Functions of the Brain

A Conceptual Approach to Cognitive Neuroscience

Albert Kok

• Publisher: Routledge
• Year: 2019
• ISBN:
  9780429835902
• Edition: 1
• Topic: Psychology
• Subtopic: History & Theory in Psychology
• Index: Psychology

Considering how computational properties of the brain inform cognitive functions, this book presents a unique conceptual introduction to cognitive neuroscience. This essential guide explores the complex relationship between the mind and the brain, building upon the authors' extensive research in neural information processing and cognitive neuroscience to provide a comprehensive overview of the field.

Rather than providing detailed descriptions of different cognitive processes, Functions of the Brain: A Conceptual Approach to Cognitive Neuroscience focuses on how the brain functions using specific processes. Beginning with a brief history of early cognitive neuroscience research, Kok goes on to discuss how information is represented and processed in the brain before considering the underlying functional organization of larger-scale brain networks involved in human cognition. The second half of the book addresses the architecture of important overlapping areas of cognition, including attention and consciousness, perception and action, and memory and emotion.

This book is essential reading for upper-level undergraduates studying Cognitive Neuroscience, particularly those taking a more conceptual approach to the topic.

1 The birth of cognitive neuroscience

Contents

• Introduction
• The development of cognitive neuroscience
• The mind-brain
• Methods in cognitive brain research

Introduction

Cognitive psychology is committed to the study of cognition, a domain traditionally considered as the ‘home base’ of functions like perception, attention, memory, language and consciousness. Human cognition, the ‘knowing part’ of our mind is nonetheless functionally related to another domain of the human mind, emotion, even though they correspond with different divisions of the brain. Emotions and its ‘feeling part’ color cognitive processes and events that we experience or recall. In turn, cognitive processes can influence and control emotional processes. When faced with uncertainty, human organisms will not only engage areas in the brain that developed relatively late in the course of evolution, like the neocortex. Even complex decisions may then appeal to evolutionarily old structures in the limbic system that regulate affective processes. The fusion between rational and irrational processes that often underlies human social decision making (Tversky & Kahneman, 1981; Damasio, 1994) indicates that human emotions and their underlying mechanisms are essential elements to be considered in the study of human cognition.

The central issue addressed in the present chapter is how we can conceptualize the relationship between mind and brain and their constituting parts. This will necessarily lead us back to some questions that were initially raised in cognitive psychology as well as in neuroscience, but later were reunited in cognitive neuroscience.

Our daily behavior depends to a large extent on the amalgam of cognitive and emotional functions, glued together in the seamless unity of our conscious or unconscious mind. Nonetheless, the principal task of cognitive psychology is not to understand the workings of the ‘full mind’ as represented in our daily experiences, but rather to unravel its covert structure and functional sub-components.¹ For example, recognizing a familiar face might be dissected into two subcomponents: analyzing its perceptual features (the shape of face, eyes and mouth), and the subsequent search for a match of the perceptual image with representations stored in long-term memory. The temporal aspects of these processes are also a crucial part of the unraveling process: does the analysis of perceptual characteristics precede recognition, or do both processes run in parallel?

Current investigators of the human mind will probably accept the idea that cognitive and emotional processes arise from the complex machinery of the brain, which in turn is the product of successive adaptations during a long biological evolution. But for over a century, cognitive psychology and neuroscience were strictly separate research domains. This ‘separation of disciplines’ has a long history with interesting cyclic trends. For example, at the end of the 19th century psychologists were particularly interested in the integration of physiology and psychology. In fact, psychology began as Physiological Psychology. Both Wilhelm Wundt and William James, the founders of experimental psychology in Europe and the United States respectively, were fascinated by the question how properties of the brain and mind were related to one another (Boring, 1929). But in the following decades, the interest of psychologists shifted gradually towards the subjective quality of the human mind with introspection as their major tool, to subjectively experience or ‘understand’ mental states.

The development of cognitive neuroscience

Modern cognitive neuroscience, a core issue of the present book, did not drop from heaven but evolved in the 20th century as the product of some crucial steps in the history of the scientific study of the human mind. The brief historical perspective presented ahead may clarify why a central notion of cognitive neuroscience that the ‘mind is a product of brain’, developed relatively late in the 20th century.

Behaviorism

In the mid-20th century behaviorism was the first step in the transition of a predominantly subjective psychology into an objective science of behavior. Since it abandoned all ‘mentalist’ concepts and methods as introspection, it became known as ‘black-box’ psychology, psychology without a mind (Figure 1.1).

Behaviorists placed much emphasis on changes in behavior caused by external stimuli and rewards, which they regarded as the central subject of scientific research. Physiology, as manifested in the activity of muscles and the autonomic nervous system, was reinstated, providing as it did a valuable source of information of the body’s reflexive responses to external stimuli. A second important spin-off of behaviorism was research techniques, like classical and instrumental conditioning, which were ideally suited for application in experimental animal research. Even today, conditioning remains the principal tool in neurobiology to study ‘cognition’, i.e. elementary learning and memory processes in animals. The rationale of behaviorism was that knowledge of the laws of behavior of laboratory animals could also be useful to gain insight into cognitive learning in humans.

In this respect, behaviorism came much closer to principles of evolutionary thinking, as represented in Darwin’s theory of natural selection (Darwin, 1859), than earlier, more cognitively oriented movements in psychology like Gestalt psychology and Jean Piaget’s fundamental theory of development.

Figure 1.1
Three steps in the development of cognitive neuroscience. Step 1, Behaviorism as a reaction to the predominantly subjective character of psychology. Step 2, the rebirth of Cognitive Psychology is accompanied by a renewed interest in processes within the black box, but with no reference to the brain. Step 3: Cognitive Neuroscience describes mental processes at the level of the mind as well as the brain.

