Bird head stabilization

To investigate the characteristics of the head movements and the mechanisms of gaze, stabilization during walking and running, eye and head movements were recorded in 10 normal subjects and 8 patients with labyrinthine lesions, who repeated stepping (1.OHz) and running (1.5Hz) on the same spot. 1. In normal subjects, head displacements during stepping were limited in the vertical, right-left and anteroposterior directions (0.8, 1.5 and 1.5cm on average, respectively), and the head rotations and the eye movements were also small. During running, the increase in the vertical head displacement (5.5cm on average) induced rhythmical pitching motions of the head and vertical eye movements. 2. In patients with labyrinthine lesions, both the horizontal head displacement and the rotation amplitude became twice as large as those in normal subjects during either locomotion, however, horizontal eye movements did not correspondingly increase. The vertical head displacements during running resembled those of normal subjects, but the amplitude of pitching motion of the head significantly decreased. 3) The spatial stabilization of the head during stepping in normal subjects indicated that walking is a suitable locomotion for gaze stabilization. On the other hand, the head was more unstable during running, however, the pitching motions of the head resulting from vertical head displacements seemed to reduce the concussion of the head and produce vertical compensatory eye movements which maintained the gaze stabilization. 4) In patients with labyrinthine lesions, the horizontal eye movements did not compensate the horizontal head movements during walking and running. Furthermore, since the pitching motions of the head could not be produced rhythmically during running, the vertical body oscillations were directly conducted to the head. The abnormalities of the head movements in addition to the insufficient compensations may cause oscillopsia in these patients. 5) The present study indicated that the head stabilization is essential to maintain the gaze stabilization during walking and running and that the semicircular canals-ocular reflexes act a major role in these mechanisms.

The role of compensatory eye and head movements for gaze stabilization in the unrestrained frog

To assess development of reaching and head stability in infants at very high risk (VHR-infants) of cerebral palsy (CP) who did and did not develop CP. This explorative longitudinal study assessed the kinematics of reaching and head sway in sitting in 37 VHR-infants (18 CP) one to four times between 4.7 months and 22.6 months corrected age. Developmental trajectories were calculated using linear mixed effect models. Motor function was evaluated with the Infant Motor Profile (IMP) around 13 months corrected age. Throughout infancy, VHR-infants with CP had a worse reaching quality than infants without CP, reflected for example by more movement units (factor 1.52, 95% CI 1.16-1.99) and smaller transport movement units (factor 1.86, 95% CI 1.20-2.90). Total head sway of infants with and without CP was similar, but infants with CP used more head movement units to achieve stability. The rate of developmental change in infants with and without CP was similar. Around 13 months, head control and reaching quality were interrelated; both were associated with IMP-scores. Infants with CP showed a worse kinematic reaching quality and head stability throughout infancy from early age onwards than VHR-infants without CP, implying that kinematically they do not grow into a deficit, but exhibit deficits from early infancy on. Reaching quality improves throughout infancy in all infants at high risk (VHR-infants). Infants with cerebral palsy (CP) show a worse reaching quality than VHR-infants without CP. Infants with CP achieve head stability differently from infants without CP. Infants with CP exhibit kinematic reaching problems from early age onwards.

Life Is an N of 1

Dynamic posturography by measurement of center of pressure (COP) is a widely employed technique for evaluating the vestibular system. However, the relationship of COP motion to vestibulo-ocular reflex (VOR) function and image stability on the retina has not been determined previously. To assess these relationships, we report gaze, head, and trunk stability during dynamic posturography in 11 normal volunteers, 7 subjects with unilateral vestibular lesions, and 3 subjects with bilateral vestibular lesions. Posturographic tasks consisted of standing still and standing on a platform that was sliding (0.2 Hz), tilting (0.1 Hz), or covered with a foam cushion 6 cm thick while tilting (0.1 Hz). Each perturbation was imposed in the anterior-posterior and repeated in the medial-lateral direction, in both light and darkness. Subjects viewed (or in darkness remembered) a target located 50, 100, or 500 cm distant. COP, angular eye position, and angular and linear orbit and trunk positions were measured using magnetic search coils and flux gate magnetometer sensors. With the target visible, the velocity of image motion on the retina was on average always less than 1 degree/s, well within the range consistent with high visual acuity. In darkness, gaze velocity increased for normal and vestibulopathic subjects. During tilt, vestibulopathic subjects had a significantly greater gaze velocity than controls. Gain of the angular VOR (eye velocity/head velocity) was significantly lower in darkness than in light and in vestibulopathic as compared to control subjects. Gain of the VOR was significantly correlated with gaze instability, but variation in VOR gain accounted for only 20-40% of the variance. In darkness, the velocity of the COP was significantly greater in vestibulopathic than control subjects for every condition tested. In light, this difference was small and often not significant. Although spectral analysis of the COP indicated frequencies above 1 Hz that were not observed in motion of the trunk and orbit, root mean square (RMS) velocities of the trunk and orbit in the horizontal plane were higher in darkness and in vestibulopathic subjects, mirroring COP findings. Only in vestibulopathic subjects tested in darkness was there a correlation between COP velocity and gaze velocity; COP velocity was otherwise uncorrelated with gaze. Gaze velocity was greater with near than with distant targets. Vertical VOR gain was higher with near targets. No other significant effects of target distance were found. Head movement strategy, VOR gain, and COP were all unaffected by target proximity. These data show that gaze velocity measurements during dynamic posturography in darkness are sensitive to vestibular loss. With a visible target, both COP and gaze stability of vestibulopathic subjects are difficult to distinguish from normal. During visual feedback, it is likely that image stabilization over the range of frequencies tested is achieved through better head stability and through visual tracking, allowing vestibulopathic subjects to maintain adequate visual acuity.

