The relationships between eye movements and head movements of the primate during gaze shifts are analyzed in detail in the present paper. Applying the mechanisms of neurophysiology to engineering domain, we have improved the robot eye-head coordination. A bionic control strategy of coordinated head-eye motion was proposed. The processes of gaze shifts are composed of an initial fast phase followed by a slow phase. In the fast phase saccade eye movements and slow head movements were combined, which cooperate to bring gaze from an initial resting position toward the new target rapidly, while in the slow phase the gaze stability and target fixation were ensured by the action of the vestibulo-ocular reflex (VOR) where the eyes and head rotate by equal amplitudes in opposite directions. A bionic gaze control model was given. The simulation results confirmed the effectiveness of the model by comparing with the results of neurophysiology experiments.
Bionics ; Eye Movements ; physiology ; Fixation, Ocular ; physiology ; Head Movements ; physiology ; Humans ; Ocular Physiological Phenomena ; Orientation ; Photic Stimulation ; Reflex, Vestibulo-Ocular ; physiology ; Saccades ; physiology

BACKGROUNDReading Chinese, a kind of ideogram, relies more on visual cognition. The visuospatial cognitive deficit of Chinese dyslexia is an interesting topic that has received much attention. The purpose of current research was to explore the visuopatial cognitive characteristics of Chinese dyslexic children by studying their eye movements via a picture searching test.

METHODSAccording to the diagnostic criteria defined by ICD-10, twenty-eight dyslexic children (mean age (10.12 +/- 1.42) years) were enrolled from the Clinic of Children Behavioral Disorder in the third affiliated hospital of Sun Yat-sen University. And 28 normally reading children (mean age (10.06 +/- 1.29) years), 1:1 matched by age, sex, grade and family condition were chosen from an elementary school in Guangzhou as a control group. Four groups of pictures (cock, accident, canyon, meditate) from Picture Vocabulary Test were chosen as eye movement experiment targets. All the subjects carried out the picture searching task and their eye movement data were recorded by an Eyelink II High-Speed Eye Tracker. The duration time, average fixation duration, average saccade amplitude, fixation counts and saccade counts were compared between the two groups of children.

RESULTSThe dyslexic children had longer total fixation duration and average fixation duration (F = 7.711, P < 0.01; F = 4.520, P < 0.05), more fixation counts and saccade counts (F = 7.498, P < 0.01; F = 11.040, P < 0.01), and a smaller average saccade amplitude (F = 29.743, P < 0.01) compared with controls. But their performance in the picture vocabulary test was the same as those of the control group. The eye movement indexes were affected by the difficulty of the pictures and words, all eye movement indexes, except saccade amplitude, had a significant difference within groups (P < 0.05).

CONCLUSIONSChinese dyslexic children have abnormal eye movements in picture searching, applying slow fixations, more fixations and small and frequent saccades. Their abnormal eye movement mode reflects the poor ability and strategy of visual information processing.

Child ; Cognition ; Dyslexia ; physiopathology ; psychology ; Eye Movements ; Female ; Fixation, Ocular ; Humans ; Intelligence Tests ; Male ; Saccades

Creutzfeldt-Jakob disease (CJD) is a human prion disease with rapidly progressive neurodegeneration. The major clinical manifestations of CJD include mental deterioration, myoclonus, cerebellar dysfunction, and neuro-ophthalmic symptoms and signs. However, abnormal eye movements as an early sign of CJD are rare. We report a 49-year-old man with periodic alternating nystagmus in early disease course.
Cerebellar Diseases ; Creutzfeldt-Jakob Syndrome ; Eye Movements ; Fixation, Ocular ; Humans ; Middle Aged ; Myoclonus ; Nystagmus, Pathologic ; Prion Diseases

A 51-year-old woman with breast cancer presented with progressive diplopia. Neuro-ophthalmologic examination revealed right gaze palsy and peripheral facial nerve palsy. Brain magnetic resonance imaging (MRI) was normal. However, two months later a repeat brain MRI revealed an enhancing round nodular mass at the right facial colliculus of the lower pons, at the location of the abducens nucleus. Localized metastasis to the abducens nucleus can cause gaze palsy in a patient with breast cancer.
*Abducens Nerve Diseases ; Breast Neoplasms/*pathology ; Cranial Nerve Neoplasms/*complications/*secondary ; Facial Paralysis/complications ; Female ; Fixation, Ocular ; Humans ; Magnetic Resonance Imaging ; Middle Aged ; Ocular Motility Disorders/*etiology/physiopathology ; Pons/pathology

