In animal navigation, head direction is encoded by head direction cells within the olfactory-hippocampal structures of the brain. Even in darkness or unfamiliar environments, animals can estimate their head direction by integrating self-motion cues, though this process accumulates errors over time and undermines navigational accuracy. Traditional strategies rely on visual input to correct head direction, but visual scenes combined with self-motion information offer only partially accurate estimates. This study proposed an innovative calibration mechanism that dynamically adjusts the association between visual scenes and head direction based on the historical firing rates of head direction cells, without relying on specific landmarks. It also introduced a method to fine-tune error correction by modulating the strength of self-motion input to control the movement speed of the head direction cell activity bump. Experimental results showed that this approach effectively reduced the accumulation of self-motion-related errors and significantly enhanced the accuracy and robustness of the navigation system. These findings offer a new perspective for biologically inspired robotic navigation systems and underscore the potential of neural mechanisms in enabling efficient and reliable autonomous navigation.
Animals ; Neural Networks, Computer ; Calibration ; Spatial Navigation/physiology* ; Head Movements/physiology* ; Neurons/physiology* ; Models, Neurological ; Head/physiology* ; Action Potentials/physiology*

Objective:Exploring the performance characteristics of spontaneous nystagmus（SN） in video-head impulse test（vHIT） and its possible effects on saccade. Methods:Vestibular function tests such as vHIT and SN were conducted in 48 patients with acute unilateral vestibulopathy（AUVP）. The saccade characteristics of vHIT in patients without SN and those with SN were analyzed, as well as the expression characteristics of SN in vHIT. Results:Among the 48 AUVP patients, there were 34 cases with SN, including 31 cases with saccade on the healthy side, 11 cases with both the same and opposite directions of eye movement, 19 with the opposite only, 1 with same direction only, and 3 cases without saccade. There were 14 patients without SN, of whom 10 showed saccade on the healthy side, including 4 with both eye movements in the same and opposite direction, 2 in the opposite direction only, 4 in the same direction only, and 4 without saccade. There is a correlation between reverse saccade on the healthy side and the presence of SN in patients. SN in vHIT can appear opposite to the direction of eye movement on the healthy side, while on the affected side it can appear the same as the direction of eye movement and may cause more discrete overt saccade. 32 patients in the acute phase（≤2 w）, 29 patients with SN, SN intensity of（6.7 ± 3.2） °/s, and 3 patients without SN. 16 cases in non acute phase（>2 w）, 5 cases with SN, SN intensity of（3.7 ± 2.1） °/s, and 11 cases without SN. In the acute phase there were 30 cases of saccade on the healthy side, 10 cases with both the same and opposite direction of eye movement, 18 cases with only the opposite direction, 2 cases with only the same direction and 2 cases without saccade. There is a correlation between the duration of the disease and the occurrence of reverse saccade on the healthy side. The intensity cut off point of SN for reverse saccade is 2.1 °/s in the healthy lateral semicircular canal vHIT. Conclusion:Compensatory saccades and SN waves with similar waveforms are mostly present in vHIT in AUVP patients. SN wave is in the opposite direction of the normal side and eye movement wave, and the affected side and dominant saccade direction are in the same direction and mixed together, which can affect the dispersion and amplitude of overt saccade in vHIT. Accurate identification of SN in vHIT of AUVP patients is not only the key factor to identify compensatory saccade, but also can provide help for the diagnosis and compensatory assessment of AUVP.
Humans ; Head Impulse Test/methods* ; Nystagmus, Pathologic/physiopathology* ; Saccades/physiology* ; Male ; Female ; Vestibular Diseases/physiopathology* ; Middle Aged ; Adult ; Eye Movements/physiology* ; Aged

