Limit cycle oscillations of the human eye

Scotto, Maria; Oliva, Giulia Anna

doi:10.1007/bf00336185

Cited by 6 publications

(1 citation statement)

References 58 publications

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“…Real negative feedback systems, however, may become unstable if they contain phase-shifting elements (delays, filters), and if the closed loop gain is greater than unity at frequencies where the phase lag (<f>) of the feedback signal is ^ ^ 2tu (Nyquist criterion, see textbooks of feedback control). Hence, for optimal performance, the feedback gain must be limited according to the system's delay (Kupfmuller 1974;Scotto & Oliva 1984). Thus the properties of the real system define an upper boundary of .performance.…”

Section: (I) Stability Of the Control Systemmentioning

confidence: 99%

Compensatory head roll in the blowflyCalliphoraduring flight

Hengstenberg

Sandeman

Hengstenberg

1986

Proc. R. Soc. Lond. B.

210

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Video records were made of the blowfly Calliphora erythrocephala L. mainly during tethered flight in a wind-tunnel, to study its movements about the longitudinal body axis (roll). During undisturbed flight, flies hold their head on average aligned with the body but may turn it about all three body axes. Pitch and yaw turns of the head are comparatively small (20°), whereas roll turns can be large (90°), and fast (1200° s -1 ). When passively rolled, flies produce compensatory head movements during walking or flight; at rest this reflex is turned off. Flies perceive a static misalignment relative to the vertical, as well as roll motion up to 10000° s -1 . Within this range flies counteract an imposed roll with maximal gain at about 1000° s -1 . Compensatory head movements are made with very low latency (down to ∆t ≈ 5ms), and with considerable speed (up to ω = 1000° s -1 ). Flies may ‘disregard’ an apparent deviation from their correct orientation, and may superimpose spontaneous head movements on those elicited by a stimulus. Compensatory head movements generally undercompensate the imposed misalignment. Simultaneously, however, flies modify their wing pitch and wingbeat amplitude to produce a compensatory roll torque. Since head and body roll act simultaneously and in the same direction, the overall speed and degree of head realignment, relative to external coordinates, increase considerably. This is certainly an advantage for flight in turbulent air. In still air, without need to correct an imposed misalignment, flies nevertheless produce spontaneous fluctuations of their flight torque, and head roll movements in the opposite direction. This is to be expected if flies intend to keep their eyes aligned with the coordinates of the environment while spontaneously performing banked turns. The limits of fly vision and the advantages of compensatory head movements for different visually guided behaviour are discussed. Compensatory head roll movements give flies greater manoeuvrability when cruising than the visual system would allow, without such a stabilizing reflex.

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Section: (I) Stability Of the Control Systemmentioning

confidence: 99%

Compensatory head roll in the blowflyCalliphoraduring flight

Hengstenberg

Sandeman

Hengstenberg

1986

Proc. R. Soc. Lond. B.

210

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Exploring the Role of the Basal Ganglia in Motor Control Using Experimental Results and Mathematical Modeling

Beuter

1994

Advances in Behavioral Biology

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Ocular limit cycles induced by delayed retinal feedback

et al. 1993

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Lisberger's and Robinson's models of smooth pursuit predict very different results from altering retinal feedback delay. We have therefore investigated the effects of increasing the retinal feedback time delay in three normal human subjects by means of an artificial feedback paradigm. When additional delays were incorporated into the retinal feedback path a threshold was reached beyond which the eye exhibited sustained self-excited oscillations or "limit cycles". The oscillation period increased linearly (as the added delay was increased) with slopes ranging from 1.41 to 1.6 with zero-delay intercepts of between 212 and 306 ms. Contrary to our experimental findings the Robinson and Lisberger models predict that the plot of oscillation period against added delay should have a slope of 3.4 and 2.7 and an intercept of 479 and 554 ms, respectively. Neither model produced comparable limit cycles, both being unstable at delays greater than 280 ms. Our results imply that the models of smooth pursuit need to incorporate predictive control.

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Limit cycle oscillations of the human eye

Cited by 6 publications

References 58 publications

Compensatory head roll in the blowflyCalliphoraduring flight

Compensatory head roll in the blowflyCalliphoraduring flight

Exploring the Role of the Basal Ganglia in Motor Control Using Experimental Results and Mathematical Modeling

Ocular limit cycles induced by delayed retinal feedback

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