Lateral Turns Research Articles

EPV 16. Spatial orientation deficit in a rat model of acute bilateral vestibulopathy

Background and aim Characterisation of the spatial orientation and locomotion behaviour after bilateral vestibular labyrinthectomy in the rat. Methods Ten Sprague-Dawley rats underwent a bilateral labyrinthectomy (BL) by transtympanic injection of bupivacaine and arsenilate, 10 rats received a bilateral middle-ear injection of saline (sham) as a control group. Behavioural testing was performed 1 day before and at days 1, 2, 3, 7, 15, 30 and 60 after BL/sham injection as follows: (1) analysis of spatial exploration behaviour in a square open field by the Noldus EthoVision System; (2) quantitative analysis of locomotion pattern by the Noldus CatWalk System. Results At all time points, rats of the sham group showed a strategically distributed exploration pattern with a preferred movement along the lateral edges and a preferred position in the corners of the open field. The exploration behaviour was guided by head movements in the lateral direction. In contrast, rats of the BL group presented with a omnidirectional exploration strategy and stayed in the central parts of the open field significantly longer. This exploration pattern did not change over time. Lateral head and body turns were reduced relative to controls. Mean velocity during exploration in the open field was significantly higher in the BL than in the sham group until day 60, whereas mean velocity during CatWalk measurement adapted between groups after day 15 post BL/sham injection. Conclusions A bilateral vestibular lesion induces a persistent deficit in spatial exploration behaviour. The pathophysiological basis seems to be a disturbance of head direction cells in the hippocampal formation due to the lack of vestibular input.

Random walks on the mental number line

The direction of influence between conceptual and motor activation, and its relevance for real-life activities, is still unclear. Here, we use the frequently reported association between small/large numbers and left/right space to investigate this issue during walking. We asked healthy adults to generate random numbers as they made lateral turns and found that (1) lateral turn decisions are predicted by the last few numbers generated prior to turning; (2) the intention to turn left/right makes small/large numbers more accessible; and (3) magnitude but not order of auditorily presented numbers influences the listener's turn selection. Our findings document a bidirectional influence between conceptual and motor activation and point to a hierarchically organized conceptual-motor activation.

Towards development of a slider-crank centered self-propelled dolphin robot

This paper is devoted to the mechatronic design and implementation of a dolphin-like robot capable of fast swimming. In the context of multiple coordinated control surfaces, a set of serially connected flapping modules is responsible for dorsoventral oscillations, an internal moving slider for pitch control and a yaw joint for lateral turns. To improve the swimming speed, an updated modular slider-crank-based flapping mechanism that fully capitalizes on the continuous high-speed rotation of the DC motor is proposed and constructed. With the proposed mechanisms, the resulting dolphin robot achieved a high level of propulsive speed, largely illustrating the validity of the present design scheme.

Responses of Reticulospinal Neurons in the Lamprey to Lateral Turns

When swimming, the lamprey maintains a definite orientation of its body in the vertical planes, in relation to the gravity vector, as the result of postural vestibular reflexes. Do the vestibular-driven mechanisms also play a role in the control of the direction of swimming in the horizontal (yaw) plane, in which the gravity cannot be used as a reference direction? In the present study, we addressed this question by recording responses to lateral turns in reticulospinal (RS) neurons mediating vestibulospinal reflexes. In intact lampreys, the activity of axons of RS neurons was recorded in the spinal cord by implanted electrodes. Vestibular stimulation was performed by periodical turns of the animal in the yaw plane (60 degrees peak to peak). It was found that the majority of responding RS neurons were activated by the contralateral turn. By removing one labyrinth, we found that yaw responses in RS neurons were driven mainly by input from the contralateral labyrinth. We suggest that these neurons, when activated by the contralateral turn, will elicit the ipsilateral turn and thus will compensate for perturbations of the rectilinear swimming caused by external factors. It is also known that unilateral eye illumination elicits a contralateral turn in the yaw plane (negative phototaxis). We found that a portion of RS neurons were activated by the contralateral eye illumination. By eliciting an ipsilateral turn, these neurons could mediate the negative phototaxis.

Mechanisms for lateral turns in lamprey in response to descending unilateral commands: a modeling study.

