- Email: [email protected]
Brain activity and cognitive processes: introduction to the special issue
Acta Psychologica 105 (2000) 123±126
www.elsevier.com/locate/actpsy
Editorial
Brain activity and cognitive processes: introduction to the special issue Characteristic of the cognitive revolution that swept away the scienti®c doctrine of behaviorism some 40 years ago is the attempt to understand the inner workings of the 'black box'. Almost from the start, this has led to a longstanding debate concerning the optimal level of description of cognitive functions (the symbolic-computational versus the subsymbolic-implementational controversy). Although the debate is still not settled, there is general consensus that knowledge of the biological realization of cognitive functions is of great importance in guiding our understanding of them. For a long time, the main problem in this endeavor has been the impossibility of directly observing the processes and mechanisms of the brain underlying cognitive operations. As a consequence, cognitive psychology has had to resort to indirect ways of theorizing about the brain±behavior relationship by: (1) speculating about possible brain systems and processes operative in cognitive tasks based on analyzing the eects of experimental manipulations on performance and (2) using insights from the neurosciences, especially neuropsychology, about global relationships between brain structure and cognitive function. This situation has changed fundamentally by the technological advancements in neuroimaging techniques. Now, for the ®rst time, it has become possible to measure on-line activity in the brain while it is carrying out cognitive tasks. Of course, the excitement about the ability to chart brain activity during cognitive processes has to be mitigated by the realization that the available techniques still have limitations. There are limitations in temporal and spatial resolution, and interpreting the data does pose certain problems. Moreover, the application of the techniques requires laborious procedures and poses several constraints on subjects, tasks and situations to be studied. Also, the methodological consistency required for reliability and replicability leaves much to be desired. Despite all these limitations and problems, it is clear that neuroimaging has become a major tool for the advancement of our understanding of the relationship between the brain and cognition. The main perspective of applying neuroimaging to cognition is to determine the functional signi®cance of particular brain areas. Such ®ndings can be used to check and correct existing ideas about the specialized functions of brain areas derived from 0001-6918/00/$ - see front matter Ó 2000 Elsevier Science B.V. All rights reserved. PII: S 0 0 0 1 - 6 9 1 8 ( 0 0 ) 0 0 0 5 6 - 1
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neuroanatomical analyses and observations of the behavioral eects of brain lesions. Eventually, neuroimaging will allow a highly detailed speci®cation of cognitive functions and their localization in the brain. Of course, this is not to argue that there will be found a simple and one-to-one relationship between activity in certain brain areas and cognitive performance. A given brain region may play dierent roles depending on its interactions with other regions involved in performing a cognitive task. Also, it has become clear that there are inter-individual dierences and that cognitive functions may be compensated by other brain areas than the ones normally involved. Knowledge of such details, however, is exactly what is needed to get a better understanding of the workings of the brain in carrying out cognitive operations. Neuroimaging will not provide the answers to all our questions about the brain± behavior relationship. Knowing that a particular brain area is involved in performing a cognitive activity does not by itself tell us how it is done. We need other tools, like neural network modeling, to explore and understand how brain areas perform cognitive operations. Moreover, to expand the insights into how cognitive operations and functions are accomplished in the brain, we need to integrate knowledge at an even more detailed level, the level of the individual neuron and its various modulating mechanisms. Yet, charting the details of the functional role of brain regions in carrying out cognitive operations is an essential step in the enterprise of brain±behavior research. It provides the basic insights needed to constrain psychological models of cognition. Speculations about cognitive mechanisms and processes have to be guided by knowledge of the detailed architecture of active and inactive brain areas. Moreover, this knowledge is indispensable to the further development of models explaining how these cognitive mechanisms and processes are implemented in the neural system. At the end of the `decade of the brain', the interdisciplinary ®eld of cognitive neurosciences is thriving. Neuroscienti®c methods, like neuroimaging, have attracted the attention of many scientists, including those working on human cognition from more traditional perspectives, like experimental psychology and psychonomics. Therefore, the editorial board of Acta Psychologica has decided to devote two special issues contributing to the domain of cognitive neuroscience. The second of these issues, scheduled to appear in 2001, will be a re¯ection on the achievements, promises and limitations of cognitive neuroscience. This ®rst special issue is more empirically oriented. Several of the contributions collected in this issue were part of a symposium organized by Lars Nyberg on ``Functional neuroimaging of human memory'' during the XXVII International Congress of Psychology held in Stockholm, Sweden, this year. In the spirit of cognitive neuroscience, the contributions represent dierent brain imaging techniques (MEG, PET, fMRI), and involve normal as well as disordered subject populations. It was clear from the symposium that brain imaging is now used to address questions at a very detailed level of analysis. This ranges from identifying the speci®c conditions under which certain types of regional activation are observed, to analysis of how whole-brain activity changes in relation to various ways of quantifying learning. This way of using functional neuroimaging is accompanied by an increased sophistication in analyzing the data.
