The human operator as a servo system element

McRuer, Duane T.; Krendel, Ezra S.

doi:10.1016/0016-0032(59)90072-9

Cited by 125 publications

(32 citation statements)

References 13 publications

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“…Similar predictive phenomena have been demonstrated, with the frequency response method, in the vergence system for binocular fixation (Zuber, 1965) as well as in the accommodation control mechanism of the ocular lens (Stark, Takahashi & Zames, 1965). An analogous predictive effect is known in manual control (McRuer & Krendel, 1959;Stark, lida & Willis, 1961). Prediction was not, however, found in the human pupillary system (Stark, 1968).…”

Section: Introductionmentioning

confidence: 76%

On the predictive control of foveal eye tracking and slow phases of optokinetic and vestibular nystagmus.

Yasui¹,

Young²

1984

The Journal of Physiology

192

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SUMMARY1. Smooth pursuit and saccadic components of foveal visual tracking as well as more involuntary ocular movements of optokinetic (o.k.n.) and vestibular nystagmus slow phase components were investigated in man, with particular attention given to their possible input-adaptive or predictive behaviour.2. Each component in question was isolated from the eye movement records through a computer-aided procedure. The frequency response method was used with sinusoidal (predictable) and pseudo-random (unpredictable) stimuli.3. When the target motion was pseudo-random, the frequency response of pursuit eye movements revealed a large phase lead (up to about 900) at low stimulus frequencies. It is possible to interpret this result as a predictive effect, even though the stimulation was pseudo-random and thus 'unpredictable'.4. The pseudo-random-input frequency response intrinsic to the saccadic system was estimated in an indirect way from the pursuit and composite (pursuit + saccade) frequency response data. The result was fitted well by a servo-mechanism model, which has a simple anticipatory mechanism to compensate for the inherent neuromuscular saccadic delay by utilizing the retinal slip velocity signal.5. The o.k.n. slow phase also exhibited a predictive effect with sinusoidal inputs; however, pseudo-random stimuli did not produce such phase lead as found in the pursuit case.6. The vestibular nystagmus slow phase showed no noticeable sign of prediction in the frequency range examined (0 -0 7 Hz), in contrast to the results of the visually driven eye movements (i.e. saccade, pursuit and o.k.n. slow phase) at comparable stimulus frequencies.

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Section: Introductionmentioning

confidence: 76%

On the predictive control of foveal eye tracking and slow phases of optokinetic and vestibular nystagmus.

Yasui¹,

Young²

1984

The Journal of Physiology

192

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“…The angle and IEMG signals were subjected to cross correlational and spectral analysis25 26 to quantify the resting and action tonic stretch reflexes. This analysis allows stretch evoked muscle activity at the stretching frequencies to be distinguished from other activity unrelated to the stretch.…”

Section: Methodsmentioning

confidence: 99%

Does spasticity contribute to walking dysfunction after stroke?

Ada

Vattanasilp

O’Dwyer

et al. 1998

Journal of Neurology, Neurosurgery & Psychiatry

116

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Objectives-Clinically, it is assumed that spasticity of the calf muscles interferes with walking after stroke. The aim was to examine this assumption by evaluating the contribution of spasticity in the gastrocnemius muscle to walking dysfunction in an ambulant stroke population several months after stroke. Methods-Fourteen stroke patients who were able to walk independently and 15 neurologically normal control subjects were recruited. Both resting and action stretch reflexes of the gastrocnemius muscle were investigated under conditions that simulated walking. Resting tonic stretch reflexes were measured to assess spasticity whereas action tonic stretch reflexes were measured to assess the possible contribution of spasticity to gait dysfunction. Results-Two thirds of the stroke patients exhibited resting tonic stretch reflexes which indicate spasticity, whereas none of the control subjects did. However, the stroke patients exhibited action tonic stretch reflexes that were of similar magnitude to the control subjects, suggesting that their reflex activity during walking was not diVerent from that of control subjects. Furthermore, there was no evidence that the action stretch reflex in the stroke patients contributed a higher resistance to stretch than the control subjects. Conclusions-Whereas most of the stroke patients exhibited spasticity when measured both clinically and physiologically, they did not exhibit an increase in resistance to dorsiflexion due to exaggerated action tonic stretch reflexes. It is concluded that it is unlikely that spasticity causes problems in walking after stroke in ambulant patients. Therefore, it seems inappropriate to routinely reduce or inhibit the reflex response to improve functional movement in stroke rehabilitation. Factors other than spasticity should be considered when analysing walking after stroke, so that appropriate treatment is provided to patients. (J Neurol Neurosurg Psychiatry 1998;64:628-635)

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“…In the United Kingdom, Bartlett directed work at what would become the Medical Research Council Applied Psychology Unit in Cambridge. During World War II, Paul Fitts led the development of "engineering psychology" in the United States, and engineers such as McRuer andKrendel (1959/2005) followed up the wartime interest in manual control to make massive contributions to modeling mathematically the manual control of complex systems. Strong groups developed in Germany, the Netherlands, France, and, later, Japan.…”

Section: June 2008 -Human Factorsmentioning

confidence: 99%