Frequency Of Head Movements Research Articles

Distance estimation in the mongolian gerbil: The role of dynamic depth cues

The role of dynamic depth cues in distance estimation was investigated in the Mongolian gerbil. Animals were trained to jump randomly varied distances on a jumping stand under both binocular and monocular conditions. Videotape analysis revealed that prior to jumping, the gerbils executed a series of vertical head movements, the amplitude and velocity of which were related to the gap distance and to each animal's accuracy. This suggested that the gerbils were employing motion parallax cues to judge distance. An inverse relation between the magnitude of forward movement and the frequency of vertical head movements suggested that loom cues were also being used to judge distance. This hypothesis received support from a second experiment in which forward movements were constrained by a short take-off platform. In this condition, frequency of vertical head movements increased, suggesting that a compensation had occurred for the loss of information from loom.

Intraseptally injected opiate agents: Effects on morphine-induced behaviour of cats

Behavioural effects of intraseptally administered opiate agents were analyzed in cats pretreated with an intraperitoneal injection of morphine. In this way, it became possible to investigate (1) the involvement of septal opiate receptors in the behavioural response of cats to systemic administration of morphine, and (2) the pharmacological character of septal opiate receptors. The following results were obtained with intraseptal injections 15–16 min after intraperitoneal morphine: (1) naloxone decreased frequencies of head and limb movements, and (2) morphine was ineffective. The following results were obtained with intraseptal injections 40–41 min after intraperitoneal morphine: (1) β-endorphin and, to a lesser extent, fentanyl increased frequencies of locomotor patterns, (2) morphine and Met-enkephalin were ineffective, (3) naloxone and naltrexone decreased frequencies of locomotor patterns in a dose-dependent way, (4) naloxone and naltrexone antagonized the effects of β-endorphin and fentanyl, and (5) morphine did not attenuate the effect of naloxone. The intraseptal injections affected only the frequencies of the systemically evoked behaviour patterns; the nature of the behaviour patterns remained unchanged. It is concluded that (1) systemically administered morphine does not affect behaviour via a direct action on septal opiate receptors, and (2) the receptors mediating the septally evoked effects are most probably ϵ-type opiate receptors. The hypothesis is put forward that systemic administration of morphine results in an increased release of β-endorphin from hypothalamo-septal neurons and, as a consequence, changes the β-endorphin activity at the ϵ-type opiate receptors in the septum.

Vestibular mechanisms related to vertical and torsional eye movements.

1. A series of experiments concerning the organization of the vertical vestibuloocular reflex (VOR) of the rabbit are reviewed. 2. Unanesthetized, encéphale isolé and intact, alert rabbits have been submitted to natural stimulation of the labyrinth consisting in sinusoidal oscillations and static tilts around the longitudinal axis. The oculomotor responses have been recorded at the level of the III nucleus oculomotor neurons (OMN) and from the four vertical eye muscles. 3. The phase and gain of the OMN response at different frequencies of oscillation indicate a serial involvement of the macular ampullar labyrinthine receptors in the activation of the OMN. In the low frequency range of head movements, macular receptors alone can provide adequate ocular compensation. By raising the frequency of head movements, the threshold value of acceleration for recruiting second order vestibular neurons related to semicircular canals is reached and the vertical VOR is controlled predominantly by the ampullar receptors of the vertical canals. 4. These results have been confirmed and extended in the alert, intact rabbit. By orienting the animal in different positions with respect to the axis of oscillation it has been possible to activate selectively one or the other pair of complementary vertical canals. The EMG responses recorded from the vertical eye muscle exhibited different magnitudes in the different orientations, while the phase curve remained the same. 5. The static otolith-ocular reflex has also been investigated by tilting the alert animals oriented in the same way. The pattern of the EMG responses elicited by the pure macular input coincides with that obtained during dynamic stimulation. The existence of separate functional macular regions specifically connected with the different eye muscles and a close convergent action of the two types of labyrinthine receptors in ocular compensation, are suggested.

Validation of social skills of adolescent males in an interview conversation with a previously unknown adult.

Seventy convicted young male offenders were videotaped during a 5-min standardized interview with a previously unknown adult. In order to determine the social validity of the behavioral components of social interaction for this population, measures of 13 behaviors were obtained from the tapes. These measures were then correlated with ratings of friendliness, social anxiety, social skills performance, and employability made by four independent adult judges from the same tapes. It was found that measures of eye contact and verbal initiations were correlated significantly with all four criterion rating scales. The frequencies of smiling and speech dysfluencies were both significantly correlated with ratings of friendliness and employability. The amount spoken was found to be a significant predictor of social skills performance whereas the frequency of head movements influenced judgments of social anxiety. The latency of response was negatively correlated with social skills and employability ratings and the frequency of question-asking and interruptions correlated significantly with friendliness, social skills, and employability ratings. Finally, the levels of gestures, gross body movements, and attention feedback responses were not found to influence judgments on any of the criterion scales. The implications of the study for selection of targets for social skills training for adolescent male offenders are discussed.

A comparison of the horizontal and vertical optokinetic reflexes of the rabbit.

