Some problems of occipital alpha block in man.

Abstract (1) Experiments were carried out in 10 human subjects to try to evaluate the relative importance of visual attentiveness, a patterned visual input, oculomotor control functions and mental effort with respect to attenuation of the occipital alpha rhythm. (2) Alpha rhythm was almost completely blocked when alert subjects were involved in reading even when the near triad of accommodation had been experimentally eliminated or minimized. Thus ‘visual attentiveness’ alone is sufficient to block the alpha rhythm. (3) Visual sensory detail alone was not a sufficient stimulus to block the alpha rhythm, even though accompanied by saccadic movements. Rather it is the attentiveness to the detail which blocks the alpha rhythm. (4) Progressively more difficult mental effort, as in serial multiplication, eventually led to an attenuation of the alpha rhythm. A sustained type of mental effort such as blindfold chess led to an initial attenuation of the alpha rhythm followed by a gradual return after the first few minutes of play to resting eyes closed levels. However, during periods in which subjects claimed that they required exceptional increases in mental effort, the alpha rhythm again became attenuated. The possible significance of alpha block is discussed.

[1]  D B Lindsley,et al.  Effect upon the EEG of acute injury to the brain stem activating system. , 1949, Electroencephalography and clinical neurophysiology.

[2]  J. Shaw,et al.  EXPERIMENTAL ENHANCEMENT OF ALPHA ACTIVITY. , 1965, Electroencephalography and clinical neurophysiology.

[3]  A. Glass.  MENTAL ARITHMETIC AND BLOCKING OF THE OCCIPITAL ALPHA RHYTHM. , 1964, Electroencephalography and clinical neurophysiology.

[4]  R. Chapman,et al.  A quantitative survey of kappa and alpha EEG activity. , 1962, Electroencephalography and clinical neurophysiology.

[5]  A. Mundy-castle,et al.  The electroencephalogram and mental activity. , 1957, Electroencephalography and clinical neurophysiology.

[6]  G. Durup,et al.  I. L'électrencéphalogramme de l'homme. Observations psycho-physiologiques relatives à l'action des stimuli visuels et auditifs , 1935 .

[7]  D. Lindsley.  Psychological phenomena and the electroencephalogram. , 1952, Electroencephalography and clinical neurophysiology.

[8]  Chester W. Darrow,et al.  Eye movements, EEG, GSR and EKG during mental multiplication ☆ , 1962 .

[9]  H. Jasper.  CORTICAL EXCITATORY STATE AND SYNCHRONISM IN THE CONTROL OF BIOELECTRIC AUTONOMOUS RHYTHMS , 1936 .

[10]  E. Adrian,et al.  THE BERGER RHYTHM: POTENTIAL CHANGES FROM THE OCCIPITAL LOBES IN MAN , 1934 .

[11]  G. Moruzzi,et al.  Brain stem reticular formation and activation of the EEG. , 1949, Electroencephalography and clinical neurophysiology.

[12]  J. R. Lee,et al.  How Does the Striate Cortex Begin the Reconstruction of the Visual World? , 1971, Science.

[13]  H. Jasper,et al.  INTRACELLULAR OSCILLATORY RHYTHMS IN PYRAMIDAL TRACT NEURONES IN THE CAT. , 1965, Electroencephalography and clinical neurophysiology.

[14]  T. Mulholland,et al.  An Unexpected Artefact in the Human Electroencephalogram Concerning the Alpha Rhythm and the Orientation of the Eyes , 1965, Nature.

[15]  T. Mulholland,et al.  Oculomotor Function and the Alpha Activation Cycle , 1966, Nature.

[16]  S. Andersson,et al.  Physiological basis of the alpha rhythm , 1968 .