthenia gravis (0.4/100,000) combinedl (27.4/100,000). The modal persistently symptomatic patient is a man in his 20s or 30s. Only myasthenia gravis has a similar preponderance of young patients. Since mild TBI does not affect life expectancy, this generally young cohort potentially faces decades of disability. Postgraduate teaching in neurology does not mirror the high prevalence of this disorder-ie, most residents probably do not get proportionate instruction in the diagnosis and management of mild TBI. There are many reasons for this apparent failure to consider such a common disorder. First, treatment of the acute phase is not usually provided by neurologists but rather by neurosurgeons, emergency room physicians, and primary care physicians. Second, most patients get better on their own. Third, the persistently symptomatic patients are often viewed-sometimes correctly-as unpleasant clinical assignments; litigation, compensation, and suspicion of malingering (or at least exaggerating) often accompany them. Fourth, there are frequently vaguely specified psychological issues that seem to-and often do-impede straightforward treatment. Fifth, the disorder is not intellectually compelling when compared with drug management of complex Parkinson’s disease, plasmapheresis, or modern treatment of multiple sclerosis. Sixth, there is no academic reward from these patients; review of the three major American neurology journals from 1990 to 1992 revealed only one article4 on mild TBI, and that article described the effect of mild TBI on the natural history of Parkinson’s disease. The clinical phenomenology of mild TBI follows coherently from the neuropathology. The clinical deficits caused by the neurologic injury can be understood as manifestations of impaired attention. The natural course of recovery can be anticipated. The associated injuries that contribute symptoms to the clinical picture have reasonably specific treatments. The risk factors for developing persistent symptoms can be recognized. Recognition and appropriate management of the risk factors may block development of chronic disability. This review will provide a framework for clinical management of the patient with mild TBI.

Mild traumatic brain injury: pathophysiology, natural history, and clinical management.

Patients with limited focal frontal and nonfrontal lesions were tested for visual perspective taking and detecting deception. Frontal lobe lesions impaired the ability to infer mental states in others, with dissociation of performance within the frontal lobes. Lesions throughout the frontal lobe, with some suggestion of a more important role for the right frontal lobe, were associated with impaired visual perspective taking. Medial frontal lesions, particularly right ventral, impaired detection of deception. The former may require cognitive processes of the lateral and superior medial frontal regions, the latter affective connections of the ventral medial frontal with amygdala and other limbic regions.

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Michael P. Alexander

Papers

Principles of Neural Science

Executive functions and the frontal lobes: a conceptual view

Mild traumatic brain injury: pathophysiology, natural history, and clinical management.

The frontal lobes are necessary for `theory of mind'

Clustering and switching on verbal fluency: the effects of focal frontal- and temporal-lobe lesions