Cognitive psychology

The second crucial step in the development of cognitive neuroscience took place in the early 1960s. It was the renewed interest in higher mental processes, a movement also known as a cognitive revival or ‘shift’. The central mission of the new cognitive psychology or ‘cognitivism’ was to fill the mental vacuum created by behaviorism: cognitive psychology re-opened the black box by paying attention to the higher mental processes as the hidden causes of behavior.

But it also appeared that the practitioners of this new cognitive psychology showed little interest in the neural substrates of human behavior. It remained typically a ‘dry mind’ approach of psychology, as Kosslyn and Koenig (1992) characterized it so aptly it in their seminal introductory book. A possible reason why is that research into physiological processes was still strongly associated with the behaviorist tradition. Another factor was that cognitive psychology was predominantly ‘functionalistic’, i.e. primarily focused on functions and its manifestations in behavior, rather than its neural substrate. The functionalistic character of this new cognitive psychology was also clearly manifested in the frequent use of the computer as a metaphor – or model – of mental processes.

Indeed, the computer invented by two brilliant pioneers, Alan Turing and John von Neumann, now emerged as a powerful tool that allowed to formulate more precisely theories of brain functioning. A device invented by Turing called ‘Turing machine’ provided the basic ingredients of a computer program. A Turing machine is an idealized and amazingly simple computing device consisting of a read/write head (or ‘scanner’) with a paper tape passing through it. The tape is divided into squares, each square bearing a single symbol ‘0’ or ‘1’. The machine changes symbols by deleting or changing its content. The tape is the machine’s general-purpose storage medium, serving both as the vehicle for input and output and as a working memory for storing the results of intermediate steps of the computation. Turing’s abstract conceptualization of a computing system also formed the framework of von Neumann’s design of the architecture of the electronic digital computer with parts consisting of a processing unit, and mass storage unit and input and output mechanisms. This system contained all the elements necessary to describe a basic information processing system as implemented in cognitively oriented models.

Another area of research becoming an essential element of cognitive psychology from the 1950s onwards was the information processing approach. The main focus of information processing theories in psychology concerned isolating information processing stages that reflected successive transformations of information, flowing from stimulus to a motor response. Its principal initiators were Broadbent (1958), Sternberg (1969) and Atkinson and Shiffrin (1968). Sternberg’s approach focused primarily on the analysis of choice reaction task measures, with no direct reference to the brain. The statistical relationship between task variables affecting performance, in fact, served as the primary tool to isolate stages as independent (‘additive’) factors. Information processing paradigms, typically accompanied by diagrams of ‘arrows and boxes’ stimulated a renewed interest in mental chronometry, as initially conceived by the Dutch optical physiologist Donders (1869). This held in particular for the timing of processes, like early and late selection in selective attention tasks, and processes like stimulus evaluation, decision and memory search and response preparation in choice reaction and memory search tasks (Sternberg, 1969; Sanders, 1983; Shiffrin & Schneider, 1977).

Cognitive neuroscience

At the end of the 20th century cognitive experimental psychologists started using a new version of the choice reaction task called ‘conflict’ task, supplemented with physiological measures like the electromyogram (muscle activity) of the involved lower arm, and the Lateralized Readiness Potential (LRP; an electrophysiological scalp-recorded measure of the brain reflecting motor preparation). In the conflict paradigm the target (for example a central arrow or bracket sign) is flanked by non-target stimuli which correspond either with the same directional response as the target (congruent flankers, e. g. > > > > >), or with the opposite response (incongruent flankers < < > < <), or with neither (neutral flankers, e.g. x x > x x) (Eriksen & Eriksen, 1974). Incongruent targets typically elicited longer Rts than neutral or congruent trials. Physiological results obtained with the paradigm provided additional insights into the serial versus parallel nature of information processes. Incongruent stimulus elicited ‘incorrect’ muscle and motor activity of the brain, before the occurrence of the overt correct button press response. The combined use of behavioral and psychophysiological measures thus suggested a parallel activation of stimulus and response related information channels.

Another area in which behavioral and electrical recordings of brain activity contributed to elucidating the neural mechanism underlying mental processes was that of selective human attention. The studies were particularly useful because they revealed an essential function of human spatial attention in increasing the ‘sensory gain’ of perceptual processes in a relatively early phase of the processing sequence. This effect became apparent in the enhancement of early scalp-recorded brain potentials (P1, N1), elicited by visual stimuli presented at attended relative to unattended locations of the subject’s visual field (Mangun & Hillyard, 1995; Desimone & Duncan, 1995).²

These studies foreboded the birth of cognitive neuroscience, a discipline which took the characteristics of the brain into account when describing the characteristics of the human mind. One might say that opening the black box of behaviorism not only brought back the mind but also revealed the organ that produced the mind: the human brain. Unlike the mind, the brain and its networks are physical substances obeying the same physical laws as other physical substances (see Figure 1.1 lower panel). Mental processes could now be described concurrently at both the mental and neural levels, with the human brain serving as the ‘organ’ or biological hardware, in which the mental software was implemented.

In addition to electrophysiological measures, a new and powerful tool, functional imaging (fMRI) of the blood flow within the brain, allowed to further explore the spatial characteristics of large-scale networks, activated during performance of a cognitive task (see Gazzaniga et al., 2002 for an early overview). Cognitive researchers gradually became more inclined to consider neural constraints in the modeling of mental processes, i.e. the limiting conditions imposed by the central nervous system as the neural substrate of the human mind. This research included animal studies focusing on neural processes at the micro level, using micro-electrodes to probe action and synaptic potentials reflecting the transmission of information in the brain. At the macro level, cognitive activity as regulated by larger functional units and networks in t...