Three-dimensional Head Movements Research Articles

Motor Control: Three-Dimensional Metric of Head Movements in the Mouse Brain

Many forms of human and animal behavior involve head movements. A new study reveals the neural code for three-dimensional head movements in the midbrain of freely moving mice.

Bootstrap prediction bands for cervical spine intervertebral kinematics during in vivo three-dimensional head movements

There is substantial inter-subject variability in intervertebral range of motion (ROM) in the cervical spine. This makes it difficult to define “normal” ROM, and to assess the effects of age, injury, and surgical procedures on spine kinematics. The objective of this study was to define normal intervertebral kinematics in the cervical spine during dynamic functional loading. Twenty-nine participants performed dynamic flexion\\extension, axial rotation, and lateral bending while biplane radiographs were collected at 30 images/s. Vertebral motion was tracked with sub-millimeter accuracy using a validated volumetric model-based tracking process that matched subject-specific CT-based bone models to the radiographs. Gaussian point-by-point and bootstrap techniques were used to determine 90% prediction bands for the intervertebral kinematic curves at 1% intervals of each movement cycle. Cross validation was performed to estimate the true achieved coverage for each method. For a targeted coverage of 90%, the estimated true coverage using bootstrap prediction bands averaged 86±5%, while the estimated true coverage using Gaussian point-by-point intervals averaged 56±10% over all movements and all motion segments. Bootstrap prediction bands are recommended as the standard for evaluating full ROM cervical spine kinematic curves. The data presented here can be used to identify abnormal motion in patients presenting with neck pain, to drive computational models, and to assess the biofidelity of in vitro loading paradigms.

The cervical spine of the American barn owl (Tyto furcata pratincola): I. Anatomy of the vertebrae and regionalization in their S-shaped arrangement.

BackgroundOwls possess an extraordinary neck and head mobility. To understand this mobility it is necessary to have an anatomical description of cervical vertebrae with an emphasis on those criteria that are relevant for head positioning. No functional description specific to owls is available.Methodology/Principal findingsX-ray films and micro-CT scans were recorded from American barn owls (Tyto furcata pratincola) and used to obtain three-dimensional head movements and three-dimensional models of the 14 cervical vertebrae (C1−C14). The diameter of the vertebral canal, the zygapophyseal protrusion, the distance between joint centers, and the pitching angle were quantified. Whereas the first two variables are purely osteological characteristics of single vertebrae, the latter two take into account interactions between vertebrae. These variables change in characteristic ways from cranial to caudal. The vertebral canal is wide in the cranial and caudal neck regions, but narrow in the middle, where both the zygapophyseal protrusion and the distance between joint centers are large. Pitching angles are more negative in the cranial and caudal neck regions than in the middle region. Cluster analysis suggested a complex regionalization. Whereas the borders (C1 and C13/C14) formed stable clusters, the other cervical vertebrae were sorted into 4 or 5 additional clusters. The borders of the clusters were influenced by the variables analyzed.Conclusions/SignificanceA statistical analysis was used to evaluate the regionalization of the cervical spine in the barn owl. While earlier measurements have shown that there appear to be three regions of flexibility of the neck, our indicators suggest 3–7 regions. These many regions allow a high degree of flexibility, potentially facilitating the large head turns that barn owls are able to make. The cervical vertebral series of other species should also be investigated using statistical criteria to further characterize morphology and the potential movements associated with it.

Nystagmus induced by circular head shaking in normal human subjects.

We recorded three-dimensional eye and head movements during circular, horizontal, vertical, and torsional head shaking in six human subjects with normal vestibular function. With circular head shaking, the stimulation of the canals by the termination of the head movement is similar to that following a step in velocity about the naso-occipital axis. A large torsional nystagmus with slow phase eye velocity of about 20 degrees/s was observed upon cessation of circular head shaking. The three-dimensional eye movements expected from stimulation of the semicircular canals by the head-shaking maneuvers were calculated. The predicted activation of the canals was determined by projecting the head velocity (in head coordinates) into the canal planes and then processing the signal with the transfer function of the canals. The torsional eye velocity components predicted by the stimulation of the canals matched the recorded ones. We observed small horizontal eye velocities that could not be predicted by the stimulation of the canals alone. No eye movements were observed after the end of head shaking about a fixed horizontal or vertical axis. The eye velocities following the termination of head oscillations in the roll plane were small. The analysis methods developed for this study may be useful in the investigation of eye movements elicited by other types of three-dimensional head movements.

