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

/pdf/an-integrative-theory-of-prefrontal-cortex-function-2j9unprn5f.pdf

An integrative theory of prefrontal cortex function

Publisher Summary This chapter focuses on the modern notion of short-term memory, called working memory. Working memory refers to the temporary maintenance of information that was just experienced or just retrieved from long-term memory but no longer exists in the external environment. These internal representations are short-lived, but can be maintained for longer periods of time through active rehearsal strategies, and can be subjected to various operations that manipulate the information in such a way that makes it useful for goal-directed behavior. Working memory is a system that is critically important in cognition and seems necessary in the course of performing many other cognitive functions, such as reasoning, language comprehension, planning, and spatial processing. This chapter demonstrates the functional importance of dopamine to working memory function in several ways. Elucidation of the cognitive and neural mechanisms underlying human working memory is an important focus of cognitive neuroscience and neurology for much of the past decade. One conclusion that arises from research is that working memory, a faculty that enables temporary storage and manipulation of information in the service of behavioral goals, can be viewed as neither a unitary, nor a dedicated system. Data from numerous neuropsychological and neurophysiological studies in animals and humans demonstrates that a network of brain regions, including the prefrontal cortex, is critical for the active maintenance of internal representations.

Chapter 11 Working memory

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

Attention and Effort

We describe the memory functioning of C, a professional musician who became amnesic following herpes simplex encephalitis in 1985. Although transient amnesia in a professional musician has previously been described, this is the first reported case of chronic amnesia in a highly talented professional musician. C is unusual in three respects. First, his amnesia is particularly severe. Second, his amnesia includes semantic as well as episodic memory deficits. Third, he believes he has just woken up and his preoccupation with this state of 'just wakening' has persisted for over 9 years. This appears to be the result of a delusion rather than the consequence of his amnesia.

Dense amnesia in a professional musician following herpes simplex virus encephalitis.

Individuals with Down syndrome are thought to perform poorly on tests of verbal short-term memory, such as measures of word span or digit span. This review critically examines the evidence for a specific deficit in verbal short-term memory in Down syndrome, and outlines a range of possible explanations for such a deficit. The potential implications of a verbal short-term memory impairment for broader aspects of development are outlined, in particular with respect to vocabulary development. Possible intervention strategies, which might improve verbal short-term memory performance in Down syndrome are also considered. However, we argue that further research is needed to fully clarify the nature of a verbal short-term memory deficit in Down syndrome, before the merits of these various intervention approaches can be properly evaluated.

/pdf/down-syndrome-and-the-phonological-loop-the-evidence-for-and-3ujx45o06t.pdf

Down syndrome and the phonological loop: the evidence for, and importance of, a specific verbal short-term memory deficit.

Becker (1988) has argued that Alzheimer's disease is particularly characterised by a combination of amnesic and dysexecutive deficits He has supported this hypothesis by identifying patients who represent a relatively pure example of each of these We describe a search for similarly pure patients in a sample of 55 carefully selected Alzheimer cases We succeed in identifying one case each of relatively pure amnesia and relatively pure dysexecutive syndrome We also, however, find cases of predominant STM deficit, as well as cases with defective visual but not verbal memory, and cases of the converse pattern These cases do not seem to reflect simple random variation in the data, since less theoretically coherent patterns of symptoms are not found in this pure form We conclude that AD can give rise to relatively specific cognitive deficits during its early stages, but that these do not necessarily argue for Becker's two-component interpretation of the cognitive deficit in Alzheimer's disease

The two-component hypothesis of memory deficit in Alzheimer's disease

We examine the role of general attention in the binding of colour and shape across the visual and verbal modalities. Three experiments studied the effects of concurrent tasks on the binding and retention of either unified visual stimuli, namely coloured shapes, or cross-modal stimuli in which one feature involved visual and the other auditory presentation. Performance accuracy was broadly equivalent across conditions, and was unimpaired by spatial tapping but impaired by backward counting. The decrement was however, no greater for the cross-modal binding conditions, suggesting that the act of binding is not itself attention demanding. Implications for this unexpected finding are discussed.

Alan D. Baddeley

Papers

Dense amnesia in a professional musician following herpes simplex virus encephalitis.

Down syndrome and the phonological loop: the evidence for, and importance of, a specific verbal short-term memory deficit.

The two-component hypothesis of memory deficit in Alzheimer's disease

Cross-modal binding and working memory

The children's test of non-word repetition