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PubMed1985

Eye and head movements in the pigmented rat.

Vestibular, optokinetic, and spontaneous eye and head movements have been examined in the hooded rat. Eye movement range was 18-20 degrees, and frequency of ocular saccades was 5-20/min; there was a weak linkage of eye and head movements and a weak vestibulocollic reflex. Response to optokinetic stimulation with unity gain (eye velocity matches drum velocity) was seen only at velocities below 1 deg/sec; maximal eye velocity evoked by drum velocities of over 20 deg/sec never exceeded 4-6 deg/sec. These motor responses were not altered by head movements: thus, gaze velocity is not improved by optocollic (head movement) responses, and such optocollic activity occurs only when substantial retinal image motion is present.

Animals↗
PubMed1977

Eye- and head movements in freely moving rabbits.

1. Eye- and head movements were recorded in unrestrained, spontaneously behaving rabbits with a new technique, based upon phase detection of signals induced in implanted coils by a rotating magnetic field. 2. Movements of the eye in space were exclusively saccadic. In the intersaccadic intervals the eyes were stabilized in space, even during vigorous head movements. Most of this stability was maintained in darkness, except for the occurrence of slow drift. 3. Many saccades were initiated while the head was stationary. They were accompanied by a similar, but slower head rotation with approximately the same amplitude. The displacement of the eye in space was a pure step without appreciable under- or over-shoot. The deviation of the eye in the head was mostly transient. 4. Other saccades were started while the head was moving and were possibly fast phases of a vestibulo-ocular reflex. The time course of the eye movement in space was identical for all saccades, whether the head was moving prior to the saccade or not. Eye movements without any head movement were not observed. 5. Saccades were mostly large (average 20-6 +/- 12-4 degrees S.D.) and never smaller than 1 degree. The relations of maximal velocity and duration to amplitude were similar to those reported for man. 6. Visual pursuit of moving objects, when elicited, was only saccadic and never smooth. 7. It is concluded that the co-ordination and dynamics of the rabbit's head- and eye movements are similar to those of primates. In the absence of foveal specilization, the eye movements are restricted to a rather global redirection of the visual field, possibly in particular of the binocular area.

Animals↗
PubMed1995

Head movement trajectory in three-dimensional space during orienting behavior toward visual targets in rhesus monkeys.

Head movement trajectories in three-dimensional space were studied in two monkeys with their heads free during natural and spontaneous orienting behavior toward objects of interest displayed in a horizontal plane. The main interest of this study lies in understanding the process responsible for behavioral variability during the execution of head movements, with special reference to "units of movement." The head movements were recorded by an optoelectronic movement analyzer working with passive markers. Algorithms have been designed to reconstruct the three-dimensional trajectories of the center of gravity of the head. Simultaneously, electromyographic activity in the four pairs of suboccipital muscles was studied. A quantitative evaluation of the involvement of the head in orienting behavior toward visual targets shows that the gaze shift is always produced by eye movements in combination with head movements, even with target eccentricities of less than 10 degrees. On the basis of 80 trials performed by the two monkeys, head trajectories and recruitment patterns of the four pairs of suboccipital muscles have been analyzed. We have been able to identify four elementary kinematic units which can be described as a rightward or leftward turning associated with a contralateral or ipsilateral bending. Each of these four elementary units are underlain by a precise fixed recruitment pattern in the four pairs of suboccipital muscles. These four sets of motor strategies can be combined in order to offer a certain amount of plasticity from which the animal builds its own head trajectory.

Animals↗
PubMed2004

Electrical stimulation of rhesus monkey nucleus reticularis gigantocellularis. I. Characteristics of evoked head movements.

The nucleus reticularis gigantocellularis (NRG) receives monosynaptic input from the superior colliculus (SC) and projects directly to neck motor neuron pools. Neurons in NRG are well situated to play a critical role in transforming SC signals into head movement commands. A previous study of movements evoked by NRG stimulation in the primate reported a variety of ipsilateral and contralateral head movements with horizontal, vertical and torsional components. In addition to head movements, it was reported that NRG stimulation could evoke movements of the pinnae, face, upper torso, and co-contraction of neck muscles. In this report, the role of the rhesus monkey NRG in head movement control was investigated using electrical stimulation of the rostral portion of the NRG. The goal was to characterize head movements evoked by NRG stimulation, describe the effects of altering stimulation parameters, and assess the relative movements of the eyes and head. Results indicate that electrical stimulation in the rostral portion of the NRG of the primate can consistently evoke ipsilateral head rotations in the horizontal plane. Head movement amplitude and peak velocity depend upon stimulation parameters (primarily frequency and duration of stimulation trains). During stimulation-induced head movements the eyes counter-rotate (presumably a result of the vestibulo-ocular reflex: VOR). At 46 stimulation sites from two subjects the average gain of this counter-rotation was -0.38 (+/-0.18). After the end of the stimulation train the head generally continued to move. During this epoch, after electrical stimulation ceased, VOR gain remained at this reduced level. In addition, VOR gain was similarly low when electrical stimulation was carried out during active fixation of a visual target. These data extend existing descriptions of head movements evoked by electrical stimulation of the NRG, and add to the understanding of the role of this structure in producing head movements.

