Elsevier

Neural Networks

Volume 13, Issues 8–9, November 2000, Pages 861-870
Neural Networks

2000 Special Issue
Towards a network theory of cognition

https://doi.org/10.1016/S0893-6080(00)00059-9Get rights and content

Abstract

For cognitive neuroscience to go forward a more explicit effort is needed to use neurophysiology to constrain how the brain produces human mental functions. This review begins with the suggestion that two fundamental features may be critical for this effort. The first is the connectivity of the brain, which occupies an intermediate position between complete redundant interconnections and independence. The term semiconnected is presented as a designation, which is an obvious derivation of the term semiconductors as used in engineering. The second is transient response plasticity where a given neuron or collection of neurons may show rapid changes in response characteristics depending on experience. Response plasticity is a ubiquitous property of the brain rather than a unique characteristic of “neurocognitive” regions. These two properties may be brought together when brain areas interact such that their aggregate function embodies cognition. Three examples are used to illustrate these general principles and to develop the idea that a particular region in isolation may not act as a reliable index for a particular cognitive function. Instead, the neural context in which an area is active may define the cognitive function. Neural context emphasizes that the particular spatiotemporal pattern of neural interactions may hold the key to bridge between brain and mind.

Section snippets

Connectivity maximizes flexibility of information processing and representation

One prominent feature of the brain is connectivity. Neurons are linked to one another both locally and at a distance. Most other systems in the body show some capacity for cell to cell communication, but the nervous system appears to be specialized for rapid transfer of signals. Physiologically, this means that a single change to the system is conveyed to several parts of the brain simultaneously and that some of this will feed back onto the initial site. There are obvious extremes to just how

Transient response plasticity in the CNS is ubiquitous

Neural plasticity is an established phenomenon. Following central or peripheral damage there is profound reorganization of the nervous system (Hubel and Wiesel, 1965, Merzenich et al., 1983, Pons et al., 1991. Reorganization also can be observed after prolonged training (Karni et al., 1995). The plasticity considered here is more short-lived. Cells can show a rapid shift in response to afferent stimulation that is dependent on the context in which they fire. This transient response plasticity

Aggregate properties of neural populations

The idea of “neural aggregates” has some history and has been used to characterize brain theories that strike an intermediate position between strict localization of function and a holistic approach. Aggregate theories acknowledge that certain functions, usually sensory and motor, may be localizable, but higher-order function results from the combined, or aggregate, operations of several areas (Lashley, 1929). Recent examples of aggregate theories state that cognitive processes result from the

Neural context

The idea of a neural context is meant to underscore the importance of considering activity of the entire brain rather than individual regions. Activity of the area may be equivalent across several seemingly different cognitive tasks. What distinguishes tasks is the pattern of spatiotemporal activity and interactivity more than the participation of any particular region. Through its connectivity and basic response properties, large neural systems are engaged starting from the sensory systems,

Implications for cognition

Neurophysiology and cognitive psychology have developed independently across the centuries. There is no necessity for the two disciplines to influence each other. Neurophysiology has evolved partly from study of the basic properties of neurons without much link to overt behaviour beyond simple reflexes. Conversely, cognitive psychology has developed through careful experimental investigation of overt behaviour and how the manipulations of putative cognitive processes change the measured

Acknowledgements

The contributions of several of my colleagues to the development of the ideas expressed here are gratefully acknowledged: Drs B. Horwitz, JM Jennings, E Tulving, L Nyberg, R Cabeza, and NJ Lobaugh. AR McIntosh is supported by the Natural Sciences and Engineering Council of Canada and the Medical Research Council of Canada (grant MT-13623).

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