This chapter contains sections titled: The Problem, The Generalized Delta Rule, Simulation Results, Some Further Generalizations, Conclusion

/pdf/learning-internal-representations-by-error-propagation-100fypr7vm.pdf

Learning internal representations by error propagation

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

We review evidence for partially segregated networks of brain areas that carry out different attentional functions. One system, which includes parts of the intraparietal cortex and superior frontal cortex, is involved in preparing and applying goal-directed (top-down) selection for stimuli and responses. This system is also modulated by the detection of stimuli. The other system, which includes the temporoparietal cortex and inferior frontal cortex, and is largely lateralized to the right hemisphere, is not involved in top-down selection. Instead, this system is specialized for the detection of behaviourally relevant stimuli, particularly when they are salient or unexpected. This ventral frontoparietal network works as a 'circuit breaker' for the dorsal system, directing attention to salient events. Both attentional systems interact during normal vision, and both are disrupted in unilateral spatial neglect.

Control of goal-directed and stimulus-driven attention in the brain

▪ 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

Much effort has been made to understand the role of attention in perception; much less effort has been placed on the role attention plays in the control of action Our goal in this chapter is to account for the role of attention in action, both when performance is automatic and when it is under deliberate conscious control We propose a theoretical framework structured around the notion of a set of active schemas, organized according to the particular action sequences of which they are a part, awaiting the appropriate set of conditions so that they can become selected to control action The analysis is therefore centered around actions, primarily external actions, but the same principles apply to internal actions—actions that involve only the cognitive processing mechanisms One major emphasis in the study of attentional processes is the distinction between controlled and automatic processing of perceptual inputs (eg, Shiffrin & Schneider, 1977) Our work here can be seen as complementary to the distinction between controlled and automatic processes: we examine action rather than perception; we emphasize the situations in which deliberate, conscious control of activity is desired rather than those that are automatic

Attention to action: willed and automatic control of behavior

An information-processing model is outlined that predicts that performance on non-routine tasks can be impaired independently of performance on routine tasks. The model is related to views on frontal lobe functions, particularly those of Luria. Two methods of obtaining more rigorous tests of the model are discussed. One makes use of ideas from artificial intelligence to derive a task heavily loaded on planning abilities. A group of patients with left anterior lesions has a specific deficit on the task. Subsidiary investigations support the inference that this is a planning impairment.

Specific impairments of planning

As a cognitive neuropsychologist, Tim Shallice considers the general question of what can be learned about the operation of the normal cognitive system from the study of the cognitive difficulties arising from neurological damage and disease. He distinguishes two types of theories of normal function - primarily modular and primary non-modular - and argues that the problems of making valid inferences about normal function from studies of brain-damaged subjects are more severe for the latter. He first analyzes five well-researched areas in which some modularity can be assumed: short-term memory, reading, writing, visual perception, and the relation between input and output language processing. His aim is to introduce the methods about normal function mirror ones derived directly from studies of normal subjects and indeed at times preceded them. He then more theoretically examines these inferences, from group studies and individual case studies to modular and non-modular systems. Finally, he considers five areas where theories of normal function are relatively undeveloped and neuropsychology provides counterintuitive phenomena and guides to theory-building: the organization of semantic systems, visual attention, concentration and will, episodic memory, and consciousness.

From Neuropsychology to Mental Structure

Attention to Action: Willed and Automatic Control of Behavior Technical Report No. 8006.

A quantitative investigation of the ability to carry out a variety of cognitive tasks was performed in 3 patients who had sustained traumatic injuries which involved prefrontal structures. All 3 had severe difficulties in 2 tests which required them to carry out a number of fairly simple but open-ended tasks over a 15-30 min period. They typically spent too long on individual tasks. All patients scored well on tests of perception, language and intelligence and 2 performed well on a variety of other tests of frontal lobe function. Explanations for their difficulty on the multiple subgoal tasks in terms of memory or motivational problems could be excluded. It is argued that the problem arose from an inability to reactivate after a delay previously-generated intentions when they are not directly signalled by the stimulus situation.

Tim Shallice

Papers

Attention to action: willed and automatic control of behavior

Specific impairments of planning

From Neuropsychology to Mental Structure

Attention to Action: Willed and Automatic Control of Behavior Technical Report No. 8006.

Deficits in strategy application following frontal lobe damage in man