Straight locomotion in the lamprey is, at the segmental level, characterized by alternating bursts of motor activity with equal duration and spike frequency on the left and the right sides of the body. Lateral turns are characterized by three main changes in this pattern: (1) in the turn cycle, the spike frequency, burst duration, and burst proportion (burst duration/cycle duration) increase on the turning side; (2) the cycle duration increases in both the turn cycle and the succeeding cycle; and (3) in the cycle succeeding the turn cycle, the burst duration increases on the non-turning side (rebound). We investigated mechanisms for the generation of turns in single-segment models of the lamprey locomotor spinal network. Activation of crossing inhibitory neurons proved a sufficient mechanism to explain all three changes in the locomotor rhythm during a fictive turn. Increased activation of these cells inhibits the activity of the opposite side during the prolonged burst of the turn cycle, and slows down the locomotor rhythm. Secondly, this activation of the crossing inhibitory neurons is accompanied by an increased calcium influx into the cells. This gives a suppressed activity on the turning side and a contralateral rebound after the turn, through activation of calcium-dependent potassium channels.

Lateral turns in the Lamprey. I. Patterns of motoneuron activity.

The activity of motoneurons during lateral turns was studied in a lower vertebrate, the lamprey, to investigate how a supraspinal command for the change of direction during locomotion is transmitted from the brain stem and integrated with the activity of the spinal locomotor pattern generator. Three types of experiments were performed. 1) The muscular activity during lateral turns in freely swimming adult lampreys was recorded by electromyography (EMG). It was characterized by increased cycle duration and increased duration, intensity, and cycle proportion of the bursts on the side toward which the animal turns. 2) Electrical stimulation of the skin on one side of the head in a head-spinal cord preparation of the lamprey during fictive locomotion elicited asymmetric ventral root burst activity with similar characteristics as observed in the EMG of intact lampreys during lateral turns. The cycle duration and ventral root burst intensity, duration, and cycle proportion on the side of the spinal cord contralateral to the stimulus were increased; hence a fictive lateral turn away from the stimulus could be produced. The fictive turn propagated caudally with decreasing amplitude. The increase in burst duration during the turn correlated well with the increase in cycle duration, while changes in contralateral burst intensity and burst duration did not co-vary. Turning responses varied depending on the timing (phase) of the skin stimulation: stimuli in the first two-thirds of a cycle evoked a turn in the same cycle, whereas stimuli in the last third gave a turn in the following cycle. The largest turns were evoked by stimuli in the first third of a cycle. 3) Fictive turns were abolished after transection of the trigeminal nerve or a rhombencephalic midline split, but not in a rhombencephalic preparation with transected cerebellar commissure. High spinal hemisection was sufficient to block turning toward the lesioned side, while turns toward the intact side remained. Taken together these findings suggest that the reticulospinal turn command is essentially unilateral and generated in the rhombencephalon.

Lateral turns in the Lamprey. II. Activity of reticulospinal neurons during the generation of fictive turns.

We studied the neural correlates of turning movements during fictive locomotion in a lamprey in vitro brain-spinal cord preparation. Electrical stimulation of the skin on one side of the head was used to evoke fictive turns. Intracellular recordings were performed from reticulospinal cells in the middle (MRRN) and posterior (PRRN) rhombencephalic reticular nuclei, and from Mauthner cells, to characterize the pattern of activity in these cell groups, and their possible functional role for the generation of turns. All recorded reticulospinal neurons modified their activity during turns. Many cells in both the rostral and the caudal MRRN, and Mauthner cells, were strongly excited during turning. The level of activity of cells in rostral PRRN was lower, while the lowest degree of activation was found in cells in caudal PRRN, suggesting that MRRN may play a more important role for the generation of turning behavior. The sign of the response (i.e., excitation or inhibition) to skin stimulation of a neuron during turns toward (ipsilateral), or away from (contralateral) the side of the cell body was always the same. The cells could thus be divided into four types: 1) cells that were excited during ipsilateral turns and inhibited during contralateral turns; these cells provide an asymmetric excitatory bias to spinal networks and presumably play an important role for the generation of turns; these cells were common (n = 35; 52%) in both MRRN and PRRN; 2) cells that were excited during turns in either direction; these cells were common (n = 19; 28%), in particular in MRRN; they could be involved in a general activation of the locomotor system after skin stimulation; some of the cells were also more activated during turns in one direction and could contribute to an asymmetric turn command; 3) one cell that was inhibited during ipsilateral turns and excited during contralateral turns; and 4) cells (n = 12; 18%) that were inhibited during turns in either direction. In summary, our results show that, in the lamprey, the large majority of reticulospinal cells have responses during lateral turns that are indicative of a causal role for these cells in turn generation. This also suggests a considerable overlap between the command system for lateral turns evoked by skin stimulation, which was studied here, and other reticulospinal command systems, e.g., for lateral turns evoked by other types of stimuli, initiation of locomotion, and turns in the vertical planes.