Animals↗
PubMed1987

Vestibular nuclear neuron activity during active and passive head movement in the alert rhesus monkey.

Responses of single neurons were recorded in the medial and descending vestibular nuclei (MVN and DVN) and in the deep cerebellar nuclei of three juvenile rhesus monkeys (Macaca mulatta). Neuronal activity was measured during both passive sinusoidal and nonsinusoidal whole body rotation (peak velocities were under 90 degrees/s) and during active head movements. Although the active head movements occasionally exceeded 300 degrees/s, most exhibited peak velocities of less than 200 degrees/s. A total of 133 units sensitive to horizontal head rotation were recorded, and of these, 38 were held for sufficient time to obtain both passive and active head movement data. Comparison of the neuronal firing patterns obtained during active and passive head movements revealed no apparent differences. Thus neurons that were observed to burst or pause during saccades with the head fixed continued to do so when the head was free. Both the sensitivity to head velocity and the "inferred" spontaneous firing rate were compared during active and passive head movements by plotting rate-velocity curves for both conditions. When the data points were fitted with linear regression lines, no statistically significant differences in either sensitivity or spontaneous rate were found. The present study provides no evidence that efferent vestibular activity alters the properties of afferent vestibular neurons during active head movements, as has previously been suggested (21). Furthermore, neurons in the rostral portions of the vestibular nuclei in primates encode head velocity based entirely on labyrinthine information. Neither neck proprioceptors nor an efference copy of the head movement motor program seem to contribute significantly to the firing patterns observed.

Animals↗
PubMed2003

Vestibular signals of posterior parietal cortex neurons during active and passive head movements in macaque monkeys.

The posterior parietal cortex may function as an interface between sensory and motor cortices and thus could be involved in the formation of motor plans as well as abstract representations of space. We have recorded from neurons in the intraparietal sulcus, namely, the ventral and medial intraparietal areas (VIP and MIP, respectively), and analyzed their head-movement-related signals in relation to passive and active movements. To generate active head movements, we made the animals track a moving fixation spot in the horizontal plane under head-free conditions. When under certain circumstances the animals were tracking the fixation spot almost exclusively via head movements, a clear correlation between neuronal firing rate and head movement could be established. Furthermore, a newly employed paradigm, the "replay method," made available direct comparison of neuronal firing behavior under active and passive movement conditions. In such case, the animals were allowed to make spontaneous head movements in darkness. Subsequently, the heads were fixed and the previously recorded active head-movement profile was reproduced by a turntable as passive stimulation. Neuronal responses ranged from total extinction of the vestibular signal during active movement to presence of activity only during active movement. Furthermore, in approximately one-third of the neurons, a change of vestibular on-direction depending on active versus passive movement mode was observed, that is, type I neurons became type II neurons, etc. We suggest that the role of parietal vestibular neurons has to be sought in sensory space representation rather than reflex behavior and motor control contexts.

Animals↗
PubMed2001

Head movement during sudden base translations as a measure of risks for falls in the elderly.

OBJECTIVE: To determine whether head movement in response to a sudden platform translation differs between healthy young subjects and healthy elderly with and without, bipedal sensory loss. DESIGN: A cross-sectional study with four-way comparison on subject grouping and three test conditions. BACKGROUND: Head movement has been used as a measure of balance in the elderly during voluntary movements. Studies during involuntary movement, however, are limited. Moreover, it is not clear how head movement during involuntary activities relates to postural balance and susceptibility to falls. METHODS: Head movement during a sudden base translation was measured in three subject groups: 9 healthy young, 10 healthy elderly adults and 10 elderly adults with vibratory sensation loss under the feet. The surface compliance of the supporting base, the direction of the base translation and the visual condition were all varied. RESULTS: There were significant differences among the three groups in head range of excursion (5 degrees, 9 degrees, 13 degrees for the young, elderly, and elderly with severe vibratory sensation loss, respectively), onset time (120, 150, 180 ms), and the time from peak to peak (38, 29, 25 ms). A backward base movement increased the head movement more than a forward base movement. CONCLUSIONS: During sudden base translation balance tasks, head movement is significantly increased in the elderly, especially in those elderly adults who are susceptible to falls. The results suggest that an increased head movement in the elderly might be an indication of increased risks for falls.