Rostral Fastigial Nucleus Activity in the Alert Monkey During Three-Dimensional Passive Head Movements

The fastigial nucleus (FN) receives vestibular information predominantly from Purkinje cells of the vermis. FN in the monkey can be divided in a rostral part, related to spinal mechanisms, and a caudal part with oculomotor functions. To understand the role of FN during movements in space, single-unit activity in alert monkeys was recorded during passive three-dimensional head movements from rostral FN. Seated monkeys were rotated sinusoidally around a horizontal earth-fixed axis (vertical stimulation) at different orientations 15 degrees apart (including roll, pitch, vertical canal plane and intermediate planes). In addition, sinusoidal rotations around an earth-vertical axis (yaw stimulus) included different roll and pitch positions (+/-10 degrees, +/-20 degrees). The latter positions were also used for static stimulation. One hundred fifty-eight neurons in two monkeys were modulated during the sinusoidal vertical search stimulation. The vast majority showed a uniform response pattern: a maximum at a specific head orientation (response vector orientation) and a null response 90 degrees apart. Detailed analysis was obtained from 111 neurons. On the basis of their phase relation during dynamic stimulation and their response to static tilt, these neurons were classified as vertical semicircular canal related (n = 79, 71.2%) or otolith related (n = 25; 22.5%). Only seven neurons did not follow the usual response pattern and were classified as complex neurons. For the vertical canal-related neurons (n = 79) all eight major response vector orientations (ipsilateral or contralateral anterior canal, posterior canal, roll, and nose-down and nose-up pitch) were found in Fn on one side. Neurons with ipsilateral orientations were more numerous and on average more sensitive than those with contralateral orientations. Twenty-eight percent of the vertical canal-related neurons also responded to horizontal canal stimulation. None of the vertical canal-related neurons responded to static tilt. Otolith-related neurons (n = 25) had a phase relation close to head position and were considerably less numerous than canal-related neurons. Except for pitch, all other response vector orientations were found. Seventy percent of these neurons responding during dynamic stimulation also responded during static tilt. The sensitivity during dynamic stimulation was always higher than during static stimulation. Sixty-one percent of the otolith-related neurons responded also to horizontal canal stimulation. These results show that in FN, robust vestibular signals are abundant. Canal-related responses are much more common than otolith-related responses. Although for many canal neurons the responses can be related to single canal planes, convergence between vertical canals but also with horizontal canals is common.

Modeling vestibulo-ocular reflexes in everyday activities

Fundamental data for the establishment of a new clinical testing procedure for patients suffering from equilibrium disorders were developed. A mathematical model that predicts vestibulo-ocular reflex responses (eye velocities) to three-dimensional head movements was investigated. An experimental set-up permitting the simultaneous recording of the head and eye movements was developed to investigate the vestibulo-ocular reflex (VOR) during everyday activities. The test results show that computer simulation of the VOR occurring during complex movements is indeed possible. The model was able to predict the trend of the experimentally determined eye velocities. It was ascertained that for the further development of the model, the influence of the cervico-ocular reflex (COR) on the resulting eye velocities also has to be taken into account. The proposed method for investigating patients with equilibrium disorders appears suitable enough to make further development to the clinical stage worthwhile. An adaptation of the feedback amplification parameters of the model to take account of the nature of the stimulus and the influence of COR is needed to improve the agreement between the amplitudes of measured and predicted eye velocities. To reliably quantify the feedback amplification parameters, tests need to be carried out in a large number of subjects.

重度脳性麻痺者を対象とした頭部操作式電動車いすの開発

People having severe cerebral palsy cannot move by themselves due to physical limitation of their limbs. This always constitutes a great handicap for them. The purpose of our work is to facilitate independent movement for such people. We developed an electric powered wheelchair for a severely disabled cerebral-palsied girl. Although she cannot control her limbs, she can move her head as she intends. Measurement of her three-dimensional head movements indicated that she can rotate and flex her neck very well. As a result, her rotation angle and flexion angle were adopted as the controlling parameters. This system consisted of a three-dimensional position and angle sensor (ISOTRAK system), head operating start switches, an emergency stop switch, sensors to prevent collision, and a handheld personal computer. The rotation angle and flexion angle are measured by the ISOTRAK system and processed by computer. The wheelchair turns to the right after a head rotation to the right, and similarly for the left. A nodding movement from the operator stop the wheelchair. Operating functions can be changed by altering the computer software, so it can be easily adapted for other disabled people. The new wheelchair also features a special seating system to reinforce both the ability to control head movements and the postural stability. The subject first drove the wheelchair in a gymnasium which was wide and had a flat surface. She was able to go straight, turn right/left and stop very well. She could also propel herself a previously selected small spot. Next she drove on a pathway in an institution. By delicately controlling the direction, she could turn right/left. And an examination of her driving speed showed that an adequate speed was 2.0km/h. Moreover, we discovered that the tilt angle, which is the angle at which the chair is inclined, affected her head movement. As a result of measuring the change of position during driving, the appropriate angle found to be 22°. In the next phase, she drove on a road and sidewalk on the grounds of our rehabilitation center. She could control the direction by degrees, so that she was able to overcome the narrow width of the sidewalk and the tendency to turn downhill on a side slope. Measurement of her head movement while driving over a curb showed a shock to the neck, but it had no serious effect on control of the wheelchair. In developing a device that facilitates independence the severely disabled people, it is important to grasp the features of the individual, to make it easy to change the control functions, and to evaluate the device's actual action. The possibility of independent movement is greatly increased if all these factors are considered.