The possible meaning of the upper and lower alpha frequency ranges for cognitive and creative tasks

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Abstract

This study is aimed at verifying the functional independence of two frequency bands within the alpha range. It is based on experiments that examined the role of these two bands with regard to the amount of local electrogenesis (amplitude) and the cooperation of brain areas (coherence) in mental tasks concerning: (1) visual perception and imagery; (2) listening to and composing music; (3) verbal and visual creativity; and (4) aspects of mood. In all experiments EEG were recorded for at least 1 min during each task, separated one from another by at rest periods of at least equal lengths. EEG electrodes were pasted according to the 10/20 system (averaged ear lobes as reference). After FFT power was calculated for all 19 electrodes, coherence was estimated for all possible electrode pairs (i.e. 171). This was done for six frequency ranges between 1.5 and 31.5 Hz, the alpha range having been divided into two (7.5–9 Hz and 9.5–12.5 Hz). The spectral parameters obtained during each task were compared with those of the merged EEG at rest, significant changes (P≤0.01–P≤0.05) were entered into schematic maps of the brain. Generally, fewer differences were found for amplitude than for coherence. In all four tasks concerning visual perception the clearest differences were found in single person studies. But also in group studies more or less distinct differences were found between alpha 1 and 2. Also in the series with music the two alpha bands did not behave uniformly, nor were uniform features found in the two series of musically trained and untrained subjects. Distinct discrepancies were also found in a verbal and visual imagery task. With respect to mood, only elevated mood was correlated with a decrease of coherence in alpha 2 and an increase of amplitude in alpha 1. This study though hinting at a different functional significance of these two alpha bands, however, does not allow to draw any conclusions as to their distinct functional meanings. Generally, the long-term coherence changes observed under these different mental tasks support the idea that part of information processing in the brain is reflected by the EEG. Structural peculiarities and microelectrode recordings of the cortex support this conclusion. © 1997 Elsevier Science B.V.

Introduction

It has often been claimed that the subdivision of the EEG into different frequency bands, which goes back to Hans Berger and has its origin in the clinical EEG, is justified also from a functional point of view. However, its alleged uniformity has often been questioned, particularly with regard to the alpha band. Although the problem of its individuality was studied by several authors by means of factor analysis (Herrmann et al., 1980) no unanimous answer to this question has been found so far. Based on structure–analytic reflections several authors recommended a subdivision of the alpha into at least two bands. Since, moreover, several psychological studies also support the idea of a functionally different meaning of higher and lower-frequency alphas (Klimesch et al., 1993), we wanted to know whether differences within the alpha range might also show up in cognition studies with ERP in the on-going EEG. For this purpose two spectral parameters, amplitude and coherence, were used as indices. Klimesch (1996)found that the upper alpha band reflects the retrieving of semantic long-term memory information by determining an `individual alpha peak frequency' for each subject separately. Our study, based on broad frequency bands, therefore, had a priori lower chance to help solving this problem, all the less as our studies were performed mainly on groups and not on individuals. In spite of these drawbacks, our amplitude and coherence studies on cognitive processes brought further evidence that splitting the alpha may allow more insight into the possible functional meaning of the alpha rhythms.

With this aim in mind the ongoing EEG was studied in several sets of experiments. One of them concerned the visual world with contemplating and memorizing pictures, mentally creating images and silently reading, another the world of sounds while listening to and composing music. The third set of experiments concerned eventual correlations between the skill in performing mental tasks and the amount of coherence changes. We called the two frequency bands to be studied alpha 1 and 2; they were arbitrarily defined between 7.5 and 9, and between 9.5 and 12.5 Hz, respectively.

Section snippets

Method

The method used in this study has been developed by us several years ago (Rappelsberger and Petsche, 1988). It compares the values of amplitude and coherence during a mental process with those during the averaged EEG at rest. Since this method is based on EEG epochs of at least 1 min duration, the results represent average values of the changes of these parameters by a mental process. The EEG is recorded from the usual 19 electrodes of the 10/20 system with respect to averaged recordings from

Visual tasks

The first series to be reported concerns visual tasks. The following results are from an experiment on 38 females in which four different visual tasks had to be performed: (1) to contemplate a slide of a painting projected onto the wall; (2) to silently read a text, for distraction; (3) to memorize the painting shown just before; and (4) to mentally create a picture of one's own choice. Each task was performed for 2 min and was repeated with four paintings of different periods of the history of

Discussion

Previous papers on the significance of the alpha relate almost exclusively on amplitude. Apart from the initial idea that alpha is related to attention, Wertheim (1981)was among the first to claim that alpha depends on oculomotor functioning rather than on the quality of perception; this means that alpha blocking would be due to visual activity involving retinal feedback (Shaw, 1992). If this hypothesis were correct, differences in the degree of alpha blocking should be expected between the

Acknowledgements

This work was supported by the Austrian Fonds zur Förderung der wissenschaftlichen Forschung, Project S 49-02.

References (33)

  • Berger, H. (1929) Über das Elektrenkephalogramm des Menschen. Arch. Psychiatr. Nervenkr., 87:...
  • Braitenberg, V. (1978) Cortical architectonics: general and areal. In: M.A.B. Brazier and H. Petsche (Eds.),...
  • Braitenberg, V. and Schüz, A. (1991) Anatomy of the Cortex: Statistics and Geometry. Springer,...
  • Damasio, A.R. (1990) Synchronous activation in multiple cortical regions: a mechanism for recall. Semin. Neurosci., 2:...
  • Dinse, H.R., Akhavan, A.C., Krüger, K., Spengler, F. and Schreiner, C.E. (1994) Low-frequency oscillations of visual,...
  • Gevins, A.S. (1981) The use of brain electrical potentials (BEP) to study localization of human brain function. Int. J....
  • Hari, R. (1994) Characterization of magnetoencephalographic 10- and 20 Hz rhythms. In: E. Basar (Ed.), Alpha-activity:...
  • Herrmann, W.M., Fichte, K. and Kubicki, St. (1980) Definition von EEG-Frequenzbändern aufgrund strukturanalytischer...
  • Klimesch, W. (1996) Memory processes, brain oscillations and EEG synchronization. Int. J. Psychophysiol. 24:...
  • Klimesch, W., Schimke, H., Ladurner, G. and Pfurtscheller, G. (1990) Alpha frequency and memory performance....
  • Klimesch, W., Schimke, H. and Pfurtscheller, G. (1993) Alpha frequency, cognitive load and memory performance. Brain...
  • Lindner, K., Petsche, H., Rappelsberger, P. and Schmidt, E. (1989) Denkstrategien beim Kopfrechnen:...
  • Machleidt, W., Gutjahr, L. and Hinrichs, H. (1994) Die EEG-Spektralmuster der Grundgefühle: Hunger, Angst, Aggression,...
  • Martinson, D.M. (1939) A study of brain potentials during mental blocking. J. Exp. Psychol., 24:...
  • Mulholland, T.B. (1972) Occipital alpha revisited. Pschol. Bull., 78:...
  • Osaka, M. (1984) Peak alpha frequency during a mental task: task difficulty and hemispheric differences....
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