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

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

The memory performance of patients suffering from senile dementia of the Alzheimer type (SDAT) (N = 29), normal subjects of equivalent age and education (N = 58), and young normal controls (N = 42) was tested using free recall and verbal and nonverbal span. Three measures were derived from the free recall task: primacy based on the first item, secondary memory based on the middle serial positions, and primary memory based on recency and the Waugh-Norman correction factor. The SDAT patients differed from the normal elderly on all free recall and span measures except for primary memory. The elderly were clearly inferior to the young on secondary memory, and were marginally poorer on primary memory and the two span measures. Three possible explanations of this pattern of results are considered, based on the dichotomous modal model of memory, levels of processing, and working memory. It is suggested that the assumption that SDAT patients suffer from a deficit in the central executive component of wor...

Dementia, ageing, and the structure of human memory.

This chapter suggests that the existence of an episodic memory of that experience allows the organism to reflect on the experience, and act accordingly; The understanding of consciousness is clearly a fascinating and difficult question, and the proposal that it is somehow linked to working memory goes back at least to the modal model of Atkinson and Shiffrin The increase in flexibility granted by such a memory mechanism gives it considerable potential advantages over a simpler learning mechanism that produces a more automatic response The classic amnesic syndrome is typically associated with damage to the temporal lobes and/or hippocampus and limbic system A system such as working memory could be extremely useful in such an enterprise, and it seems likely that laboratory-based tasks like mental rotation are ways of measuring the manipulative capacities of working memory, in this case the visuo-spatial sketchpad

Working memory and conscious awareness.

A series of experiments explored the role of subvocalisation in fluent reading. Experiment I showed that when subjects were required to suppress articulation while reading, their ability to detect anomalous words or errors of word order in prose was markedly impaired although speed of reading was unaffected. Experiment II showed that this decrement was not a general effect due to performing a secondary task, since a concurrent tapping task did not impair detection accuracy. A third study explored the role of acoustic interference in reading by requiring subjects to detect errors in prose while attempting to ignore irrelevant speech, with or without articulatory suppression. Once again articulatory suppression led to a clear decrement in the subject's ability to detect errors, while unattended speech had no effect on performance. None of the manipulations influenced the speed with which the subjects performed the reading task. It is concluded that subvocalisation allows the creation of a supplementary arti...

The Role of Subvocalisation in Reading

A brief account is given of the evolution of the concept of working memory from a unitary store into a multicomponent system. Four components are distinguished, the phonological loop which is responsible for maintaining speech-based information, the visuospatial sketchpad performing a similar function for visual information, the central executive which acts as an attentional control system, and finally a new component, the episodic buffer. The buffer comprises a temporary multidimensional store which is assumed to form an interface between the various subsystems of working memory, long-term memory, and perception. The operation of the model is then illustrated through an account of a research programme concerned with the analysis of working memory in Down syndrome.

Working Memory and Down Syndrome.

This paper is divided into three sections The first reviews the evidence for a verbal short-term memory deficit in Down syndrome Existing research suggests that short-term memory for verbal information tends to be impaired in Down syndrome, in contrast to short-term memory for visual and spatial material In addition, problems of hearing or speech do not appear to be a major cause of difficulties on tests of verbal short-term memory This suggests that Down syndrome is associated with a specific memory problem, which we link to a potential deficit in the functioning of the 'phonological loop' of Baddeley's (1986) model of working memory The second section considers the implications of a phonological loop problem Because a reasonable amount is known about the normal functioning of the phonological loop, and of its role in language acquisition in typical development, we can make firm predictions as to the likely nature of the short-term memory problem in Down syndrome, and its consequences for language learning However, we note that the existing evidence from studies with individuals with Down syndrome does not fit well with these predictions This leads to the third section of the paper, in which we consider key questions to be addressed in future research We suggest that there are two questions to be answered, which follow directly from the contradictory results outlined in the previous section These are 'What is the precise nature of the verbal short-term memory deficit in Down syndrome?', and 'What are the consequences of this deficit for learning?' We discuss ways in which these questions might be addressed in future work

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Alan D. Baddeley

Papers

Dementia, ageing, and the structure of human memory.

Working memory and conscious awareness.

The Role of Subvocalisation in Reading

Working Memory and Down Syndrome.

Short-term memory in Down syndrome: applying the working memory model.