Graduation Year

12-1992

Document Type

Thesis

Degree

Master of Science

Degree Name

Master of Science (M.S.)

Department

Biology

Degree Granting Department

Biology

Major Professor

Steward Swihart, Ph.D.

Committee Member

Gary Arendash, Ph.D.

Committee Member

Frank Friedl, Ph.D.

Committee Member

Paschal Strong, Ph.D.

Abstract

Electrical potentials were recorded from scalp of normal male subjects while they were viewing continuously moving sinusoidal gratings. Responses from the occipital cortex were amplified, digitized, stored and then transformed from the time domain to the frequency domain using a microcomputer based Fast Fourier Transform algorithm. High frequency components (Beta Activity) of the resulting power spectrum were analyzed for evidence on neural generators (electrical sources) in the striate cortex driven presumably by transient-cells (Y-cells or Magnocellular) responding to the continuously moving grating. Several stimulus parameters were examined: angular velocity, spatial frequency, direction (orientation), color, and intensity. A16 Hz component of the power spectrum associated with motion detection manifested at the cortical level was identified, Motion Evoked Potentials (MEPs). Statistical analyses revealed that responses were dependent on the angular velocity of the stimulus, the airection of motion, and the particular color of the stimulus, but not on spatial frequency or stimulus intensity.

Three physiological explanations of the results are discussed: (1) cortico-thalamo-cortical reverberatory circuits, (2) intrathalamic or intracortical reverberatory circuits, and (3) after discharges of local neurons. It was concluded that an intracortical reverberatory circuit is the most likely neuronal generator of the Motion Evoked Response and that the amplitude of the response is dependent on angular velocity.

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