Accidental Falls↗
PubMed2004

Signal processing in the vestibular system during active versus passive head movements.

In everyday life, vestibular receptors are activated by both self-generated and externally applied head movements. Traditionally, it has been assumed that the vestibular system reliably encodes head-in-space motion throughout our daily activities and that subsequent processing by upstream cerebellar and cortical pathways is required to transform this information into the reference frames required for voluntary behaviors. However, recent studies have radically changed the way we view the vestibular system. In particular, the results of recent single-unit studies in head-unrestrained monkeys have shown that the vestibular system provides the CNS with more than an estimate of head motion. This review first considers how head-in-space velocity is processed at the level of the vestibular afferents and vestibular nuclei during active versus passive head movements. While vestibular information appears to be similarly processed by vestibular afferents during passive and active motion, it is differentially processed at the level of the vestibular nuclei. For example, one class of neurons in vestibular nuclei, which receives direct inputs from semicircular canal afferents, is substantially less responsive to active head movements than to passively applied head rotations. The projection patterns of these neurons strongly suggest that they are involved in generating head-stabilization responses as well as shaping vestibular information for the computation of spatial orientation. In contrast, a second class of neurons in the vestibular nuclei that mediate the vestibuloocular reflex process vestibular information in a manner that depends principally on the subject's current gaze strategy rather than whether the head movement was self-generated or externally applied. The implications of these results are then discussed in relation to the status of vestibular reflexes (i.e., the vestibuloocular, vestibulocollic, and cervicoocular reflexes) and implications for higher-level processing of vestibular information during active head movements.

Afferent Pathways↗
PubMed2006

Computerized dynamic visual acuity with volitional head movement in patients with vestibular dysfunction.

OBJECTIVES: Patients with uncompensated vestibular dysfunction frequently report blurred vision during head movement, a symptom termed oscillopsia. One way to measure the functional deficit associated with an impaired vestibulo-ocular reflex is by comparing visual acuity from a baseline condition in which there is no head movement to visual acuity obtained during a dynamic condition with head movement. A previously described test incorporated a treadmill upon which patients walked during assessment of visual acuity. The objective of the current investigation was to evaluate an alternative method of assessing dynamic visual acuity that uses volitional head movement instead of walking on a treadmill. METHODS: Fifteen participants with normal vestibular function and 16 participants with impaired vestibular function were enrolled. All participants performed the visual acuity task under baseline conditions with no movement and also under dynamic conditions that included 1) walking on a treadmill and 2) volitionally moving their head in the vertical plane. RESULTS: No difference in performance was observed between the treadmill task and the volitional head movement task. Participants with impaired vestibular function performed more poorly under the dynamic conditions than did participants with normal vestibular function. CONCLUSIONS: The results suggest that the volitional head movement paradigm may be useful in identification of patients with functional deficits of the vestibulo-ocular reflex.

Adult↗
PubMed1992

Single-unit activity in the globus pallidus and neostriatum of the rat during performance of a trained head movement.

Single-unit extracellular neuronal recordings were obtained from the globus pallidus (GP) and the neostriatum (NS) of rats while they performed a learned head movement in response to an auditory cue. In both GP and NS, units that altered their discharge rate in association with head movements and with the cues that triggered these head movements were prevalent. Frequently, the responses were directionally-specific (i.e., the magnitude or direction of change in firing rate of these neurons was substantially different for trials in which head movements were made to the left vs. the right). For some units, firing rates were altered only in response to the movement cue or only in association with head movements. However, the majority of neurons exhibited responses with both cue-related and movement-related components. Neuronal responses to the auditory cue usually were context-dependent, in that they did not occur if the same stimulus was presented when the animal was not performing the task. At least a small proportion of GP and NS neurons also appeared to exhibit context-dependent movement-related activity, in that responses occasionally were observed that were associated either with sensory-triggered head movements or with spontaneous head movements, but not with both. These data are consistent with previous suggestions that the activity of basal ganglia neurons during movement performance is highly dependent on the conditions associated with movement initiation. The data also indicate that the response characteristics of both GP and NS neurons in the rat are generally similar to those that have been described for basal ganglia neurons in primates and cats during sensory-triggered movement tasks. However, the proportion of task-related neurons that exhibited responses with both movement-related and cue-related components was greater than has generally been reported in studies of cats and primates, suggesting that neurons with these response properties may be more predominant in the rat basal ganglia.