Editorial
125
The papers in this special issue are representative of the recent developments in study design, data collection and data analysis that the ®eld has witnessed. The ®rst four papers present some original neuroimaging ®ndings during encoding and retrieval in memory tasks. In the contribution by Buckner, Logan, Donaldson and Wheeler, data are presented about frontal cortical activation during shallow and deep encoding in an episodic memory task. It is concluded that dierent cortical areas active during encoding provide input to medial temporal structures, where they are bound to form episodic memory. Habib, McIntosh and Tulving present results showing that neuroimaging data can be used to study inter-individual dierences in brain areas engaged in various phases of a verbal discrimination learning task. In the next paper, brain activation is measured during encoding and retrieval of pictures and words. K ohler, Moscovitch, Winocur and McIntosh show that, during encoding, dierent activation patterns appear in widespread cortical regions, both lateral and bilateral. They conclude that there are both task (encoding or retrieval)-speci®c and format (words or pictures)-speci®c activation patterns. Although the strongest retrieval-related increases in activity are common to men and women, Nyberg, Habib and Herlitz conclude that there are speci®c dierences in brain areas activated in men and women that may underlie behavioral sex dierences in episodic memory tasks. In the second group of four papers, more general issues are discussed by reviewing existing ®ndings. The contribution of D uzel emphasizes the distinction between sustained neural activation correlated with a particular `processing mode', or cumulative eects of item sequences, and short-lasting activation patterns correlated with individual item events. Hugdahl reviews recent evidence on the lateralization of cognitive processes in the brain. Although various quali®cations are necessary, the old notion of a basic specialization of the left hemisphere for language and the right hemisphere for visuo-spatial functions still remains a dichotomy for which there is substantial empirical support. R onnberg, S oderfeldt and Risberg discuss the neuroscience of sign language. Interestingly, there appears to be a left hemisphere dominance for the perception and production of sign language similar to spoken language, but there is also a speci®c role for the right hemisphere. It is argued that neuroimaging studies of sign language may illuminate reorganization of cognitive functions and plasticity of the brain. The contribution of Almkvist gives an overview of some of the neuroimaging results in studying various cognitive processes in the normal and the pathological aging brain of Alzheimer's patients. Acknowledgements We would like to thank the following persons for their willingness to act as reviewers for the papers submitted to this special issue and we gratefully acknowledge their contribution: J.B. Hellige (University of South California), John Gabrieli (Stanford University), Bencie Woll (City University of London), Philip Scheltens (Free University of Amsterdam), Lars-G oran Nilsson (Stockholm University),
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Editorial
Anthony Wagner (Harvard University), Michael Rugg (University of St Andrews) and Fergus Craik (University of Toronto). Gezinus Wolters Department of Psychology, University of Leiden, P.O. Box 9555, 2300 RB Leiden, The Netherlands E-mail address: [email protected] Lars Nyberg Department of Psychology, Umea University, S-901 87 Umea, Sweden E-mail address: [email protected]
www.elsevier.com/locate/actpsy
Editorial
Brain activity and cognitive processes: introduction to the special issue Characteristic of the cognitive revolution that swept away the scienti®c doctrine of behaviorism some 40 years ago is the attempt to understand the inner workings of the 'black box'. Almost from the start, this has led to a longstanding debate concerning the optimal level of description of cognitive functions (the symbolic-computational versus the subsymbolic-implementational controversy). Although the debate is still not settled, there is general consensus that knowledge of the biological realization of cognitive functions is of great importance in guiding our understanding of them. For a long time, the main problem in this endeavor has been the impossibility of directly observing the processes and mechanisms of the brain underlying cognitive operations. As a consequence, cognitive psychology has had to resort to indirect ways of theorizing about the brain±behavior relationship by: (1) speculating about possible brain systems and processes operative in cognitive tasks based on analyzing the eects of experimental manipulations on performance and (2) using insights from the neurosciences, especially neuropsychology, about global relationships between brain structure and