Sara Courtneidge: swimming with Srcs

American birds: Audubon was not the first

The relationships between eye and head movements during the viewing of various visual stimuli using a head mounted display (HMD) and a large flat display were compared. The visual sizes of the images displayed were adjusted virtually, using an image processing technique. The negative correlations between head and eye movements in a horizontal direction were significant for some visual stimuli using an HMD and after some practice viewing images. Also, scores of two factors for subjective assessment of viewing stimuli positively correlated with horizontal head movements when certain visual stimuli were used. The result suggests that under certain conditions the viewing of tasks promotes head movements and stimulates correlational relationships between eye and head movements.

Relationship between eye acceleration and retinal image velocity during foveal smooth pursuit in man and monkey.

IntroductionWhile most head movements in daily life are active, most tools used to assess vestibular deficits rely on passive head movements. A single gain value is not sufficient to quantify gaze stabilization efficiency during active movements in vestibular deficit patients. Moreover, during active gaze shifts, anticipatory mechanisms come into play. Our aim was to explore the extent to which previously described compensatory mechanisms are employed in patients with bilateral vestibular loss.MethodsWe used a Video Head Impulse Test (vHIT) to simultaneously record eye and head movements during a video Active Gaze Shift Test (vAGST). Thirty-eight patients with bilateral vestibular deficits and 61 control subjects were tested.ResultsDespite impaired performance on caloric tests and vHIT, most patients exhibited normal gaze stabilization (gain = 0.92 ± 0.1) during active gaze shifts up to a head speed (‘stall speed’) of approximately 140 ± 60°/sec, compared to 280 ± 65°/sec in controls. Our results indicate that BVD patients spontaneously adopt a head speed during active horizontal movements that significantly improves gaze stabilization compared to passive movements. The stall speed correlates with the spontaneous head speed typically adopted by BVD patients and controls in daily activities. As a consequence of the reduction in head speed and corrective saccades, patients also showed an increased delay in gaze stabilization (413 ± 105 ms in BVD patients versus 358 ± 82 ms in controls) at the end of the gaze shift, which might become disabling for certain tasks.DiscussionRecent model suggests that compensatory eye movements, which stabilize gaze during the counter rotation phase of active gaze shifts, are predictive in nature. vAGST is not designed to provide an etiological diagnosis but rather a functional assessment of the patient’s ability to generate predictive eye movements that compensate for vestibular sensor deficits. Understanding the quality of the patient’s sensory predictions can also shed light on vestibular symptoms, even in cases where no vestibular sensor deficit is detected. This suggest that quality of life and oscillopsia questionnaires should distinguish between predictable and unpredictable movements.

Analytical Derivation of Thermodynamic Properties of Bolalipid Membrabe

Phosphoinositide Binding Domains: Embracing 3-Phosphate

Rags before the riches: Friedrich Miescher and the discovery of DNA.

Owing to several reasons (e.g. changing light conditions) the measurement of eye movement behaviour is often unstable and data loss can occur. It is investigated whether head movement recording could be an alternative to eye movement analysis for measuring distraction through visual secondary tasks in driving. During a 1-h drive in the driving simulator, 16 participants conducted a self-paced menu system task that was designed according to design principles for commercial in-vehicle information systems. Influence of visual distraction was analysed and compared for parameters of eye and head movement. Parameters like percent road centre for head and eye movement and proportion of head movement were calculated. The results show that head movement analysis can differentiate nearly as well between distracted and attentive driving as parameters based on eye movement recording in this task context. It is concluded that head movement analysis seems to be a promising alternative for assessing drivers’ distraction under certain circumstances.

This study explored the dynamics of steady-state visual evoked potentials (SSVEPs) amid unrestricted head and eye movements using immersive virtual reality (VR) to concurrently record eye and head movement data with a 64-channel electroencephalogram (EEG) during a visual fixation task. Employing a dual-condition approach-eye-shifting and head-turning-the trials were time-locked to stimulus onset, Gaze Intersection Point (GIP) onset, and fixation onset. Eye and head velocity, Canonical Correlation Analysis (CCA) correlation, and Inter-Trial Coherence (ITC) were computed across the trial duration. SSVEP signal detection (reflected in CCA scores) was most closely aligned with the GIP onset. The CCA score increase before fixation suggests that visual processing is not fully suppressed during simultaneous head and eye movements. These findings support the potential of SSVEP for tracking the time course of visual processing in naturalistic settings where research participants are free to move their heads and eyes as they explore their three-dimensional environment.