Acoustic Stimulation↗
PubMed1980

Eye and head movements in reading-disabled and normal children.

Coordination of eye and head movements on nonreading tasks was investigated in 16 reading-disabled and 18 normal children aged 6 to 11 years. Types of eye movements are described and mechanisms controlling eye and head movement are reviewed. Significant differences were found between the two groups in sequencing of eye and head movements that were made in response to the appearance of visual stimuli at unexpected times and positions. Some reading-disabled children also were found to require more eye movements to achieve fixation on targets at known positions. It is suggested that the vestibular system may be implicated as a factor in the results obtained from the reading-disabled children and that the atypical eye-head movement patterns observed may did in stabilizing their visual world.

Adult↗
PubMed2002

The influence of head movement on the accuracy of a rapid pointing task.

BACKGROUND: Eye-hand coordination contributes to sports performance. The positive effect of head movement on the accuracy of eye-hand coordination of some subjects has been demonstrated for self-paced or single tasks, but not for rapid, repetititive tasks, such as those sometimes required in sports. The purpose of this study was to determine whether head movement is detrimental to performance of a rapid, repetitive pointing task. METHODS: Pointing accuracy and speed were tested using the AcuVision 1000 trainer, a device designed to assess and train eye-hand coordination. Twenty-six subjects participated. In one trial, subjects were told to turn their heads toward the targets as they pointed at them. In a second trial, subjects were told to keep their heads stationary as they pointed at the targets. The order of the trials was counter-balanced and subjects were randomly assigned to one of the orders. RESULTS: Pointing accuracy was significantly greater in the head movement trial than in the no head movement trial. CONCLUSIONS: Head movement increased the accuracy of this rapid task. Head movement probably allows more-accurate encoding of target position by maintaining the eyes in less-eccentric positions of gaze.

Adolescent↗
PubMed1994

Human vestibulo-ocular responses to rapid, helmet-driven head movements.

High-frequency head rotations in the 2-20 Hz range and passive, unpredictable head acceleration impulses were produced by a new technique, utilizing a helmet with a torque motor oscillating a mass. Unrestrained head and eye movements were recorded using magnetic sensor coils in a homogeneous magnetic field. In order to analyze the influence of the visual system on the vestibulo-ocular reflex (VOR), we took measurements under three experimental conditions: (1) with a stationary visual target; (2) in total darkness with the subject imagining the stationary target; and (3) with a head-fixed target. The results in 15 healthy subjects were highly consistent. At 2 Hz, VOR gain was near unity; above 2 Hz, VOR gain started to decrease, but this trend reversed beyond 8 Hz, where the gain increased continuously up to 1.1-1.3 at 20 Hz. Phase lag increased with frequency, from a few deg at 2 Hz to about 45 degrees at 20 Hz. Above 2 Hz, VOR gain was not significantly different for the three experimental conditions. Head acceleration impulses produced a VOR with near-unity gain in both directions. We also tested three subjects with clinically total bilateral loss of labyrinthine functions. These labyrinthine-defective subjects showed, in comparison to the normal subjects, strikingly lower gains and much longer delays in the VOR during sinusoidal and step-like head movements. These results suggest that our new torque-driven helmet technique is effective, safe and convenient, enabling the assessment of the VOR at relatively high frequencies where both visual and mental influences are minimized.

Eye Movements↗
PubMed2007

Infant eye and head movements toward the side opposite the cue in the anti-saccade paradigm.