The horizontal and vertical monocular optokinetic reflexes of the rabbit were measured under closed-loop and open-loop conditions. A random noise, optokinetic stimulus subtending 70×70 deg was presented to the left eye of rabbits placed in front of a rear projection tangent screen. The position of the right eye (nonstimulated) was measured using an infrared light projection technique. During open-loop optokinetic stimulation the eye position signal was fed back to sum with a time-integrated velocity command signal driving the optokinetic stimulus. The dynamics of eye movements evoked by horizontal and vertical optokinetic stimulation were different. Horizontally evoked eye movements never exceeded a deviation of 15 deg before being interrupted by resetting saccades, which returned the eye past the primary position. By contrast, vertical eye deviations greater than 20 deg were often maintained for intervals exceeding 10 s without resetting. The closed-loop gain of optokinetically evoked horizontal eye movements was higher for monocular posterior-anterior optokinetic stimulation than for anterior-posterior stimulation. The vertical optokinetic gain for up-down stimulation was slightly greater than the gain for down-up stimulation. The vertical up-down, open-loop optokinetic gain was greater than the down-up gain over a range of retinal slip velocities of 0.5–5.0 deg/s. Measurement of the horizontal vestibulo-ocular reflex during simultaneous horizontal optokinetic stimulation demonstrated that visual and vestibular information combine linearly to produce reflex eye movements. These data suggest that the higher gain of the horizontal optokinetic reflex may compensate in part for the reduced gain of the horizontal vestibulo-ocular reflex at lower angular accelerations of the head. An equivalent vertical optokinetic gain would be obviated by the contribution of the utricular otoliths to the vertical vestibulo-ocular reflex at low frequencies of head movement.

Compensatory Ocular Movements in Maintaining Gaze

Stabilization of the retinal image during head movements could be performed by reflex oculomotor control by the visual, vestibular and neck proprioceptive systems. It has been known that the visual-oculomotor system primarily acts to maintain gaze when the frequencies of head movements are low (i. e. slow head movements), however, during high frequency head movements the vestibulo- and neck-oculomotor systems have a dominant role. Since the gain of neck-oculomotor reflex is low, the gaze performances during saccades are controlled mostly by way of the vestibulo-ocular reflex (Morasso et al., 1973). Bilateral labyrinthectomy in rheusus monkeys caused a gaze over-shoot up to 4-6 weeks after the operation (Dichgans et al., 1973). Author and others have reported that squirrel monkeys show an over-shoot of gaze during optokinetic stimulation at 3-4 weeks after bilateral lateral semicircular canal block. The over-shoot of gaze was subsided with similar time course in both of these experiments. Compensatory mechanisms underlying the recovery of the gaze, which occurred in CNS after the interference of vestibulo-ocular reflex, were discussed.

Avian Prehatching Behavior: Functional Aspects of the Tucking Pattern

The domestic chick's position at the time of pipping (initial cracking of the eggshell) is important to its hatching success. Normally the anterior end of the chick is at the large end of the egg; the legs, feet, and left wing are flexed; the neck is depressed ventrally; the head is turned to the right, its left side resting on the right pectoral muscle, and is tucked under the partially extended right wing (Fig. la). Six malpositions generally reducing hatchability have been recognized by poultry scientists. Malposition VI, head over the right wing (Fig. lb), reduces hatching, but so slightly that Waters (1935), Byerly and Olsen (1937), Munday (1953) and others did not consider this position abnormal. Hamburger and Oppenheim (1967) detailed the specific prehatching pattern of tucking, the placing of the head under the right wing 1-2 days before pipping. This attitude is maintained throughout the hatching stage of cutting the cap from the shell. It is a genetically consistent behavior pattern of the chick and probably of most birds (see Oppenhelm 1972). Thus I was interested to learn that its absence (producing malposition VI) does not seriously hamper pipping or hatching. This could be explained by the fact that only a very slight selective advantage is necessary to fix an adaptation in a species over a large number of generations, but it still remains to elucidate the function(s) of the wing and the actual selective advantage produced by tucking. What is the function of the normal wing-overhead position? Kuo's (1932) supposition that it is important for the wing to protect the face from the air chamber membrane has been shown invalid by Waters (1935) and Hamburger and Oppenheim (1967). Protection of the head or eyes from sharp shell fragments during the head thrusts of climax could be a function, but the eyes generally remain closed until hatching is completed in precocial birds (Hamburger and Oppenheim 1967), longer in altricial birds, and the eyes may need no extra protection. Also, Oppenheim (1972) stated that the wing in altricial birds does not cover much of the relatively large head. Normal pipping convulsions (Brooks and Garrett 1970) might deform the delicate wing bones if the wing were between thorax and beak in malposition VI. Wing protection is not needed in the hatching climax, however: the thorax does not push against the beak, now, because there is sufficient space in which to elevate the head; and the force does not have to be as great to break the eggshell (which is already broken) further. Yet the wing covers the head throughout. Narayanan and Oppenheim (1968) hypothesized that tucking inhibits head movements. In their experiments involving extirpation of the right wing bud, a significant increase in frequency of head movements was demonstrated, but the cause of the increase was obscured by possible neural modifications due to limb extirpation. Later Oppenheim (1970) re-tested this by manually un-tucking chicks and ducklings, but no significant increase in frequency of head movements was shown this time. In any case, it seems doubtful that a decrease in frequency (rather than amplitude) of head movements would produce the selective pressure necessary to evolve the tucking pattern. In fact, the opposite might be more beneficial.

On the predominance of anti-compensatory eye movements in vestibular nystagmus.

The predominance of anti-compensatory eye movements in vestibular nystagmus recorded during sinusoidal and post-rotational tests is interpreted in terms of a mathematical model of the vestibulo-ocular system. Namely, a direct pathway between the vestibular nuclei and the saccadic mechanism is assumed. In the range of frequencies of natural head movements this pathway carries on a signal proportional to head angular velocity. Therefore, during active head movements the saccadic mechanism is forced to produce quick eye rotations in the direction of head movement and, thus, to cooperate in the task of picking up visual targets outside the visual field. During passive head movements giving rise to nystagmus the assumed pathway contributes to reduce the error in eye resetting due to the saccadic delay. Analytical considerations and simulation results seem to prove the adequacy of the proposed model.