cognitive function. This situation has changed fundamentally by the technological advancements in neuroimaging techniques. Now, for the ®rst time, it has become possible to measure on-line activity in the brain while it is carrying out cognitive tasks. Of course, the excitement about the ability to chart brain activity during cognitive processes has to be mitigated by the realization that the available techniques still have limitations. There are limitations in temporal and spatial resolution, and interpreting the data does pose certain problems. Moreover, the application of the techniques requires laborious procedures and poses several constraints on subjects, tasks and situations to be studied. Also, the methodological consistency required for reliability and replicability leaves much to be desired. Despite all these limitations and problems, it is clear that neuroimaging has become a major tool for the advancement of our understanding of the relationship between the brain and cognition. The main perspective of applying neuroimaging to cognition is to determine the functional signi®cance of particular brain areas. Such ®ndings can be used to check and correct existing ideas about the specialized functions of brain areas derived from 0001-6918/00/$ - see front matter Ó 2000 Elsevier Science B.V. All rights reserved. PII: S 0 0 0 1 - 6 9 1 8 ( 0 0 ) 0 0 0 5 6 - 1
124
Editorial
neuroanatomical analyses and observations of the behavioral eects of brain lesions. Eventually, neuroimaging will allow a highly detailed speci®cation of cognitive functions and their localization in the brain. Of course, this is not to argue that there will be found a simple and one-to-one relationship between activity in certain brain areas and cognitive performance. A given brain region may play dierent roles depending on its interactions with other regions involved in performing a cognitive task. Also, it has become clear that there are inter-individual dierences and that cognitive functions may be compensated by other brain areas than the ones normally involved. Knowledge of such details, however, is exactly what is needed to get a better understanding of the workings of the brain in carrying out cognitive operations. Neuroimaging will not provide the answers to all our questions about the brain± behavior relationship. Knowing that a particular brain area is involved in performing a cognitive activity does not by itself tell us how it is done. We need other tools, like neural network modeling, to explore and understand how brain areas perform cognitive operations. Moreover, to expand the insights into how cognitive operations and functions are accomplished in the brain, we need to integrate knowledge at an even more detailed level, the level of the individual neuron and its various modulating mechanisms. Yet, charting the details of the functional role of brain regions in carrying out cognitive operations is an essential step in the enterprise of brain±behavior research. It provides the basic insights needed to constrain psychological models of cognition. Speculations about cognitive mechanisms and processes have to be guided by knowledge of the detailed architecture of active and inactive brain areas. Moreover, this knowledge is indispensable to the further development of models explaining how these cognitive mechanisms and processes are implemented in the neural system. At the end of the `decade of the brain', the interdisciplinary ®eld of cognitive neurosciences is thriving. Neuroscienti®c methods, like neuroimaging, have attracted the attention of many scientists, including those working on human cognition from more traditional perspectives, like experimental psychology and psychonomics. Therefore, the editorial board of Acta Psychologica has decided to devote two special issues contributing to the domain of cognitive neuroscience. The second of these issues, scheduled to appear in 2001, will be a re¯ection on the achievements, promises and limitations of cognitive neuroscience. This ®rst special issue is more empirically oriented. Several of the contributions collected in this issue were part of a symposium organized by Lars Nyberg on ``Functional neuroimaging of human memory'' during the XXVII International Congress of Psychology held in Stockholm, Sweden, this year. In the spirit of cognitive neuroscience, the contributions represent dierent brain imaging techniques (MEG, PET, fMRI), and involve normal as well as disordered subject populations. It was clear from the symposium that brain imaging is now used to address questions at a very detailed level of analysis. This ranges from identifying the speci®c conditions under which certain types of regional activation are observed, to analysis of how whole-brain activity changes in relation to various ways of quantifying learning. This way of using functional neuroimaging is accompanied by an increased sophistication in analyzing the data.
