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  • Cognitive neuroscience: Development and prospects

    MICHAEL I POSNER1, and SHOBINI RAO2

    1Department of Psychology, University of Oregon, Eugene, Oregon 97403, USA2Neuropsychology, NIMHANS, Hosur Road, Bangalore 560 029, India

    e-mail: mposner@uoregon.edu

    The field of cognitive neuroscience has enjoyed an explosive growth following the finding thatspecific brain areas could be activated during processing of visual and auditory words. The subse-quent 20 years have provided a variety of techniques that allow the exploration of brain networksrelated to a large number of cognitive, emotional and social tasks and environments and that haveexamined the formation and loss of these networks over the human life span. This chapter reviewsthe various methods developed for noninvasive exploration of human brain function. Substantivecontributions are then examined in several areas of particular importance to the Indian researchcommunity. These include language, consciousness, brain development and training. We considerthe problems remaining to be explored, and possible practical consequences of the research.

    Cognitive neuroscience is at the intersection of two prior fields: Cognitive psychology and neuro-science. Both these fields have had a relatively short history under these names, although bothhave roots in ancient philosophy [1]. In this chapter, we will examine the modern history of cogni-tive neuroscience, discuss new tools for the noninvasive exploration of the human brain and applythem to several active fields of research. We will attempt to examine both the changes, whichcognitive neuroscience has produced in our understanding of the mind, and in the understand-ing of the brain. In each area, we consider the relevance of the topic to the Indian scientificcommunity.

    1. Cognitive neuroscience

    Cognitive psychology was developed in the 1960s.The work of Herbert Simon and Allen Newell,based upon the general problem solver [2] arguedthat computer programs simulating human perfor-mance could serve as a theory of the mind. Thecomputer metaphor left little scope for studies ofthe brain. At about the same time psychologists,adapting the mathematical theory of communi-cation [3] were able to develop important empiri-cal demonstrations describing human performancein terms of laws governing the rate of informationtransfer [4,5]. These studies served as the basis foran approach to the mind based on empirical studieswhich was synthesized by Ulrich Neisser in his1967 book Cognitive Psychology [6]. Over the years,cognitive psychology branched out to incorporate

    aspects of linguistics, computer science and philo-sophy under the title Cognitive Science [7].

    Neuroscience began in the 1950s as the incorpo-ration of many fields that were interested in thebasic study of the brain. While cognitive psycho-logy mainly studied human beings, the study of thebrain, incorporated work from simpler organismswhose brains were more amenable to anatomicaland physiological methods which were by necessityoften very invasive.

    1.1 Birth of cognitive neuroscience

    The name cognitive neuroscience was coined byGeorge Miller and Michael Gazzaniga during theearly 1980s, when Gazzaniga developed an Insti-tute with that name as part of the grant program ofthe Sloan Foundation related to cognitive science.

    Keywords. Attention; consciousness; cognitive science; language neuroscience; self regulation.

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  • 420 MICHAEL I POSNER AND SHOBINI RAO

    The term neuropsychology, although it had abroader meaning [8] had come to be associatedwith studies of the brain and performance of peoplewith various forms of brain damage. Althoughexcellent work was done in neuropsychology, parti-cularly in distinguishing the different functionsof the two cerebral hemispheres, its use in braininjury cases made it less influential in understand-ing normal human cognition.

    It was not until the late 1980s that neuroimag-ing allowed the normal human brain to be studiedwhile people carried out the kind of tasks whichwere typical in cognitive psychology. The firststudies involved the language system [9]. Thesestudies used a subtractive method adopted fromcognitive psychology to determine activations insensory, motor, phonological, semantic, and atten-tional operations. Probably the most importantoverall result was that even for higher mentalprocesses like word semantics and attention therewere sufficiently common activations to averageacross people. From the work of Karl Lashely [10]and Gestalt Psychologists [11], many believed thathigher mental processes involved the whole brainand did not show any substantial localization.The brain areas involved specifically in semanticprocessing included left ventral frontal lobe, leftposterior tempero-parietal cortex, lateral areas ofthe cerebellum and the dorsal anterior cingulate.Subsequent studies suggested that each area had adifferent function.

