Academic journal article Canadian Journal of Experimental Psychology

Ontogenetic Constraints on Neural and Behavioral Plasticity: Evidence from Imprinting and Face Processing

Academic journal article Canadian Journal of Experimental Psychology

Ontogenetic Constraints on Neural and Behavioral Plasticity: Evidence from Imprinting and Face Processing

Article excerpt

Abstract This paper addresses the extent and limits on brain plasticity during development through the detailed study of imprinting in the domestic chick and the development of face processing in human infants. In both of these systems evidence for constraints on plasticity is reviewed. The first source of constraint comes from the basic architecture of learning mechanisms that support plasticity. With regard to the chick, a specific "Hebbian" model based on the known neural circuitry of the region of the brain involved is presented and discussed. In human infants, a more abstract model inspired by cortical circuitry is mentioned. The second source of constraint comes from biases on the nature of the stimuli selected for attention by the young organism. Both in the chick and the human there is evidence for a subcortical brain system which orients their attention toward conspecifics, and particularly to their faces. It is argued that these systems tutor, or bias the input to, the more plastic learning systems.

This work is inspired by Donald Hebb in two ways. Firstly, he was one of the first to propose a specific model of the relation between the developing brain and behaviour in infants, and also stressed the importance of developmental analyses in thinking about the relation between brain and behaviour. Secondly, his specific ideas on neural plasticity ("Hebbian learning") contributed to the neural network models presented in this paper.

Plasticity and Development

Development is often viewed as a topic somewhat outside the mainstream of the cognitive and neurosciences. In contrast, my reading of Hebb suggests that he viewed development as an essential approach to furthering our understanding of basic questions concerning the relation between neuroscience and cognitive data. Conversely, he also argued that we will only understand development adequately if we bring together evidence from both psychology and neuroscience.1 Following in the footsteps of Hebb, in this chapter I focus on an issue central to the interface between cognition, neuroscience and development: plasticity.

Plasticity in development is something of a double-edged sword. On the one hand, it is clearly advantageous for an organism to be able to absorb information unique to its particular environment, while on the other an organism which responds to every detailed aspect of its environment is unlikely to be viable, for it would learn about many things irrelevant, or even detrimental, to its survival. Another consideration is that building neural circuitry which is appropriately sensitive to the effects of experience is not easy. Such circuitry has to be constructed within certain parameters, otherwise it will not provide an efficient substrate for learning. These considerations lead one to the view that some degree of specification is essential for adaptive plasticity during development. In this chapter I explore some of the constraints and limits on plasticity in development. This exploration will take us, by necessity, from cells to circuits to concepts. In particular, my focus will be on factors which constrain plasticity in the developing cortex.2

In my view, there are three fundamental questions that can be asked about neural plasticity:

1. What is the extent of plasticity in a given neural structure or circuit? That is, is the plasticity a fundamental property of the structure in question, or is it a specialized response to damage?

2. What are the mechanisms of plasticity? Is the basic architecture of the structure modifiable, or does a rigid basic architecture provide the substrate for plasticity of representations?

3. If plasticity is a fundamental property of a neural structure, how is this plasticity constrained such that an adaptive outcome is ensured?

In the next section I will address the first two questions by reviewing evidence from the developmental neurobiology of the cerebral cortex which indicates that (i) plasticity is a widespread and fundamental attribute of the cerebral cortex early in life, and (ii) this plasticity refers to the nature and localization of representations supported by cortex, and not to its basic architecture. …

Search by... Author
Show... All Results Primary Sources Peer-reviewed


An unknown error has occurred. Please click the button below to reload the page. If the problem persists, please try again in a little while.