OBJECTIVE: Smart glasses can provide sonographers with real-time ultrasound images. In the present study, we aimed to evaluate the utility of smart-glasses for ultrasound-guided peripheral venous access.METHODS: In this randomized, crossover-design, simulation study, 12 participants were recruited from the emergency department residents at a university hospital. Each participant attempted ultrasound-guided peripheral venous access on a pediatric phantom at intervals of 5 days with (glasses group) or without (non-glasses group) the use of smart glasses. In the glasses group, participants confirmed the ultrasound image through the lens of the smart glasses. In the non-glasses group, participants confirmed the ultrasound image through the display viewer located next to the phantom. Procedure time was regarded as the primary outcome, while secondary outcomes included the number of head movements for the participant, number of skin punctures, number of needle redirections, and subjective difficulty.RESULTS: No significant differences in procedural time were observed between the groups (non-glasses group: median time, 15.5 seconds; interquartile range [IQR], 10.3 to 27.3 seconds; glasses group: median time, 19.0 seconds; IQR, 14.3 to 39.3 seconds; P=0.58). The number of head movements was lower in the glasses group than in the non-glasses group (glasses group: median, 0; IQR, 0 to 0; non-glasses group: median, 4; IQR, 3 to 5; P<0.01). No significant differences in the number of skin punctures or needle restrictions were observed between the groups.CONCLUSION: Our results indicate that smart-glasses may aid in ensuring ultrasound-guided peripheral venous access by reducing head movements.
Emergency Service, Hospital ; Eyeglasses ; Glass ; Head Movements ; Needles ; Pilot Projects ; Punctures ; Skin ; Ultrasonography ; Wireless Technology

OBJECTIVES: Direction-changing positional nystagmus (PN) was considered to indicate the presence of benign paroxysmal positional vertigo involving lateral semicircular canal in most cases. We investigated the incidence of PN on the supine head-roll test and compared the characteristics of nystagmus in patients with vestibular neuritis (VN) and Meniere disease (MD). METHODS: A retrospective review of patients, who were diagnosed with unilateral VN or unilateral definite MD between September 2005 and November 2011, was conducted. Sixty-five VN patients and 65 MD patients were enrolled. Eye movements were recorded for 30–60 seconds at the positions of sitting, head roll to the right, and head roll to the left, and maximum slow-phase eye velocity was calculated. PN was classified as direction-fixed (paretic or recovery) and direction-changing (geotropic or apogeotropic). RESULTS: Spontaneous nystagmus was observed in 57 patients (87%, the slow-phase eye velocity of 7°/sec±5°/sec) with acute VN, 39 (60%, 2°/sec±1°/sec) with follow-up VN, and 32 (49%, 2°/sec±2°/sec) with MD. Direction-fixed PN was the most common type. Direction-fixed paretic type was most common in acute VN (80%) and follow-up VN (42%), and direction-fixed recovery type was most common in MD (31%). Paretic type was significantly more common in acute VN (80%) than in follow-up VN (42%) and MD (26%), and the recovery type was significantly more common in MD (31%) than in acute VN (3%) and follow-up VN (14%). Direction-changing PN was more common in MD (22%), followed by follow-up VN (14%) and acute VN (9%). CONCLUSION: Though direction-fixed paretic PN was most common in VN and MD patients, direction-changing PN could be observed in a few patients (9%–20%) with peripheral vestibular disorders regardless of the duration from the onset of dizziness, suggesting the presence of otolith-related dizziness.
Benign Paroxysmal Positional Vertigo ; Dizziness ; Eye Movements ; Follow-Up Studies ; Head ; Humans ; Incidence ; Meniere Disease ; Nystagmus, Physiologic ; Retrospective Studies ; Semicircular Canals ; Vestibular Neuronitis