Activity of reticulospinal neurons during locomotion in the freely behaving lamprey.

The reticulospinal (RS) system is the main descending system transmitting commands from the brain to the spinal cord in the lamprey. It is responsible for initiation of locomotion, steering, and equilibrium control. In the present study, we characterize the commands that are sent by the brain to the spinal cord in intact animals via the reticulospinal pathways during locomotion. We have developed a method for recording the activity of larger RS axons in the spinal cord in freely behaving lampreys by means of chronically implanted macroelectrodes. In this paper, the mass activity in the right and left RS pathways is described and the correlations of this activity with different aspects of locomotion are discussed. In quiescent animals, the RS neurons had a low level of activity. A mild activation of RS neurons occurred in response to different sensory stimuli. Unilateral eye illumination evoked activation of the ipsilateral RS neurons. Unilateral illumination of the tail dermal photoreceptors evoked bilateral activation of RS neurons. Water vibration also evoked bilateral activation of RS neurons. Roll tilt evoked activation of the contralateral RS neurons. With longer or more intense sensory stimulation of any modality and laterality, a sharp, massive bilateral activation of the RS system occurred, and the animal started to swim. This high activity of RS neurons and swimming could last for many seconds after termination of the stimulus. There was a positive correlation between the level of activity of RS system and the intensity of locomotion. An asymmetry in the mass activity on the left and right sides occurred during lateral turns with a 30% prevalence (on average) for the ipsilateral side. Rhythmic modulation of the activity in RS pathways, related to the locomotor cycle, often was observed, with its peak coinciding with the electromyographic (EMG) burst in the ipsilateral rostral myotomes. The pattern of vestibular response of RS neurons observed in the quiescent state, that is, activation with contralateral roll tilt, was preserved during locomotion. In addition, an inhibition of their activity with ipsilateral tilt was clearly seen. In the cases when the activity of individual neurons could be traced during swimming, it was found that rhythmic modulation of their firing rate was superimposed on their tonic firing or on their vestibular responses. In conclusion, different aspects of locomotor activity-initiation and termination, vigor of locomotion, steering and equilibrium control-are well reflected in the mass activity of the larger RS neurons.

Simulations of neuromuscular control in lamprey swimming.

The neuronal generation of vertebrate locomotion has been extensively studied in the lamprey. Models at different levels of abstraction are being used to describe this system, from abstract nonlinear oscillators to interconnected model neurons comprising multiple compartments and a Hodgkin-Huxley representation of the most relevant ion channels. To study the role of sensory feedback by simulation, it eventually also becomes necessary to incorporate the mechanical movements in the models. By using simplifying models of muscle activation, body mechanics, counteracting water forces, and sensory feedback through stretch receptors and vestibular organs, we have been able to close the feedback loop to enable studies of the interaction between the neuronal and the mechanical systems. The neuromechanical simulations reveal that the currently known network is sufficient for generating a whole repertoire of swimming patterns. Swimming at different speeds and with different wavelengths, together with the performance of lateral turns can all be achieved by simply varying the brainstem input. The neuronal mechanisms behind pitch and roll manoeuvres are less clear. We have put forward a 'crossed-oscillators' hypothesis where partly separate dorsal and ventral circuits are postulated. Neuromechanical simulations of this system show that it is also capable of generating realistic pitch turns and rolls, and that vestibular signals can stabilize the posture during swimming.

Gyroscopic Effects of Liquid Ballast on Tractor Stability

Gyroscopic effects of liquid-ballasted tires on the stability of tractors making lateral turns were predicted. This analysis used mathematical formulas to determine the torques produced by the centrifugal and gyroscopic forces. Gyroscopic forces due to the tires, tires with wheel weights, and tires with liquid ballast reduced the speed at which lateral tipping occurs by an average of 1.5, 2.4, and 6.4%, respectively, when compared to previous methods of calculation. The results from 84 tractors investigated show that forces created by the gyroscopic effect are significant, and should be included in the dynamic analysis of tractors making lateral turns.

