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Biomedical subjects

A F Fuchs

Publications and source records attributed to A F Fuchs.

102 records · Page 6Linked to original sources
PubMed1971

Development of isometric tension in simian extraocular muscle.

1. Isometric tension resulting from electrical stimulation of the abducens nerve was measured in the lateral rectus muscle of anaesthetized monkeys.2. The lateral rectus showed no increase in maximum tension at stimulus frequencies greater than 400/sec.3. However, at frequencies between 400 and 600/sec, the rate of change of tension increased so that maximum tension was achieved more rapidly.4. Rates greater than 600/sec caused no further increases in the rate of change of tension and actually resulted in a decrease of maximum tension.5. Since, in addition, single fibre recordings from ocular motor nerves reveal maximum discharge rates of less than 600/sec, units in the abducens nucleus that fire at greater than 600/sec are likely interneurones.6. Stimulation at rates of 30/sec, the frequency at which feline slow or slow twitch fibres produce fused contraction, produced no measurable tonic component of tension. Therefore, the force contributed by slow muscle fibres probably plays an insignificant role during eye movements.

Abducens Nerve↗
PubMed1969

Extraocular muscle afferents to the cerebellum of the cat.

1. Afferents from the extraocular muscles to the cerebellum of the cat were investigated by evoked potential techniques using muscle stretch as a stimulus.2. Short (about 4 msec) latency responses occurred in the vermian folia anterior (Larsell's lobule V b, c) and posterior (lobules VI and VII) to the primary fissure under light Nembutal anaesthesia.3. The location of the cerebellar eye muscle responses coincides with the visual and auditory projections as well as homologous projections from cortical Areas 8 (the frontal eye fields) and 17 in the monkey. It also overlaps the oculomotor area of the cerebellum as revealed by electrical stimulation.4. Facts 2 and 3 above, together with the selective disturbance of saccadic eye movements in humans with cerebellar atrophy, suggest a cerebellum mediated proprioceptive feed-back loop for the control of saccadic eye movements.

Animals↗
PubMed1967

Saccadic and smooth pursuit eye movements in the monkey.

1. Voluntary eye movements were measured in the chronic, unanaesthetized monkey. A training technique is described which conditions the animals to follow a large variety of target trajectories.2. The eye movements of the monkey are not qualitatively different from those of man. In response to random target motions the monkey also employs a combination of saccadic and smooth pursuit movements.3. Monkeys execute their saccades more rapidly than humans.4. Monkeys are capable of attaining smooth pursuit velocities which are twice as fast as those of man.5. Most of the critical experiments showing the separate nature of the saccadic and smooth pursuit modes in man have been performed on monkeys with similar results.6. Therefore, if one remains aware of the quantitative differences between the two primates, results of neurophysiological studies of the occulomotor system of the monkey can be expected to have considerable relevance when extrapolated to man.

Animals↗
PubMed1967

Periodic eye tracking in the monkey.

1. Eye movements were measured in monkeys trained for visual tracking.2. In response to periodic square wave target movements, monkeys do not show a significant reduction in the latency of saccadic movements.3. Under similar conditions, human beings subconsciously reduce their latency and after several cycles are in step with the target.4. In response to sinusoidal targets, monkeys show a latency or phase lag which increases monotonically with frequency starting at 0.3 c/s. Human beings can remain in phase with the target at frequencies up to 1.0 c/s.5. Hence, monkeys do not exhibit the human predictive tracking response.

Journal Article↗