EEG-alpha rhythms and memory processes
Section snippets
Introduction: memory search and the possible meaning of thalamo–cortical feedback loops
One of the crucial issues in memory research is based on the question of how a search process finds the relevant information in memory. Whereas most researchers would agree that (parts of) the cortical neural network can be considered a storage network for memory, little is known about the way a search process is initiated and how information is accessed and retrieved. Memory theories assume that a search process can be described as a spreading activation process in the cortical storage network
Interindividual differences in alpha frequency and memory performance
In a first step, before testing this prediction in detail, it is important to show whether alpha frequency does vary interindividually and what the factors are that affect alpha frequency. It is well known that alpha frequency decreases with increasing age. Köpruner et al. (1984) have found a linear relationship (alpha peak frequency=11.95–0.053× age) within the age range of adult subjects that is depicted in Fig. 2.
According to this relationship, a young adult of, e.g. 20 years has an expected
Intraindividual differences in alpha frequency and memory performance
Although Experiments 1 and 2 support the hypothesis of a relationship between alpha frequency and memory performance, the results, reported so far, could theoretically also be explained in terms of interindividual differences in attention. It could be objected that the higher IAF of good memory performers reflects a state of increased attention which is responsible for an increase in memory performance. There is ample evidence that alpha desynchronization may reflect attention (Mulholland, 1969
Shifts in alpha power and memory performance
Amplitude analyses in an individually defined lower and upper alpha band will be an important additional measure for studying cognitive processes and memory in particular. Topographical as well as interindividual differences in EEG power are very large. Thus, an adequate way of measuring event-related shifts in EEG power should not be based on absolute but instead on relative differences as was first proposed by Pfurtscheller and Aranibar (1977) who have coined the term `event-related
Discussion
The most general conclusion is that alpha frequency is a sensitive measure for cognitive performance or cognitive processing capacity. Alpha frequency varies inter- and intraindividually as a function of processing capacity. The decrease in alpha frequency with increasing age and the lowered alpha frequency as a result of a variety of neurological disorders are well-known examples underlining the validity of a general relationship between alpha activity and cognitive performance.
Memory and
Acknowledgements
This research was supported by the Austrian `Fonds zur Förderung der wissenschaftlichen Forschung', Project P-10235.
References (33)
- Basar, E. (1992) Brain natural frequencies are causal factors for resonances and induced rhythms. In: E. Basar and T....
- Earle, J.B. (1988) Task difficulty and EEG alpha asymmetry: an amplitude and frequency analysis. Neuropsychobiology,...
- Evans, C.R. and Mulholland, T.B. (Eds.) (1969) Attention in Neurophysiology. Butterworths,...
- Höhl-Abrahao, J.C. and Creutzfeldt, O.D. (1991) Topographical mapping of the thalamocortical projections in rodents and...
- Klimesch, W. (1994) The structure of long-term memory: a connectivity model of semantic processing. Lawrence Erlbaum,...
- Klimesch, W., Schimke, H. and Ladurner, G. (1988) Die Suchzeit für episodische und semantische Information. Sprache...
- Klimesch, W., Schimke, H., Ladurner, G., and Pfurtscheller, G. (1990) Alpha frequency and memory performance. J....
- Klimesch, W., Pfurtscheller, G. and Schimke, H. (1992): Pre- and poststimulus processes in category judgement tasks as...
- Klimesch, W., Schimke, H. and Pfurtscheller, G. (1993) Alpha frequency, cognitive load and memory performance. Brain...
- Klimesch, W., Schimke, H. and Schwaiger, J. (1994) Episodic and semantic memory: an analysis in the theta and alpha...
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