The effects of head and eye turns on the right ear advantage in dichotic listening

The aim of the present experiment was to investigate the effects of head and eye turns on the ear advantage in dichotic listening (DL) to CV-syllables. Since head and eye turns also mean focusing attention to either the left or right side in space, a second aim was to evaluate recent arguments that ear advantages seen in DL are caused by the perceived position in space of the sound source. Forty right-handed females had 36 trials of CV-syllables under four different instructions. One group ( n = 20) was instructed to turn their head (but not their eyes) to the right, the left, or straight ahead during stimulus presentations. The fourth condition was a standard (no instruction) condition. A second group ( n = 20) had the same instructions but were told to turn their eyes instead of their heads. Conditions were pseudo-counterbalanced across subjects. Consistent with other studies, results showed a right ear advantage (REA) in both groups during all conditions. However, the REA was largest for the standard condition. Also, more subjects showed a REA during the standard condition, and especially compared to the turn-right condition. It is concluded that dichotic performance is not caused by selective attention to either side in space, and that lateral turns of the head and the eyes contralateral to the left hemisphere have an inhibitory (if anything) effect on the REA.

Jet-directed catheter for interventional radiology.

A new catheter of dual lumen construction, suitable for clinical use, is capable of navigating acute vessel branches by selective retrojet fluid thrusts issuing from cowlings built into its distal sidewalls. Conventional radiopaque liquids can be used both to drive the system and to fluoroscopically locate its position relative to the vascular network. In vitro studies have shown the catheter to traverse straight vessels and negotiate difficult lateral turns over short radii in the process of entering progressively smaller branches. In vivo studies have verified these capabilities and suggest a means for embolizing tumors and arteriovenous malformations located at otherwise inaccessible regions. For arterial infusion of drugs to treat tumors, the turbulent jet action is utilized to enhance mixing within the blood stream to overcome the streaming phenomenon common to other catheters. The result is better distribution of the agent and increased opportunity for the drug to reach more of the tumor. The catheter system is undergoing clinical trials.

External Drag of Fuselage Side Intakes

1 Connor, M. A., of a Lateral Turn at Constant Height, AIAA Journal, Vol. 5, No. 7, Feb. 1967, pp. 335-338. 2 Bryson, A. E. and Lele, M. L., Minimum Fuel Lateral Turns at Constant Altitude,'' AIAA Journal, Vol. 7, No. 3, March 1969, pp.559-560. 3 Bryson, A. E. and Hedrick, J. K., Minimum Turns for a Supersonic Aircraft at Constant Altitude, Journal of Vol. 8, No. 3, March 1971, pp. 182-187. 4 Bryson, A. E. and Hedrick, J. K., Three Dimensional, Minimum-Fuel Turns for a Supersonic Aircraft, AIAA Guidance, Control, and Flight Mechanics Conference, Hempstead, N.Y., Aug. 1971. 5 Beebee, W., Time Optimal Co-ordinated Turns Using Methods, Measurement Systems Laboratory Rept, May 1970, MIT, Cambridge, Mass. 6 Kelley, H. J. and Edelbaum, T. N., Energy Climbs, Turns, and Asymptotic Expansions, Journal of Vol. 7, No. 1, Jan.-Feb. 1970, pp. 93-95. 7 Boyd, J. R. and Christie, T. P., Energy Maneuverability Theory and Applications, Paper for 12th Annual Air Force Science and Engineering Symposium, Oct. 1965. 8 Hedrick, J. K., Optimal Three-Dimensional Turning Maneuvers for Supersonic Ph.D. dissertation, 1971, Dept. of Aeronautics and Astronautics, Stanford Univ., Stanford, Calif. 9 Bryson, A. E., Desai, M. N., and Hoffman, W. L., The State Approximation in Performance Optimization of Supersonic Aircraft, Journal of Vol. 6 Nov.-Dec. 1969, pp. 481-487.

Unusual features of the T-system of the pectoralis muscle of the chicken

The T-system of the pectoralis muscle of the chicken was studied by the presentation of a high concentration of horseradish peroxidase to a localized area of skeletal muscle. The entire T-system of each individual muscle fiber was filled with the cytochemical tracer. The demonstrated tubular system lacked uniformity in shape and distribution with many T-tubules making lateral turns, coursing in a longitudinal direction and exhibiting extensive branching. An unusual circular array of tubules was also present. In the immediate subsarcolemmal area a moderately high degree of micropinocytotic activity was observed. The described features are unusual in comparison to muscle fibers of other vertebrates.

Minimum fuel lateral turns at constant altitude.

Thrust, bank angle and angle of attack of aircraft minimum fuel lateral turns at constant altitude and specified velocities