Sigma‐movement and Sigma‐nystagmus: A New Tool to Investigate the Gaze‐pursuit System and Visual‐movement Perception in Man and Monkey*

The emulation theory of representation: Motor control, imagery, and perception

“…How the brain predicts reafference is a fascinating problem that spans motor control (Miall & Wolpert 1996), sensory physiology (Adler et al 1981;Blakemore et al 2001;Haarmeier et al 1997), neuroethology (Bell et al 1983;, and even psychiatry, where it is postulated that a perturbation of the CDEC system may underlie the positive symptoms of schizophrenia (Blakemore et al 2002;Feinberg 1978). It has been postulated that one way to solve this problem would be to have an emulator that specifically modelled the expected reafference of every motor command and then compared the output with the sensory inflow.…”

Gaze stabilization in the primate

“…Sigma-OKN can also be induced in monkeys when the stroboscopically illuminated periodic visual pattern is presented during postrotatory nystagmus or OKAN (Grtisser et al 1979). Sigma-OKN can reach velocities of up to 90°.s -1 and is followed in darkness by sigma-OKAN (Adler et al 1981). The angular velocity of the sigma-OKN increases with the period of the stationary stimulus pattern and the flash frequency.…”

The psychophysics of the pursuit oculomotor system

“…The repeating identical targets give only an ambiguous motion signal if the smooth pursuit movement is disturbed. By presenting a sequence of flashes whose timing was modified with Gaussian noise, Adler et al (1981) found that with a coefficient of variation (standard deviation/mean interval) of more than 0.36, smooth eye movements and the picket-fence illusion broke down.…”