1. Eye movements were recorded in four rhesus monkeys, before and after bilateral ablations of the flocculi and portions of the paraflocculi (“flocculectomy”). Animals were trained to fixate and follow targets so that pursuit, saccades, and vestibular and optokinetic nystagmus could be quantitated. 2. The vestibuloocular reflex (VOR) was mildly affected by flocculectomy. In darkness the VOR gain (eye velocity/head velocity) for steps of head velocity (normal range, 0.84-0.96) increased postoperatively in one monkey to 1.17, decreased in another to 0.62, and did not change significantly in the other two (0.96, 0.94). VOR phase lead at 0.05-Hz oscillation in darkness (normal range, O,O--LOO) increased in two monkeys by 12 and 9.5 O but did not change significantly in the others. 3. Visual suppression of inappropriate vestibular nystagmus was impaired. During oscillation at 0.25 Hz with a head-fixed visual scene, the average amount of attenuation of the VOR decreased from 5 1% preoperatively to 20% postoperatively. Visual suppression of caloric nystagmus was comparably affected. 4. Smooth tracking of small targets moving in space was impaired either with the head still (smooth pursuit) or moving (cancellation of the VOR by fixating a target rotating with the head). The average gain (gaze velocity/target velocity) in either case was about 0.65 (normal, 0.95-0.98). The pursuit deficit was less than that reported after total cerebellectomy, suggesting other cerebellar structures also participate in smooth tracking. 5. Optokinetic nystagmus (OKN) was present postoperatively but, in response to a constant-velocity stimulus, the initial slowphase velocity decreased by 50% and the rise time to a steady state nearly doubled. For stimuli belowr 6O”/s the average steady-state gain was only mildly diminished to 0.86 (normal, 0.98) and the time course of optokinetic afternystagmus (OKAN) in darkness was normal. The response to higher velocity optokinetic stimuli was impaired. These abnormalities can largely be attributed to the coexisting pursuit deficit although the protracted rise to a steady state suggests a change in the ability of the brain stem optokinetic system to handle large amounts of retinal slip. 6. Flocculectomized monkeys showed horizontally, gaze-paretic nystagmus with exponentially decaying centripetal drift (time constant, 1.56 s) and vertically, downbeat nystagmus with exponentially decaying (in three monkeys) or exponentially increasing (in one monkey) slow phases. All animals showed rebound nystagmus. These results implicate the flocculus and possibly the paraflocculus in the control of the time constant and stability of the brain stem oculomotor integrators. 7. Saccadic velocities and accuracy were normal but flocculectomized monkeys showed brief (40150 ms duration), approximately exponential, postsaccadic drift with amplitudes up to 15% of the size of the saccade. The eyes usually drifted in the same direction as the saccade but each monkey showed an idiosyncratic pattern depending on saccade direction and eye position. Postsaccadic drift may reflect a mismatch between the phasic (pulse) and tonic (step) innervational changes that create saccades.

Effects of ablation of flocculus and paraflocculus of eye movements in primate

Tumors and tumorous conditions of the bones and joints

1 Introduction.- 2 Peripheral Morphology.- 3 Biophysics of the Peripheral End Organs.- 4 Mechanoneural Transduction and the Primary Afferent Response.- 5 Labyrinthine Input to the Vestibular Nuclei and Reticular Formation.- 6 The Vestibular System and the Cerebellum.- 7 The Vestibulospinal System.- 8 The Vestibuloocular System.- References.

Mammalian Vestibular Physiology

Providing a solid foundation in second language acquisition, this book has become the leading introduction to the subject for students of linguistics, psychology and education, and trainee language teachers. Now in its third edition, the textbook offers comprehensive coverage of fundamental concepts, including second language acquisition (SLA) in adults and children, in formal and informal learning contexts, and in diverse socio-cultural settings, and takes an interdisciplinary approach, encouraging students to consider SLA from linguistic, psychological and social perspectives. Each chapter contains a list of key terms, a summary, and a range of graded exercises suitable for self-testing and class discussion. The third edition has been revised throughout, and features new material on the practical aspects of teaching language, along with updated online resources, including new classroom activities to accompany each chapter, as well as updated references and further reading suggestions.

https://repository.bbg.ac.id/bitstream/588/1/Introducing_Second_Language_Acquisition_.pdf

Introducing Second Language Acquisition

The sensation of self-motion is a common visual illusion which allows inferences concerning visual-vestibular interaction. It may be perceived while gazing at moving clouds, streaming water, or when a train moves on the adjacent track in a railway station. This compelling sensation of body movement can even affect postural balance. On first approaching the problem, a psychologic explanation could be suggested in the sense of Helmholtz’s (1896) Urteilstauschung. One might assume that these illusions are inferences based upon the conscious or unconscious assumption of a stable environment, so that when the environment does in fact move, the observer infers that he himself is moving. This interpretation would be consistent with the individual’s past experience as the entire visual surround seldom moves uniformly under natural conditions unless the body moves relative to the earth.