Editorial
125
The papers in this special issue are representative of the recent developments in study design, data collection and data analysis that the ®eld has witnessed. The ®rst four papers present some original neuroimaging ®ndings during encoding and retrieval in memory tasks. In the contribution by Buckner, Logan, Donaldson and Wheeler, data are presented about frontal cortical activation during shallow and deep encoding in an episodic memory task. It is concluded that dierent cortical areas active during encoding provide input to medial temporal structures, where they are bound to form episodic memory. Habib, McIntosh and Tulving present results showing that neuroimaging data can be used to study inter-individual dierences in brain areas engaged in various phases of a verbal discrimination learning task. In the next paper, brain activation is measured during encoding and retrieval of pictures and words. K ohler, Moscovitch, Winocur and McIntosh show that, during encoding, dierent activation patterns appear in widespread cortical regions, both lateral and bilateral. They conclude that there are both task (encoding or retrieval)-speci®c and format (words or pictures)-speci®c activation patterns. Although the strongest retrieval-related increases in activity are common to men and women, Nyberg, Habib and Herlitz conclude that there are speci®c dierences in brain areas activated in men and women that may underlie behavioral sex dierences in episodic memory tasks. In the second group of four papers, more general issues are discussed by reviewing existing ®ndings. The contribution of D uzel emphasizes the distinction between sustained neural activation correlated with a particular `processing mode', or cumulative eects of item sequences, and short-lasting activation patterns correlated with individual item events. Hugdahl reviews recent evidence on the lateralization of cognitive processes in the brain. Although various quali®cations are necessary, the old notion of a basic specialization of the left hemisphere for language and the right hemisphere for visuo-spatial functions still remains a dichotomy for which there is substantial empirical support. R onnberg, S oderfeldt and Risberg discuss the neuroscience of sign language. Interestingly, there appears to be a left hemisphere dominance for the perception and production of sign language similar to spoken language, but there is also a speci®c role for the right hemisphere. It is argued that neuroimaging studies of sign language may illuminate reorganization of cognitive functions and plasticity of the brain. The contribution of Almkvist gives an overview of some of the neuroimaging results in studying various cognitive processes in the normal and the pathological aging brain of Alzheimer's patients. Acknowledgements We would like to thank the following persons for their willingness to act as reviewers for the papers submitted to this special issue and we gratefully acknowledge their contribution: J.B. Hellige (University of South California), John Gabrieli (Stanford University), Bencie Woll (City University of London), Philip Scheltens (Free University of Amsterdam), Lars-G oran Nilsson (Stockholm University),
126
Editorial
Anthony Wagner (Harvard University), Michael Rugg (University of St Andrews) and Fergus Craik (University of Toronto). Gezinus Wolters Department of Psychology, University of Leiden, P.O. Box 9555, 2300 RB Leiden, The Netherlands E-mail address: [email protected] Lars Nyberg Department of Psychology, Umea University, S-901 87 Umea, Sweden E-mail address: [email protected]