2000 Special IssueTowards a network theory of cognition
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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