This thesis examined whether it is possible to enhance core elements of the information processing system with specific forms of environmental stimulation. The first series of experiments demonstrated that a preweaning environmental enrichment procedure that provided 60 minutes of daily multisensory stimulation accelerated the development of long-term contextual memory and enhanced inhibitory processing in young rats. That is, whilst stimulated and non-stimulated rats exhibited long-term memory of a context at 26 days of age, only stimulated rats showed this ability at 18 days of age. In addition, stimulated rats showed a faster rate of extinction of long-term contextual memory at 21 days of age, which was taken as evidence of enhanced inhibitory learning (i.e., context ??? no US) in these rats. Subsequent experiments with adult rats demonstrated that a combination of preweaning multisensory stimulation and postweaning rearing in an enriched environment improved the (1) specificity of long-term contextual memory, (2) speed of contextual information processing, and (3) availability of attentional resources. More specifically, enriched-reared rats demonstrated superior ability to discriminate between two similar contexts in comparison to standard-reared rats. In addition, enriched-reared rats showed superior memory of a context when there was limited time available to form a memory of that context. This finding was taken to indicate that rats that receive environmental enrichment are able to process contextual information more rapidly. Finally, standard-, but not enriched-, reared rats showed less conditioning to a discrete stimulus when it was presented in combination with a stronger stimulus during training compared to when it was presented by itself. The finding that enriched-reared rats did not show this overshadowing effect suggests that these rats have greater availability of attentional resources to divide between two stimuli that are competing for attention. The experiments with rats were followed by two experiments with children that investigated the effects of a computerised cognitive training procedure on information-processing speed. These experiments demonstrated that 30-minutes per weekday of training in rapid decision-making for three to five weeks improved children???s performance on two tests of processing speed (i.e., a choice reaction time and odd-man-out task). In addition, the speeded training improved children???s ability to sustain their attention and inhibit impulsive responses on a continuous performance test (Test of Variables of Attention). The cognitive training procedure had no effect on children???s performance on a measure of fluid intelligence (Raven???s Standard Progressive Matrices). The results of the experiments reported in this thesis suggest that a number of fundamental cognitive processes can be modified by environmental conditions that place increasing demands on the information-processing system. A neurobiological model, focusing on myelin, axon diameter, and the glutamatergic, glucocorticoid, noradrenergic, and cholinergic systems, was proposed in order to explain the observed effects of environmental stimulation on cognition in children and rats. The rationale for attempting to enhance fundamental cognitive processes was that improving these processes should ultimately improve general intellectual functioning. With respect to this aim, the correlational data from the present experiments with children revealed promising trends towards greater improvements on the tests of fundamental cognitive processes in those children in the training group with slower processing speed at the start of the intervention. This finding suggests that cognitive training may be even more effective at enhancing processing speed and other fundamental cognitive processes in children with intellectual impairments???who reportedly have slower processing speed than normal children. However, the extent to which training-related improvements in fundamental cognitive processes generalise to improvements in general cognitive functioning is unclear. That is, there is insufficient evidence that processing speed and other fundamental cognitive processes are causally related to intelligence. It is therefore essential that future cognitive training research is mindful of related developments within the intelligence and information processing literature.
| Identifer | oai:union.ndltd.org:ADTP/258514 |
| Date | January 2004 |
| Creators | Woodcock, Elizabeth Ann, Psychology, Faculty of Science, UNSW |
| Publisher | Awarded by:University of New South Wales. Psychology |
| Source Sets | Australiasian Digital Theses Program |
| Language | English |
| Detected Language | English |
| Rights | Copyright Elizabeth Ann Woodcock, http://unsworks.unsw.edu.au/copyright |
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