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

Cognitive rehabilitation in clinical neuropsychology.

Primary objective: To describe the functional outcome of 19 patients with anterior communicating artery aneurysm following the completion of an inter-disciplinary out-patient rehabilitation programme.Research design: Retrospective descriptive study. Setting: Community-based inter-disciplinary outpatient programme. Patients: n = 19; consecutive referred sample, mean 182 days post-onset; in-patient rehabilitation completed. Intervention: Inter-disciplinary treatment of functional activities; 2–5 hours/day, 3–5 days/week; mean duration: 55–57 days.Main outcome measures: Supervision rating scale (SRS) and change in prevalence at admission and discharge of executive impairments, memory, confabulation, apathy, initiation, social inappropriateness and incontinence.Results: Sixty per cent of the patients showed a clinically significant improvement in their SRS from requiring full-time supervision to part-time supervision. Change in SRS was correlated with change in the impairments of executive function, memory an...

Outpatient rehabilitation of patients with chronic cognitive impairments after ruptured anterior communicating artery aneurysms reduces the burden of care: a pilot study.

We report the case of a 74-year-old woman (E.B.) who suffered the delusion that her husband had been psychologically replaced by her father (i.e., Capgras syndrome) after she had sustained a serious traumatic brain injury. Before her head injury, E.B. had severe amnesia of unknown etiology, which had been carefully documented over a 10-year period ; there was no evidence of delusional tendencies during this time. Subsequent to her head injury, E.B. displayed persistent misidentification of her husband's identity alongside impaired performance on tests of frontal/executive functions and increased difficulties on measures of remote memory. Longitudinal analyses revealed that E.B.'s delusion resolved in tandem with improved performance on tests of frontal network functions. There was no accompanying change in the status of her amnesia. E.B.'s executive deficits and delusions may have been independent manifestations of her brain injury, which cleared simultaneously. Alternatively, there may have been a causal relationship between these phenomena in that frontal/executive deficits may have been critically involved in the genesis of her delusions.

A neuropsychological analysis of Capgras syndrome

A 40-year-old man presented with a major nondominant hemisphere stroke syndrome after a road traffic accident. Cranial computed tomography scan revealed an extensive right hemisphere infarction involving the entire anterior and middle cerebral artery territories. Duplex Doppler ultrasound and cerebral angiography revealed bilateral internal carotid artery dissection with evidence of underlying fibromuscular dysplasia. Anticoagulation with heparin was commenced despite the coexisting large cerebral infarction, with the objective of protecting the uninjured but at-risk left cerebral hemisphere from ischemic injury. Patients with multiple cerebral arterial dissections complicated by cerebral infarction present a significant management dilemma. Our literature review revealed a lack of clear management guidelines for such cases.

Traumatic bilateral carotid dissection with concomitant cerebral infarction.

There are at least four categories of mental function that depend on structures in the frontal lobes: energization, executive capacity, self-regulation, and metacognition. Each is defined by specific anatomical localization and connectivity as well as by its unique mental processes. This diversity of structure and function cannot easily be reduced to just ‘executive’ function. These processes are flexibly assembled in response to context, complexity, and intention over real time into different networks within the frontal regions (and between frontal and posterior regions). In patients with focal lesions, there is no evidence for a generic frontal lobe, or dysexecutive, syndrome.

Michael P. Alexander

Papers

Cognitive rehabilitation in clinical neuropsychology.

Outpatient rehabilitation of patients with chronic cognitive impairments after ruptured anterior communicating artery aneurysms reduces the burden of care: a pilot study.

A neuropsychological analysis of Capgras syndrome

Traumatic bilateral carotid dissection with concomitant cerebral infarction.

Frontal Lobe Syndrome