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Abstract

Horizontal rotational head movements were video-taped from pigeons standing freely in a rotating cylinder. The cylinder carried vertically striped
patterns approximating a sinusoidally modulated horizontal intensity distribution. We altered systematically various stimulus parameters: spatial wavelength and
contrast of the pattern, angular velocity of the pattern motion and mode of motion onset. We found: (1) both gradual acceleration of the patterned cylinder as well as
immediate onset of pattern motion elicit the sequence of smooth following and saccadic resetting movement typical of the rotational ''stare'' head nystagmus; (2) in
experiments with rapid onset of pattern motion, velocity of the smooth following response gradually increases to its steady-state level over a period of about 10 sec;
(3) the saccadic head rotations are not stereotyped: larger and shorter saccades follow in an irregular sequence, saccadic velocity and average size varies with
stimulus conditions; (4) in the range of 0.9-95 deg/sec, the velocity of the following phase increases in parallel with stimulus speed; (5) in the range of spatial
wavelengths of the striped patterns from 6 to 45 deg, at a given drum velocity, patterns of short wavelengths elicit optokinetic head rotations with higher gain (head
velocity/drum velocity) than patterns of long wavelengths; (6) response velocity increases with pattern contrast (Michaelson contrast 5, 32 and 75), following
approximately a logarithmic relation; (7) our results on rotational optokinetic head movements support the notion that the neural mechanism underlying motion
detection operates like a correlation mechanism. Copyright (C) 1996 Elsevier Science Ltd.