Early Development and ParentingEarly Dev. Parent. 7: 121–124 (1998)

Developmental CognitiveNeuroscience: An Overview

Mark H. Johnson*Department of Psychology, Birkbeck College, University of London,London WCIE 7HX, UK

This book presents the case for a new interdisci-plinary field at the interface between develop-mental psychology and cognitive neuroscience:Developmental Cognitive Neuroscience (from hereon the book is referred to as DCN). From theperspective of developmental psychology, theneuroscience approach offers the opportunity ofmore biologically-based accounts of cognitivechange during infancy and childhood. From theperspective of cognitive neuroscience, a devel-opmental approach offers the opportunity ofexamining the construction of an increasinglycomplex brain, and allows us to address suchfundamental questions as the origins of corticalspecificity of function.

One of the most fundamental questions indevelopment concerns the interaction betweengenetic information (nature) and environmentalinformation (nurture). While most agree thatinteraction between these sources of informa-tion is important, few have attempted to specifythis interaction in detail, and behavioural stud-ies with infants are still commonly used tosupport arguments for the importance of eithernature or nurture. A key proposition of DCN isthat a cognitive neuroscience approach cangreatly enhance our thinking about the complexinteraction between intrinsic structure and envi-ronmental information during human develop-ment. When information about cognitive andbrain development is integrated, a picture of theinfant as an active participant in its own postna-tal brain development emerges.

Over the past two decades, brain correlates ofcognitive change have often been taken as evi-dence for ‘maturational’ accounts of cognitivechange. It was often implicitly assumed thatchanges in brain structure indexes the expres-sion of genetic information, and that this thenenabled or triggered new cognitive, perceptualor motor abilities. This has been referred to asthe ‘causal epigenesis’ view (Gottlieb, 1992). Thesurvey of brain development and plasticity inChapter 2 of DCN indicates that, at least forbrain structures that show substantive postnataldevelopment, a ‘probabilistic’ epigenesis view ismore appropriate. By this view, there are two-way interactions between structural and func-tional changes in the brain during development.A neural correlate of a behavioural change doesnot imply a single direction of causality fromgenes to brain to cognition. However, plasticityis a double-edged sword: on the one hand itbuys the organism greater sensitivity to differ-ences in rearing conditions and economises onthe need for extensive genetic specification, buton the other hand it raises the problem of howto ensure a consistent and adaptive outcome tothe developmental process that characterisesmost normal adults. For cognitive neurosciencestudies of adults, this latter issue crystallisesinto how the same representations (e.g. for lan-guage or face processing) emerge in roughly thesame regions of cortex. In DCN I suggest thatresolving this paradox requires us to identifyvarious constraints on cortical plasticity.

In DCN, I follow Elman et al. (1996) in ad-vancing a dissociation between innate represen-tations and innate architecture in the neocortex(the use of the word innate here does not implygenetic determinism, but refers to the productof interactions that occur without influencefrom the external environment). By analogy

* Correspondence to: Department of Psychology, BirkbeckCollege, University of London, Malet Street, London WCIE7HX, UK. E-mail: mark.johnson@psyc.bbk.ac.uk

Contract grant sponsor: UK Medical Research CouncilContract grant sponsor: Human Frontiers Science Founda-tion

CCC 1057–3593/98/030121-04$17.50© 1998 John Wiley & Sons, Ltd.

Received 31 October 1996Accepted 31 October 1996

M.H. Johnson122

with artificial connectionist networks (in whichnodes are joined by links of varying strengths),architecture refers to neuron types, their fre-quency, and their overall patterns of connectiv-ity, while representation refers to the specificpatterns of connectivity between cells (synapses,dendritic arbours, etc.) (see table 1.3 in Elman etal., 1996). Innate architecture defines neural net-works in which the basic architecture of thenetwork is impervious to computations on theinput, and in which the representations (definedby changes in the detailed microcircuitry) thatemerge are constrained by a combination of thebasic architecture and the statistical regularitieswithin the input data. Innate representationrefers to networks in which both the basic archi-tecture of the network (number of nodes, layers,learning rule, and their general patterns of con-nectivity), and the strengths of links (weights)between nodes are ‘hand-wired’ and impervi-ous to the nature of the input. The review ofneurobiological and neuropsychological evi-dence regarding neocortical development andplasticity in DCN reveals no evidence for innaterepresentations, but considerable evidence foran innate common architecture that partiallyconstrains the representations that emergewithin it.

