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JOSEPH GRADER, MD; GRANT L. HELLER, MD

Arch Ophthalmol. 1964;72(6):763-768.

	Since this article does not have an abstract, we have provided the first 150 words of the full text PDF and any section headings.

Berger in 1929 discovered what is now known as the a rhythm of the brain. This consists of oscillations of electrical potential at a frequency of 8 to 12 per second and is best developed in the parieto-occipital region. This rhythm is best demonstrated with the eyes closed, and may be blocked by the subject's attention to vision with the eyes opened or closed.

By flickering lights the a rhythm may be affected in one of three ways. First, a blocking may occur, in which case the a rhythm disappears. Second, photic driving may occur in which case the a waves of 8 to 12 per second are replaced by waves of the same frequency as that of the flashing light. Third, in some normal and some abnormal subjects nothing happens.

Fig 1 demonstrates blocking and photic driving in a normal patient. With the onset of photic stimulation at . . . [Full Text PDF of this Article]

Author Affiliations
Cleveland

From the Department of Ophthalmology (Dr. Grader) and the Department of Neurology (Dr. Heller), Mount Sinai Hospital.

Footnotes
Read before the Cleveland Ophthalmological Club, Nov 12, 1963.

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