Is the alpha rhythm a control parameter for brain responses? |
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Authors: | Erol Bas¸ar Juliana Yordanova Vasil Kolev Canan Bas¸ar-Eroglu |
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Institution: | (1) Institute of Physiology, Medical University of Lübeck, D-23538 Lübeck, Germany, DE;(2) Institute of Physiology, Bulgarian Academy of Sciences, BG-1113 Sofia, Bulgaria, BG;(3) Institute of Psychology and Cognition Research, University of Bremen, Bremen, Germany, DE;(4) Brain Dynamics Research Unit, TüBITAK, Ankara, Turkey, TR |
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Abstract: | The main goal of the present study is to develop a conceptual analysis of alpha response in the brain based on single sweep
evaluation. A new method was employed to estimate a set of single-sweep parameters and quantify the oscillatory behaviour
of single, electroencephalograph (EEG) sweeps. It was aimed to demonstrate that brain alpha responses are governed by spontaneous
alpha activity and to validate the principle of brain response excitability. Because the spontaneous alpha activity depends
on both the topology of recording and the subject’s age, topology and age models were used. Spontaneous and evoked alpha activity
were recorded at frontal and occipital sites in three groups of subjects: 3-year-old children, young adults and middle-aged
subjects. Amplitude, enhancement and phase-locking of single alpha responses to visual stimuli were analysed. Major results
showed that: (1) visual alpha responses could be recorded only if the alpha rhythm was developed in the spontaneous EEG independent
of electrode location; (2) middle-aged adults showed more expressed frontal spontaneous alpha activity in comparison with
young adults; (3) accordingly, alpha responses with higher amplitude and stronger phase-locking were produced over the frontal
brain area in middleaged than young adults. These results validate the principle of brain response excitability and demonstrate
that a shift towards frontal brain areas for both the spontaneous and evoked alpha activity occurs with increasing age in
adults. The results are discussed in the context of the diffuse and distributed alpha system of the brain. Age-dependent changes
in frontal alpha activity are suggested to be related to frontal brain functioning during aging.
Received: 6 November 1995 / Accepted in revised form: 13 March 1997 |
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