Joubert syndrome and Joubert syndrome-related disorders (JSRDs) are rare autosomal recessive or X-linked disorders characterized by cerebellar vermis hypoplasia and a brain stem malformation, which presents as the “molar tooth sign” in magnetic resonance imaging (MRI). JSRDs are a group of clinically heterogeneous conditions that exhibit neurological manifestations and multiple organ involvement. JSRDs are also genetically heterogeneous, and approximately 20 causative genes that account for 45% of JSRDs have been identified. A 7-yr-old boy visited Wonkwang University Sanbon Hospital with the following presentations: no ocular fixation, ataxia, growth retardation, and hypotonia. Physical examination revealed facial dysmorphism, spindle shaped fingers, and height (99 cm) and weight (13 kg) below the third percentile. Ophthalmic examination revealed retinal dystrophy. A diagnosis of JSRDs was made based on clinical and brain MRI findings. We found two heterozygous variants c.2945 G>T; p.Arg982Met (G>T) and c.2216dupA; p.Phe740Valfs*2 (dupA) in AHI1, and a heterozygous c.3973C>T; p.Arg1325Trp (C>T) variant in KIF7 by whole exome sequencing (WES). Genetic analysis on the proband's father revealed that he had both AHI1 variants, but did not have the KIF7 variant, which was inconsistent with autosomal recessive inheritance. Therefore, the G>T variant and C>T variant were presumed to be of “uncertain significance.” Furthermore, one novel dupA variant was interpreted as “pathogenic,” while the second allele was not detected. Caution should be exercised while interpreting the significance of variants detected by WES. In addition, the involvement of genes other than the 20 known ones will require further investigation to elucidate the pathogenesis of JSRDs.
Alleles ; Ataxia ; Brain ; Brain Stem ; Cerebellar Vermis ; Child* ; Diagnosis ; Exome* ; Fathers ; Fingers ; Fixation, Ocular ; Humans ; Magnetic Resonance Imaging ; Male ; Muscle Hypotonia ; Neurologic Manifestations ; Physical Examination ; Retinal Dystrophies ; Tooth ; Wills

We report a case of early resolution of convergence spasms following the addition of antipsychotic medications and present it as a possible alternative to the conventional treatment for convergence spasms. The cessation of atropinization of the eyes and the use of reading glasses was achieved after only 2 months following the initiation of antipsychotic medications for childhood emotional disorder.
Affective Symptoms/*drug therapy ; Anti-Anxiety Agents/therapeutic use ; Antipsychotic Agents/*therapeutic use ; Child ; Diazepam/therapeutic use ; E ; Female ; Fixation, Ocular ; Humans ; Serotonin Uptake Inhibitors/therapeutic use ; Sertraline/therapeutic use ; Treatment Outcome ; Visual Acuity

Visual fixation is an item in the visual function subscale of the Coma Recovery Scale-Revised (CRS-R). Sometimes clinicians using the behavioral scales find it difficult to detect because of the motor impairment in patients with disorders of consciousness (DOCs). Brain-computer interface (BCI) can be used to improve clinical assessment because it directly detects the brain response to an external stimulus in the absence of behavioral expression. In this study, we designed a BCI system to assist the visual fixation assessment of DOC patients. The results from 15 patients indicated that three showed visual fixation in both CRS-R and BCI assessments and one did not show such behavior in the CRS-R assessment but achieved significant online accuracy in the BCI assessment. The results revealed that electroencephalography-based BCI can detect the brain response for visual fixation. Therefore, the proposed BCI may provide a promising method for assisting behavioral assessment using the CRS-R.
Adolescent ; Adult ; Aged ; Brain ; physiopathology ; Brain-Computer Interfaces ; Consciousness Disorders ; diagnosis ; physiopathology ; Diagnosis, Computer-Assisted ; methods ; Electroencephalography ; methods ; Evoked Potentials ; Female ; Fixation, Ocular ; physiology ; Humans ; Male ; Middle Aged ; Neurologic Examination ; Pilot Projects ; Severity of Illness Index ; User-Computer Interface