In addition to constraints arising from thebasic architecture of the neocortex, the timing ofdevelopmental events is also critical for deter-mining the location and type of representationsthat emerge within the neocortex (see Elman etal., 1996). Evidence for differential timing dur-ing brain development is also reviewed inChapter 2 of DCN. The greatly extended post-natal phase of brain development that occurs inprimates, and especially humans, relative toother mammals is discussed. This extended pe-riod reveals differential development of bothlayers of the neocortex (with several measuresshowing a postnatal continuation of the prena-tal ‘inside-out’ pattern of growth) and regionsof the neocortex. It is suggested that in somecases, the latter aspect of differential develop-ment may reflect graded spatial waves of devel-opment, rather than discrete localisableprespecified areas. A third notable feature ofpostnatal cortical development concerns the‘rise and fall’ pattern observed in a number ofmeasures such as synaptic density, glucose up-take and levels of some neurotransmitters. Inthe chapters that follow, the sources of architec-

tural and timing constraints on neurocognitivedevelopment in several domains are reviewed.In addition, emphasis is placed on the impor-tance of primitive ‘bootstrapping’ systems instructuring the infant’s early interactions withits external world.

A review of the development of the mecha-nisms of visual perception and orienting revealsthat some subcortical visuo-motor systems areprobably functioning from birth, and providean initial substrate for visually-guided action.Cortical systems gradually increase in their in-fluence over behaviour over the first fewmonths, and representations for perception andaction emerge within these regions, influencedby the infant’s prior interactions with its envi-ronment. For example, neurons in the parietalcortex are important for egocentric/body-cen-tred frames of reference of action. The represen-tations for integrating perception and actionwithin this region likely emerge based on cali-bration of, and mappings between, input andoutput systems. Note that this is not just passiveexperience of visual input, but experience ofacting in the world initially supported by sub-cortical systems. Thus, the infant can be thoughtof as generating the experience necessary for itsown further brain development. Subcortical sys-tems can provide a basis on which corticalspecialisation can be built.

A similar argument can be mounted for thedevelopment of face recognition and aspects ofsocial cognition. A primitive tendency for thenewborn to orient toward face-like patterns bi-ases the infant’s interaction with the world suchthat input to developing cortical circuitry be-comes progressively specialised (through thetuning of microcircuits) for processing this classof stimulus. Thus, representations for face pro-cessing emerge constrained by a combination ofthe general architecture of cortex (and otherbrain regions) and the frequent and protractedexposure to faces early in life (see also deSchonen and Mathivet, 1989). It is suggestedthat deviations in either the architecture of cor-tex, in the environment, or in the infant’s inter-actions with the environment, could result inthe formation of abnormal representationswithin cortical regions.

Aspects of the development of memory canalso be characterised in terms of the increasingspecialisation of cortical microcircuitry. A re-view of the evidence indicates that while the

© 1998 John Wiley & Sons, Ltd. Early Dev. Parent. 7: 121–124 (1998)

An Overview 123

hippocampus is involved in memory forma-tion from birth, neocortical systems probablybecome increasingly involved in memory for-mation over the first year or so of life. A ten-tative proposal is that interaction between thefunctional hippocampus and the developingneocortex may be an additional source of con-straint on the representations that emergewithin the latter.

It is in the domain of language acquisitionthat some of the strongest claims about pre-specified (innate) specialised cortical circuitryhave been made (e.g. Pinker, 1994). In DCN avariety of sources of evidence are reviewedsuggesting that regions of the left temporalcortex may be a preferentially favoured, butnon-essential, substrate for speech processingby virtue of its efficiency at dealing withrapid temporal transitions. However, there islittle conclusive evidence for an ‘innate lan-guage module’ in the sense of innate represen-tations. Rather, it is suggested that corticalmicrocircuitry becomes increasingly specialisedfor language processing constrained by the na-ture of the input, and the general architectureof the neocortex.

In Chapters 7 and 8, I focus on constraintsderived from developmental timing (referredto as ‘chronotopic constraints’ by Elman et al.,1996). Two examples of this come from thetwo hemispheres having slightly different de-velopmental timetables, and from the anterior(frontal) regions of cortex being delayed inspecialisation relative more posterior regionsof cortex. I suggest that regions of the neocor-tex that are relatively delayed in their speciali-sation have the opportunity to (i) integrateinformation over larger spatial and temporalgaps, and (ii) regulate the functioning of earlydeveloping systems. Both of these are charac-teristics of the frontal cortex. Evidence for ac-tivity in frontal regions early in life suggeststhat the region may undergo progressivewaves of specialisation, rather than having asingle onset of functioning. Another aspect ofbeing on a differential timetable of develop-ment is that this may result in subtle differ-ences in architecture between parts of cortex,such as in the extent of dendritic aroborisationat a given point in time. Such differences maybe the basis for hemispheric lateralisation. Forexample, if one hemisphere is delayed relativeto another it may have a greater proportion of

short range connections relative to long range.This apparently minor architectural differencemay mean that one side is better able to pro-cess certain kinds of information, and thus ‘at-tract’ certain types of computation (see also deSchonen et al., 1993). Mutual inhibition be-tween the hemispheres may then acceleratethis specialisation process.

