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Computational models offer tools for exploring the nature of human
cognitive processes. In connectionist, neural network, or parallel
distributed processing models, information processing takes the
form of cooperative and competitive interactions among many simple,
neuron-like processing units. These models provide new ways of
thinking about the neural basis of cognitive processes, and how
disorders of brain function lead to disorders of cognition. This
monograph is an expanded version of a recent issue of the journal
Cognitive Neuropsychology. It presents the most comprehensive
existing "case study" of how the effects of damage in connectionist
models can replicate the detailed and diverse patterns of cognitive
impairments that can arise in humans as a result of brain damage.
It begins with a review of the basic methodology of cognitive
neuropsychology and of other attempts at modeling
neuropsychological phenomena. It then focuses on a particular form
of acquired reading disorder, "deep dyslexia," in which previously
literate adults with brain damage exhibit a wide range of symptoms
in pronouncing written words, the most striking of which is the
production of semantic errors (e.g. reading RIVER as "ocean"). A
series of simulations investigate the effects of damage in
connectionist models that pronounce written words via their
meaning. The work systematically explores each main aspect of the
design of the models, identifying the basic computational
properties that are responsible for the occurrence of deep dyslexia
when the models are damaged. Although the investigation concerns a
specific form of reading impairment, the computational principles
that emerge as critical are very general ones: representation of
concepts as distributed patterns of activity, encoding of knowledge
in terms of weights on connections between units, interactivity
between units to form stable attractors for familiar activity
patterns, and greater richness of concrete vs. abstract semantics.
The fact that damage to models embodying these principles and
damage to the brain can produce strikingly similar behaviour
supports the view that the human cognitive system operates
according to similar principles.
The scientific study of the human mind and brain has come of age
with the advent of technologically advanced methods for imaging
brain structure and activity in health and disease, plus
computational theories of cognition. These advances are leading to
sophisticated new accounts for how mental processes are implemented
in the human brain, but they also raise new challenges.
Mental Processes in the Human Brain provides an integrative
overview of the rapid advances and future challenges in
understanding the neurobiological basis of mental processes that
are characteristically (and in some cases, perhaps uniquely) human,
including: language; thought; understanding of others; attention;
planning and decision-making; emotion; memory; prediction; and
awareness itself. It also presents the latest insights into how
these various processes can break down after brain injury. With
chapters from some of leading figures in the brain sciences, this
book will be essential for all those in the cognitive and brain
sciences.
This work summarizes the empirical and theoretical work on
impairments of short-term memory (often caused by damage in the
left cerebral hemisphere) and contains chapters from virtually
every scientist in Europe and North America working on the problem.
The chapters present evidence from both normal and brain-damaged
patients. Two neuropsychological issues are discussed in detail:
first, the specific patterns of immediate memory impairment
resulting from brain damage with reference to both multistore and
the interactive-activation theoretical frameworks. Also considered
is the relation between verbal STM and sentence comprehension
disorders in patients with a defective immediate auditory memory:
an area of major controversy in more recent years.
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.
Computational models offer tools for exploring the nature of human
cognitive processes. In connectionist, neural network, or parallel
distributed processing models, information processing takes the
form of cooperative and competitive interactions among many simple,
neuron-like processing units. These models provide new ways of
thinking about the neural basis of cognitive processes, and how
disorders of brain function lead to disorders of cognition. This
monograph is an expanded version of a recent issue of the journal
Cognitive Neuropsychology. It presents the most comprehensive
existing "case study" of how the effects of damage in connectionist
models can replicate the detailed and diverse patterns of cognitive
impairments that can arise in humans as a result of brain damage.
It begins with a review of the basic methodology of cognitive
neuropsychology and of other attempts at modeling
neuropsychological phenomena. It then focuses on a particular form
of acquired reading disorder, "deep dyslexia," in which previously
literate adults with brain damage exhibit a wide range of symptoms
in pronouncing written words, the most striking of which is the
production of semantic errors (e.g. reading RIVER as "ocean"). A
series of simulations investigate the effects of damage in
connectionist models that pronounce written words via their
meaning. The work systematically explores each main aspect of the
design of the models, identifying the basic computational
properties that are responsible for the occurrence of deep dyslexia
when the models are damaged. Although the investigation concerns a
specific form of reading impairment, the computational principles
that emerge as critical are very general ones: representation of
concepts as distributed patterns of activity, encoding of knowledge
in terms of weights on connections between units, interactivity
between units to form stable attractors for familiar activity
patterns, and greater richness of concrete vs. abstract semantics.
The fact that damage to models embodying these principles and
damage to the brain can produce strikingly similar behaviour
supports the view that the human cognitive system operates
according to similar principles.
Brain imaging has been immensely valuable in showing us how the
mind works. However, many of our ideas about how the mind works
come from disciplines like experimental psychology, artificial
intelligence and linguistics, which in their modern form date back
to the computer revolution of the 1940s, and are not strongly
linked to the subdisciplines of biomedicine. Cognitive science and
neuroscience thus have very separate intellectual roots, and very
different styles. Unfortunately, these two areas of knowledge have
not been well integrated as far as higher mental processes are
concerned. So how can these two be reconciled in order to develop a
full understanding of the mind and brain? This is the focus of this
landmark book from leaders in the field. Coming more than two
decades after Shallice's classic 'From neuropsychology to mental
structure', 'The Organisation of Mind' establishes a strong
historical, empirical, and theoretical basis for cognitive
neuroscience. The book starts by reviewing the history and
intellectual roots of the field, looking at some of the researchers
who guided and influenced it. The basic principles - theoretical
and empirical and the inferential relation between them - are then
considered with particular emphasis being placed on inferences to
the organisation of the cognitive system from two empirical
methodologies - neuropsychology and functional imaging. The core
skeleton of the cognitive system is then analysed for the areas
most critical for understanding rational thought. In the third
section the components of simple cognitive acts are described,
namely semantic processing, working memory, and cognitive
operations. In the final section, more complex higher-level
modulating processes are considered, including, supervisory
processing, episodic memory, consciousness and problem-solving.
This will be a seminal publication on the interface between the
brain sciences and the cognitive sciences and essential reading for
all students and researchers in related fields.
This work summarizes the current state of empirical and theoretical
work on impairments of short-term memory (often caused by damage in
the left cerebral hemisphere) and contains chapters from virtually
every scientist in Europe and North America working on the problem.
The chapters present evidence from both normal and brain-damaged
patients, providing a comprehensive view of the functional
characteristics of auditory-verbal short-term memory and its
neurobiological correlates. Two neuropsychological issues are
discussed in detail: the specific patterns of immediate memory
impairment resulting from brain damage, with reference to both
multi-store and the interactive-activation theoretical frameworks,
and the relation between verbal STM and sentence comprehension
disorders in patients with a defective immediate auditory memory,
an area of major controversy in recent years.
As a neuropsychologist, Tim Shallice considers the general question of what can be learned about the operation of the normal cognitive system--including perception, memory, and language--from the study of the cognitive difficulties arising from neurological damage and disease. He distinguishes two type of theories of normal function--primarily modular and primarily non-modular--and argues that the problems of making valid inferences about normal function from studies of brain-damaged subjects are more severe in the latter. He first analyzes five areas in which modularity can be assumed. He then examines these inferences, from group studies, from individual case studies, and from group studies, and from non-modular systems, more theoretically. Finally he considers five areas where theories of normal function are relatively undeveloped and neuropsychologists provide counter-intuitive phenomena and guides to theory-building.
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