A 22-year-old man was admitted with gradually aggravating stereotypic head movement with hypomania. Brain magnetic resonance imaging showed a large suprasellar arachnoid cyst extending into the third ventricle, with obstructive hydrocephalus, characteristic of bobble-head doll syndrome. Endoscopic fenestration of the suprasellar arachnoid cyst was performed. Stereotypic head movement stopped immediately after surgery and hypomanic symptoms gradually improved within a month. During 4 years of follow-up observation without medication, neuropsychiatric symptoms did not relapse. We report our experience of surgically treating stereotypy and hypomania in a case of bobble-head doll syndrome and discuss the possible neuropsychiatric mechanisms of this rare disease.
Arachnoid ; Arachnoid Cysts ; Bipolar Disorder ; Brain ; Follow-Up Studies ; Head Movements ; Humans ; Hydrocephalus ; Magnetic Resonance Imaging ; Rare Diseases ; Recurrence ; Third Ventricle ; Young Adult

BACKGROUND AND PURPOSE: Although traditionally regarded as spared, a range of oculomotor dysfunction has been recognized in amyotrophic lateral sclerosis (ALS) patients. ALS is nowadays considered as a neurodegenerative disorder of a third compartment comprising widespread areas of extra-motor brain including cerebellum. Our objective was to perform an observational study to examine for ocular motor dysfunction in patients with ALS and for any differences between bulbar-onset and spinal-onset patients. METHODS: Thirty two ALS patients (bulbar onset: 10, spinal onset: 22) underwent the standardized systemic evaluations using video-oculography. RESULTS: Oculomotor dysfunctions such as square wave jerks, saccadic dysmetria, abnormal cogwheeling smooth pursuits and head shaking and positional nystagmus of central origin have been observed in the ALS patients at a relatively early stage. Abnormal smooth pursuits and saccadic dysmetria were increased in the bulbar-onset compared to the spinal-onset (p < 0.05). CONCLUSIONS: These oculomotor abnormalities may be a marker of neuro-degeneration beyond motor neurons in ALS, especially in bulbar-onset disease. Future longitudinal studies of eye movement abnormalities have provided insights into the distribution and nature of the disease process.
Amyotrophic Lateral Sclerosis* ; Brain ; Cerebellar Ataxia ; Cerebellum ; Eye Movements ; Head ; Humans ; Longitudinal Studies ; Motor Neurons ; Neurodegenerative Diseases ; Nystagmus, Physiologic ; Observational Study ; Pursuit, Smooth

OBJECTIVE: A radial arm maze (RAM) is an essential tool for assessing spatial learning and memory. Although this tool is widely used to study deficits in spatial memory in animal models, it has several restrictions that prevent its adaptation to human research and training. Therefore, we developed a head-mounted-display RAM (HMD-RAM) program for humans and verified its validity by comparing it to the results obtained by previous RAM studies. We also compared the HMD and a flat monitor as experimental devices. METHODS: Forty participants were recruited for the current study (Study 1: 20 participants with the HMD device; Study 2: 20 participants with the flat monitor). They navigated a virtual room as a first-person viewer and used environmental landmarks to remember their spatial position and orientation. The main dependent measures were working memory error, reference memory error, detection time, travel distance, and participant’s head movements. To validate the program, participants also conducted neuropsychological assessments and self-reported measures. RESULTS: The results for HMD-RAM tasks were consistent with the results of previous research conducted on animals, and the HMD elicited a higher sense of presence, immersion, and simulator sickness than the flat monitor. According to post-experiment questions on navigation strategy, creating landmarks was important when people were discovering locations in their environment, and an HMD was beneficial for better navigation strategy. CONCLUSION: These results suggest that the HMD-RAM is valuable for estimating spatial learning and memory in humans and may be a useful tool for early diagnosis of deficits in spatial learning and memory, including amnestic mild cognitive impairment and Alzheimer’s disease.
Animals ; Arm* ; Early Diagnosis ; Head Movements ; Humans ; Immersion ; Memory* ; Memory, Short-Term ; Mild Cognitive Impairment ; Models, Animal ; Spatial Learning* ; Spatial Memory