A primary focus of DCN is on constraintson the emergence of representations withinthe cortex. Chapter 9 turns to the representa-tions themselves, and specifically to the mech-anisms of representational change duringdevelopment. It is tentatively suggested thatan understanding of the principles governingthe remapping of information within the cor-tex will illuminate the process of cognitivechange, referred to as ‘representational re-description’ (Karmiloff-Smith, 1992). A provi-sional sketch of some candidate mechanisms isprovided. One of the processes involved inthe emergence of cortical representations is se-lectionism, a process through which synapticand dendritic loss can increase the specificityof an initially undifferentiated cortical sub-strate. Different variations of selectionism areoutlined, and are contrasted with a recent pro-posal for directed dendritic growth (Quartzand Sejnowski, in press). A result of selectiveloss can be the increasing parcellation (infor-mational encapsulation) of neural circuits. Anumber of information processing and be-havioural consequences of this process are dis-cussed, including the increasing ‘modulari-sation’ of the brain during development. Pos-sible consequences of the increasing strengthof representations are explored through a sim-ple connectionist model that simulates the dis-sociation between reaching and lookingmeasures of object permanence in infants.

Finally, DCN returns to the question ofthe genetic contribution to brain and cogni-tive development. It is argued that the gene-tic contribution to cognition can only beinterpreted within a developmental cognitiveneuroscience analysis that includes some ac-count of the interactions at molecular, cellu-lar and organism-environment levels. Inparticular, it seems unlikely that patterns ofcortical specificity are encoded by genes. Theimplications of the conclusions in DCN for de-velopmental disorders are also discussed.

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It is argued that applying the adult static neu-ropsychology approach to such disorders is un-likely to be fruitful. Rather, I suggest thatneurocomputational modelling of deviant de-velopmental pathways may give us insightsinto the processes of (i) recovery of functionfollowing early abnormality, and (ii) increasingdeviations from the normal developmentalpathway resulting from newborn brain architec-ture defects. I conclude with my belief thatdevelopmental cognitive neuroscience will soonbecome the most exciting and fastest movingnew discipline within the cognitive and neuralsciences.

ACKNOWLEDGEMENTS

I acknowledge the current financial supportfrom the UK Medical Research Council and theHuman Frontiers Science Foundation. Thanks toAnnette Karmiloff-Smith for comments on thisprecis. Collaborators who have contributed tothe ideas in DCN are acknowledged in thebook.

REFERENCES

de Schonen, S. and Mathivet, E. (1989). First come,first serve: a scenario about the development ofhemispheric specialisation in face recognition dur-ing infancy. European Bulletin of Cognitive Psychol-ogy, 9, 3–44.

de Schonen, S., Deruelle, C., Mancini, J. and Pascalis,O. (1993). Face processing by the right and lefthemispheres and maturational heterochronies. Inde Boysson-Bardies et al. (Eds), Developmental Neu-rocognition: Speech and Face Processing in the FirstYear of Life. Dordrecht: Kluwer.

Elman, J.L., Bates, E.A., Johnson, M.H., Karmiloff-Smith, A., Parisi, D. and Plunkett, K. (1996). Re-thinking Innateness: A Connectionist Perspective onDevelopment. Cambridge, MA: MIT Press/Bradford.

Gottlieb, G. (1992). Individual Development and Evolu-tion: The Genesis of Novel Behavior. New York: Ox-ford University Press.

Karmiloff-Smith, A. (1992). Beyond Modularity: A De-velopmental Perspective on Cognitive Science. Cam-bridge, ME: MIT Press/Bradford.

Pinker, S. (1994). The Language Instinct: How the MindCreates Language. New York: William Morrow.

Quartz, S.R. and Sejnowski, T.J. (1998), The neuralbasis of cognitive development: A constructivistmanifesto. Behavioural and Brain Sciences, in press.

© 1998 John Wiley & Sons, Ltd. Early Dev. Parent. 7: 121–124 (1998)