J Steiner

Bio: J Steiner is an academic researcher. The author has an hindex of 1, co-authored 1 publications receiving 18 citations.

Neurophysiology of the Anuran Visual System

Abstract: Due to recent behavioral and electrophysiological data found in different anurans, some investigators believe that the visual system of frogs and toads is a highly specialized machinery which detects only self-moving visual signals relevant to the survival of the animals (p. 357 f., 435 ff.). Other visual signals are believed to be “suppressed” by the neuronal network of the visual system. Thus the ironic poem of Heinrich Heine would be incorrect as such a neuronal machine leaves little possibility for frogs to “erquicken… an Sonnenblicken”. The angular velocity of the sun and the shadows cast by stationary objects in the frog’s habitat would be too slow to be discovered by the movement-detecting neuronal systems.

The Functional Organization of the Brain of the Cuttlefish Sepia officinalis

Abstract: The functional organization of the brain of Sepia has been investigated by electrical stimulation. As a result several new divisions of the brain have been made. The pedal ganglion has been shown to consist of four parts: (1) the anterior chromatophore lobes innervating the skin and muscles of the anterior part of the head and arms; (2) the anterior pedal lobe innervating the arms and tentacles; (3) the posterior pedal lobe innervating the funnel, collar and retractor muscles of the head; (4) the lateral pedal lobes innervating the muscles of the eyes and tissues of the orbits. The palliovisceral (or visceral) ganglion, apart from the magnocellular lobe demonstrated by Young (1939), is shown here to consist of (1) a central palliovisceral lobe innervating the mantle, funnel and viscera; (2) a pair of lobes innervating the muscles of the fins; (3) a pair of posterior chromatophore lobes innervating the muscles of the chromatophores and skin of the mantle, fin and back of the head; (4) a pair of vasomotor lobes. Because of these new divisions the three main groupings of the suboesophageal neural tissue are now referred to as the anterior, middle and posterior suboesophageal masses corresponding to the old brachial, pedal and palliovisceral divisions. The suboesophageal centres are classified as lower motor centres and intermediate motor centres, depending on the kind of response they give to electrical stimulation and their peripheral connexions. In the supraoesophageal lobes, higher motor centres and silent areas are recognized. The silent areas include the vertical, superior frontal, subvertical, precommissural and dorsal basal lobes. Of the higher motor centres the anterior basal lobe is primarily concerned with the positioning of the head, arms and eyes, particularly during movements involving changes in direction while swimming. Such manoeuvres are brought about by the anterior basal lobe control over the fins and position of the funnel. The posterior basal lobe is here shown to consist of six main divisions: (1) the subvertical lobe; (2) the dorsal basal lobes; (3) the precommissural lobe; (4) the medial basal lobe; (5) the lateral basal lobe; (6) the interbasal lobe. The medial, lateral and interbasal lobes are higher motor centres. The lateral and medial basal lobes control movements of the chromatophores and skin; the medial basal lobe controls swimming, breathing, fin movements and various visceral functions. The interbasal lobe controls the movements of the tentacles. The optic nerves and the optic lobes, at their periphery, are electrically inexcitable. Electrical stimulation of the centre of the optic lobes evokes all the responses that can be obtained from the other higher motor centres. The results are discussed in terms of Sanders & Young's (1940) physiological classification of the brain. A further category intermediate motor centre is recognized. Summary lists of the responses of each lobe are given on pages 516, 520, 525.

On the generation of locomotion in the spinal dogfish.

Abstract: 1. If a dogfish is spinalized, the caudal part of the body (65 segments) will exhibit continuous swimming movements at rest. The speed of locomotion can be increased by various exteroceptive stimuli. As an indicator of the CNS activity the EMG activity of different segments along the body has been recorded simultaneously during swimming at different speeds. The two sides of one segment show alternating EMG activity. 2. During forward swimming there is a lag between the activation of rostral and more caudal segments. This lag decreases as the speed of swimming increases (from 0.4–2.7 Hz), but there is a linear relation between the lag and the cycle length, i.e. a phase lag. This phase lag can be shown even between the activation of adjacent segments. It has the same value over the part of the body investigated. During certain exteroceptive stimuli, backwards swimming occurs, i.e. there is a phase lag between caudal and more rostral segments. 3. Red muscle fibres participate alone at lower rates of swimming whereas at faster rates also the dorsal and ventral white longitudinal muscles take part. 4. If the spinal cord is subdivided into smaller parts controlling down to 8 segments, alternating activity can be generated as well as a lag in the activation of different segments. These smaller parts can “swim” both backwards and forwards but their activity is independent of each other. 5. It is concluded that the available data on fish locomotion can be best explained if the swimming is generated by a central network responsible for the alternate activity of the two sides as well as the phase coupling between the segments. This central network would be distributed throughout the spinal cord.

The significance of cerebellar function for a reflex movement of the dogfish

Abstract: An elevation of the pectoral fin generated reflexly by electrical stimulation of the fin was studied in decerebrate dogfish (Scyliorhinus) by recording the electromyogram from the levator muscle. This pectoral fin reflex had two components: a phasic lift of the fin lasting for 70–100 ms, followed by a sustained (tonic) elevation lasting for 500–1,000 ms or more. Ablation of the cerebellum resulted in a pronounced depression of the reflex which particularly affected the tonic component. Division of the brainstem at the level of the obex restored both components to the reflex and frequently led to spread of activity to other muscles. It is suggested that in this animal the brainstem generates a powerful tonic inhibitory drive directed at spinal motor circuits and that the cerebellum modulates precisely this inhibitory influence to permit effective and efficient movement.