BACKGROUND: The anti-saccade task, when people must respond in the direction opposite to a visual stimulus, has been used as a marker of operation of the frontal cortical oculomotor area. However, early development of oculomotor control has been little studied with the infant anti-saccade paradigm, and a few studies did not recognize anti-saccades in infants in light of the results of adult anti-saccade. Since the characteristics of infant eye movements are little known, applying the criteria used in adult study is by no means the best way to study infant anti-saccade. As it is indicated that coordinated eye and head movements often enable infants to control the direction of their gaze, head movements should be examined as an infant orienting response. The aim of this study was to address how infants used eye and head movements during the anti-saccade paradigm. To distinguish infants' responses, we also investigated eye and head movements during a task for an inhibition of return. Inhibition of return, in which delayed responses occur in the direction to which attention had previously been oriented, has been thought to mark activity of the superior colliculus. Since the superior colliculus is thought to develop much earlier in life than the frontal lobes, we thought it useful to compare these task performances during infancy. METHODS: Infants were divided into three groups according to age. Anti-saccade and inhibition-of-return tasks were given. Their eye and head movements during tasks were independently recorded by the corneal reflection method in the head-free condition. RESULTS: Younger infants tended to initiate eye movement less than older ones in both tasks. In the anti-saccade task, responses opposite to the cue tended to show longer latency than responses to the cue. Infants made faster responses toward the side opposite the cue when it was to the right than when it was left of fixation. Regarding the comparison of responses toward the side opposite the cue between two tasks, the leftward eye movement was faster than the leftward head movements in the inhibition-of-return task, while no difference of latency was observed between eye and head movements in the anti-saccade task. A qualitative analysis of the trajectory of these responses revealed that head movement trajectories were steeper in the anti-saccade than in the inhibition-of-return task. CONCLUSION: Younger infants move head and eyes together, with head movements frequently starting first. On the other hand, both the leftward latency difference between eye and head and gentle trajectories of head in inhibition of return indicate that eye movements are more predominant over head movements in the inhibition-of-return task than in the anti-saccade task. This would suggest an earlier developing inhibition-of-return mechanism.

Journal Article↗
PubMed2006

The role of overt head movement and attention in persuasion.

This study examined the effect of overt head movement on attitudes toward a product. In a headphones test, participants were required to listen to music and to either nod or shake their heads. Some participants listened to a CD of music; other participants listened to a CD of the same music and a persuasive message about the headphones. Overt head movement affected participants' product choice and price perception when they were presented with the music and a persuasive message. The findings are interpreted to suggest that head movement can be instrumental in participants' product evaluation if the head movement is directed or focused on the attitude object.

Adult↗
PubMed1984

Elicitation of motion sickness by head movements in the microgravity phase of parabolic flight maneuvers.

During parabolic flight maneuvers in a Boeing KC-135 aircraft 44 college students were tested for motion sickness susceptibility. These subjects were categorized as 1) insusceptible, 2) moderately susceptible, or 3) highly susceptible to motion sickness during exposure to varying gravitoinertial force levels. After categorization, they were tested in the microgravity phase of parabolic flight to see how three types of head movements affected their baseline susceptibility. The head movements evaluated included side-to-side swivel, shoulder-to-shoulder roll, and front-up head and trunk movements; each type of head movement was used on a separate test day for eyes-open and eyes-covered conditions. Ten cycles of head movements were made in each parabola until a motion sickness endpoint, nausea, was reached or 40 parabolas had been completed. All types of head movements significantly increased susceptibility for subjects in all categories; eyes-open conditions were always more stressful than eyes-closed for each kind of head movement. These findings show unequivocally that natural head movements in microgravity can elicit symptoms of motion sickness. They suggest that head movements play an important etiological role in space motion sickness. In ground based studies where head movements are necessary to elicit symptoms, they are also necessary to elicit adaptation. We describe the use of paced and incremented head movement schedules as a possible way of partially alleviating space motion sickness.

Aerospace Medicine↗
PubMed1984

Involvement of head movement in speech production and its implications for language pathology.

Analysis of head movement during speech, monitored by the polarized light goniometer, showed that head movement accompanies speech almost continuously in a manner specific to the concomitant, suprasegmental speech features. Thus initiation of speech after long pauses was accompanied by wide, linear movements (PS). The termination of speech in a pause (terminal juncture) was accompanied by movements of medium amplitudes and frequencies (OM). Sharp, intense movements (RM) were indicative of a peak in loudness, and often of a major phonetic stress. Finally, a speech disturbance was accompanied by movement if it involved a sharp prosodic transition. We suggest that these correlations indicate that head movement may have a role in speech production, regulating the many degrees of freedom and the dissipation of energy in speech. Furthermore, head movements may play a role in linguistic processing through the generative functions of stress, prominence, and orienting responses. Implications for speech pathology, especially dysphasia, are discussed.

Aphasia↗