    1.2 Implication for brain and mind

    In the twenty years of subsequent imaging studies,some generalizations have emerged about mentalprocesses and about the human brain that supportsthem. These may be summarized under the head-ings of localization, interaction, control, and plas-ticity. Table 1 summarizes many studies involvingmost of the important areas of cognition, emotionand social interaction. Indeed sometimes the termsaffective and social neuroscience are used but mostoften all fields of research are included in the gene-ralized use of the term cognitive neuroscience.

    While there is substantial agreement on thebrain areas activated in studies of attention,memory and language, there is much less agree-ment on the exact function of these areas. In addi-tion to separate localization the areas activatedhave to be coordinated to carry out the task.Although in agreement with patient studies, manytasks involved mainly one cerebral hemisphere (e.g.left for language), most tasks involved activationsin both hemispheres and often in subcortical areassuch as the basal ganglia and cerebellum. Theinteraction among these brain areas in terms of net-works has been a major concern of recent studies.

    Table 1. A list of areas of cognition and emotion forwhich neuroimaging studies have indicated neural net-works involved. One selected study of the each network isreferenced [1222].

    Function Selected reference

    Arithmetic [12]

    Autobiographical Memory [13]

    Fear [14]

    Faces [15]

    Music [16]

    Object Perception [17]

    Reading and Listening [18]

    Reward [19]

    Self Reference [20]

    Spatial Navigation [21]

    Working Memory [22,23]

    Using high density electrical or magnetic record-ings from the scalp in coordination with fMRI,it has been possible to work out the time courseof these activations and learn something aboutthe direction of information flow. These studieshave shown the importance of re-entrant signalsso that sensory areas may be activated in thefirst 100 millisecs from sensory input, but may beactive again by feedback from attentional networksbeyond the first 100 millisecs. These potentiallyoverlapping signals make it difficult to determinethe significance of any activity without a full under-standing of the network involved.

    These new findings have shown that the long-standing serial model of information flow in thehuman brain from primary sensory to secondaryand tertiary association areas is incorrect [23].They also make it more important to understandthe control signals that might provide priority toparticular pathways in any given task. The humanis a learning animal. Ancient networks underly-ing simpler reflex activity present at birth can bereworked through experience allowing much moreplasticity than has previously been supposed [24].

    The activation of many networks are common toall people, suggesting their genetic origins. How-ever, the efficiency with which these networks carryout tasks differ among people and provide ampleopportunity for brain plasticity to influence per-formance. Recent studies have shown how geneby environment interaction shapes these individualdifferences.

    2. Probing human brain networks

    In cellular physiology, the idea of a networkinvolves identified neurons that connect to oneanother by synapses or in some cases through other

  • COGNITIVE NEUROSCIENCE: DEVELOPMENT AND PROSPECTS 421

    Figure 1. Brain networks underlying attention. Onefronto-parietal network is involved in orienting to sensoryevents (circles), while a cingulo-opercular network relates tothe resolution of conflict among responses (triangles, exec-utive network), a third network is responsible for achievingthe alert state involving norepinepherine from the midbrain(squares). [Adapted from 25].

    means of communication. Connectionist models,inspired by neural networks, have considered unitsat particular levels that influence each other bydirect or reciprocal connections. Imaging of humantask performance has identified another level ofnetwork function, which is clearly related to boththe models and the underlying cellular structureby showing that a number of quite separate brainareas must be orchestrated even in a simple task.Each of these areas may be performing a differentcomputation, which taken together allow perfor-mance of the task. Typically cognitive neuroscienceregards the set of activations and their connectionsas the network that underlies task performance.

    In this section, we use attentional networks asan illustration of the methods currently availableto probe the many networks featured in table 1.Attentional networks are special in that their pri-mary purpose is to influence the operation of otherbrain networks. As illustrated in figure 1, threeattentional functions for which brain networks havebeen imaged are: alerting which is involved inacquiring and maintaining the alert

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