BACKGROUND: Numerous condylar repositioning methods have been reported. However, most of them are 2-dimensional or are complex procedures that require a longer operation time and a highly trained surgeon. This study aims to introduce a new technique using a condylar repositioning plate and a centric relation splint to achieve a centric relationship. METHODS: We evaluated 387 patients who had undergone surgery for skeletal jaw deformities. During the operation, a centric relation splint, intermediate splint, final centric occlusion splint, and condylar repositioning plate along with an L-type mini-plate for LeFort I osteotomy or a bicortical screw for bilateral sagittal split ramus osteotomy were utilized for rigid fixation. The evaluation included: a physical examination to detect preoperative and postoperative temporomandibular joint dysfunction, 3-dimensional computed tomography and oblique transcranial temporomandibular joint radiography to measure 3-dimensional condylar head movement, and posteroanterior and lateral cephalometric radiography to measure the preoperative and postoperative movement of the bony segment and relapse rate. RESULTS: A 0.3% relapse rate was observed in the coronal plane, and a 2.8% relapse rate in the sagittal plane, which is indistinguishable from the dental relapse rate in orthodontic treatment. The condylar repositioning plate could not fully prevent movement of the condylar head, but the relapse rate was minimal, implying that the movement of the condylar head was within tolerable limits. CONCLUSIONS: Our condylar repositioning method using a centric relation splint and mini-plate in orthognathic surgery was found to be simple and effective for patients suffering from skeletal jaw deformities.
Centric Relation ; Congenital Abnormalities ; Head ; Head Movements ; Humans ; Jaw ; Methods ; Orthognathic Surgery ; Osteotomy ; Osteotomy, Le Fort ; Osteotomy, Sagittal Split Ramus ; Physical Examination ; Radiography ; Recurrence* ; Splints ; Temporomandibular Joint

Bilateral vestibular deficit affects far fewer patients than unilateral deficit, and thus has been understudied. When bilateral vestibular organs are injured, loss of input of vestibulo-ocular and vestibulo-spinal reflex that normally stabilize the eyes and body, affected patients suffer blurred vision during head movement, postural instability, and disequilibrium. Vestibular rehabilitation therapy is an exercise-based treatment program designed to promote vestibular adaptation and substitution. The rationale for the exercises, which originated from the observation that patients who were active recovered faster, was based on the supposition that the head movements that provoke the patient's dizziness play an important role in hastening the recovery process. Here the author reviews the clinical manifestation and treatment of bilateral vestibular deficit that include vestibular rehabilitation therapy and vestibular device that studied today.
Dizziness ; Exercise ; Head Movements ; Humans ; Reflex ; Rehabilitation ; Vertigo ; Vestibular Diseases

BACKGROUND: The proper cuff pressure is important to prevent complications related to the endotracheal tube (ETT). We evaluated the change in ETT cuff pressure by changing the position from supine to prone without head movement. METHODS: Fifty-five patients were enrolled and scheduled for lumbar spine surgery. Neutral angle, which was the angle on the mandibular angle between the neck midline and mandibular inferior border, was measured. The initial neutral pressure of the ETT cuff was measured, and the cuff pressure was subsequently adjusted to 26 cmH2O. Flexed or extended angles and cuff pressure were measured in both supine and prone positions, when the patient's head was flexed or extended. Initial neutral pressure in prone was compared with adjusted neutral pressure (26 cmH2O) in supine. Flexed and extended pressure were compared with adjusted neutral pressure in supine or prone, respectively. RESULTS: There were no differences between supine and prone position for neutral, flexed, and extended angles. The initial neutral pressure increased after changing position from supine to prone (26.0 vs. 31.5 +/- 5.9 cmH2O, P < 0.001). Flexed and extended pressure in supine were increased to 38.7 +/- 6.7 (P < 0.001) and 26.7 +/- 4.7 cmH2O (not statistically significant) than the adjusted neutral pressure. Flexed and extended pressure in prone were increased to 40.5 +/- 8.8 (P < 0.001) and 29.9 +/- 8.7 cmH2O (P = 0.002) than the adjusted neutral pressure. CONCLUSIONS: The position change from supine to prone without head movement can cause a change in ETT cuff pressure.
Head Movements ; Head* ; Humans ; Neck ; Prone Position ; Spine