Visual-Vestibular Interaction: Effects on Self-Motion Perception and Postural Control

Twelve members of a family with hereditary cerebellar ataxia of late onset were examined and, in 5, quantitative recording of eye movements were obtained. The initial and most severe symptom in all patients was ataxia of gait, followed by dysarthria and later by dysmetria of the limbs. Clinical examination did not reveal involvement of structures other than the cerebellum. Ocular motor examination showed: (1) inability to hold eccentric gaze resulting in gaze-paretic nystagmus; (2) downward beating nystagmus, accentuated on lateral gaze; (3) defective smooth pursuit, with relative preservation of optokinetic nystagmus induced by full-field stimulation; (4) rebound nystagmus; (5) enhanced gain (eye velocity/head velocity) of the vestibulo-ocular reflex during rotation in darkness; (6) decreased ability to suppress the vestibulo-ocular reflex during fixation of an object rotating with the patient; (7) saccadic dysmetria, especially downward overshoot; and (8) square wave-jerks. Although each of these signs can probably occur with lesions elsewhere in the brain, in combination they are highly suggestive of cerebellar involvement. With the reservation that we do not yet have pathological confirmation of the location of our patients' lesions, our results support the suggestion that the cerebellum specifically: (1) helps maintain eccentric gaze; (2) produces smooth pursuit eye movements; and (3) modulates the amplitude of saccadic eye movements. Many of the characteristics of the altered vestibulo-ocular responses and rebound nystagmus could be explained by the underlying anomaly in the smooth pursuit system.

Ocular motor abnormalities in hereditary cerebellar ataxia

Objectives To characterize the pathogenesis and clinical features of optic disc edema associated with obstructive sleep apnea syndrome (SAS). Methods A series of 4 patients with SAS and papilledema (PE) underwent complete neuro-ophthalmologic evaluation and lumbar puncture. In 1 patient, continuous 24-hour intracranial pressure (ICP) monitoring was also performed. Results All 4 patients had bilateral PE that was asymmetric in 2. Three patients had optic nerve dysfunction, asymmetric in 1, unilateral in 2. Daytime cerebrospinal fluid pressure measurements were within normal range. Nocturnal monitoring performed in one patient, however, demonstrated repeated episodes of marked ICP elevation associated with apnea and arterial oxygen desaturation. Conclusions We propose that PE in SAS is due to episodic nocturnal hypoxemia and hypercarbia resulting in increased ICP secondary to cerebral vasodilation. In these individuals, intermittent ICP elevation is sufficient to cause persistent disc edema. These patients may be at increased risk for developing visual loss secondary to PE compared with patients with obesity-related pseudotumor cerebri because of associated hypoxemia. The diagnosis of SAS PE may not be appreciated because daytime cerebrospinal fluid pressure measurements are normal and because patients tend to present with visual loss rather than with symptoms of increased ICP.

https://jamanetwork.com/journals/jamaophthalmology/articlepdf/413919/ecs90282.pdf

Papilledema and obstructive sleep apnea syndrome.

Optokinetic responses in labyrinthine-defective human beings.

Congenital ocular motor apraxia

BACKGROUND: There have been anecdotal reports of anterior ischemic optic neuropathy (AION) occurring in eyes with optic disc drusen (ODD), but the clinical features of this condition have not been well characterized. OBJECTIVES: To better describe the clinical features of AION associated with ODD and to compare the clinical features of this condition with those of "garden variety" nonarteritic AION. METHODS: We reviewed the medical records of 20 patients who experienced an episode of AION in an eye with ODD. In 4 patients, both eyes were affected; thus, 24 eyes were studied. The diagnosis of ODD was made by ophthalmoscopic identification, orbital ultrasonography, or computed tomographic scanning. We recorded age, sex, vascular risk factors, symptoms, visual acuity, visual fields, and results of the follow-up examination in all patients. These findings were compared with data from previously reported series of patients with nonarteritic AION. RESULTS: Our 20 patients included 14 men and 6 women (age range, 18-69 years; mean, 49.4 years). Vascular risk factors were identified in 10 patients (50%). Three patients reported episodes of transient visual loss before their fixed deficit. The visual acuity at the initial examination was 20/60 or better in 15 (62%) of the 24 eyes; 8 had a visual acuity of 20/20. The predominant pattern of visual field loss was an altitudinal or arcuate defect in 19 (79%) and a centrocecal scotoma in 5 (21%) of the 24 eyes. There was subjective worsening of vision before the initial neuro-ophthalmic examination in 11 eyes (46%) and objective documentation of progression in 7 eyes (29%). The final visual acuity was 20/40 or better in 13 (62%) of 21 eyes and 20/200 or worse in 3 (14%) of 21 eyes. CONCLUSIONS: Our patients were strikingly similar to those with nonarteritic AION unassociated with drusen in regard to prevalence of vascular risk factors, pattern of visual field loss, and occurrence of a subsequent similar event in the fellow eye. In contrast, however, patients with ODD-AION were younger than those with nonarteritic AION, were more likely to report preceding episodes of transient visual obscuration, and enjoyed a more favorable visual outcome.

https://jamanetwork.com/journals/jamaophthalmology/articlepdf/416032/ecs30044.pdf

Robert D. Yee

Papers

Ocular motor abnormalities in hereditary cerebellar ataxia

Papilledema and obstructive sleep apnea syndrome.

Optokinetic responses in labyrinthine-defective human beings.

Congenital ocular motor apraxia

Anterior Ischemic Optic Neuropathy in Eyes With Optic Disc Drusen