Multiple system atrophy （MSA） is a rare degenerative disease of the nervous system and has diverse and atypical clinical manifestations， and it overlaps with other diseases in α-synuclein spectrum disease. There are great challenges in the diagnosis and early differential diagnosis of the disease， and missed diagnosis and misdiagnosis occur from time to time， thereby delaying the treatment of the disease.Videonystagmography （VNG） is currently the main noninvasive test used to assess vestibular function and can provide different eye movement parameters. Studies have shown the presence of abnormal eye movements in patients with MSA. From the perspective of vision-eye movement， this article reviews the current status of research on eye movements in patients with MSA and reveals the internal connection between them， in order to provide an important reference for the early diagnosis of MSA.
Saccades

While multiple step saccades (MSS) are occasionally reported in the healthy population, they are more evident in patients with Parkinson's disease (PD). Therefore, MSS has been suggested as a biological marker for the diagnosis of PD. However, the lack of clarity on the neural mechanism underlying the generation of MSS largely impedes their application in the clinic. We have proposed recently that MSS are triggered by the discrepancy between desired and executed saccades. Accordingly, brain regions involved in saccadic planning and execution might play a role in the generation of MSS. To test this hypothesis, we explored the role of the prefrontal (PFC) and posterior parietal cortex (PPC) in generating MSS by conducting two experiments: electroencephalographic recording and single-pulse transcranial magnetic stimulation in the PFC or PPC of humans while participants were performing a gap saccade task. We found that the PFC and PPC are involved in the generation of MSS.
Humans ; Parietal Lobe/physiology* ; Saccades/physiology* ; Prefrontal Cortex/physiology* ; Male ; Transcranial Magnetic Stimulation ; Female ; Electroencephalography ; Adult ; Young Adult

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

Recent work in decision neuroscience suggests that visual saliency can interact with reward-based choice, and the lateral intraparietal cortex (LIP) is implicated in this process. In this study, we recorded from LIP neurons while monkeys performed a two alternative choice task in which the reward and luminance associated with each offer were varied independently. We discovered that the animal's choice was dictated by the reward amount while the luminance had a marginal effect. In the LIP, neuronal activity corresponded well with the animal's choice pattern, in that a majority of reward-modulated neurons encoded the reward amount in the neuron's preferred hemifield with a positive slope. In contrast, compared to their responses to low luminance, an approximately equal proportion of luminance-sensitive neurons responded to high luminance with increased or decreased activity, leading to a much weaker population-level response. Meanwhile, in the non-preferred hemifield, the strength of encoding for reward amount and luminance was positively correlated, suggesting the integration of these two factors in the LIP. Moreover, neurons encoding reward and luminance were homogeneously distributed along the anterior-posterior axis of the LIP. Overall, our study provides further evidence supporting the neural instantiation of a priority map in the LIP in reward-based decisions.
Animals ; Macaca mulatta/physiology* ; Parietal Lobe ; Neurons/physiology* ; Saccades ; Reward ; Photic Stimulation

The superior colliculus (SC), one of the most well-characterized midbrain sensorimotor structures where visual, auditory, and somatosensory information are integrated to initiate motor commands, is highly conserved across vertebrate evolution. Moreover, cell-type-specific SC neurons integrate afferent signals within local networks to generate defined output related to innate and cognitive behaviors. This review focuses on the recent progress in understanding of phenotypic diversity amongst SC neurons and their intrinsic circuits and long-projection targets. We further describe relevant neural circuits and specific cell types in relation to behavioral outputs and cognitive functions. The systematic delineation of SC organization, cell types, and neural connections is further put into context across species as these depend upon laminar architecture. Moreover, we focus on SC neural circuitry involving saccadic eye movement, and cognitive and innate behaviors. Overall, the review provides insight into SC functioning and represents a basis for further understanding of the pathology associated with SC dysfunction.
Superior Colliculi/physiology* ; Saccades ; Neurons/physiology*

Biomechanical Phenomena ; Eye Movements ; Neurons/physiology* ; Pursuit, Smooth ; Saccades

Active exploratory behaviors have often been associated with theta oscillations in rodents, while theta oscillations during active exploration in non-human primates are still not well understood. We recorded neural activities in the frontal eye field (FEF) and V4 simultaneously when monkeys performed a free-gaze visual search task. Saccades were strongly phase-locked to theta oscillations of V4 and FEF local field potentials, and the phase-locking was dependent on saccade direction. The spiking probability of V4 and FEF units was significantly modulated by the theta phase in addition to the time-locked modulation associated with the evoked response. V4 and FEF units showed significantly stronger responses following saccades initiated at their preferred phases. Granger causality and ridge regression analysis showed modulatory effects of theta oscillations on saccade timing. Together, our study suggests phase-locking of saccades to the theta modulation of neural activity in visual and oculomotor cortical areas, in addition to the theta phase locking caused by saccade-triggered responses.
Animals ; Frontal Lobe/physiology* ; Macaca mulatta ; Neurons/physiology* ; Saccades ; Theta Rhythm ; Visual Fields

OBJECTIVES: Suppression head impulse paradigm (SHIMP) in video head impulse test is now newly used to test vestibular function. The aim of this study was to analyze normative values of SHIMP for healthy Korean subjects in each decade of life. METHODS: SHIMP and HIMP responses were measured with the video head impulse test in 70 healthy subjects. Vestibulo-ocular reflex gain and anticompensatory saccade were analyzed and compared at each decade of life. RESULTS: All subjects produced anticompensatory saccades in SHIMP. Gain values did not vary significantly with age. Gain values in SHIMP were lower than gain values in HIMP. The gain values of rightward impulse were higher than the gain values of leftward impulse. CONCLUSIONS: Gain values and anticompensatory saccades in SHIMP were consistently equal in each decade of life. Normative values of SHIMP seems largely unaffected by aging.
Aging ; Head ; Head Impulse Test ; Healthy Volunteers ; Reflex, Vestibulo-Ocular ; Saccades

Myasthenia gravis (MG) is an autoimmune disease caused by autoantibodies to the acetylcholine receptors of the neuromuscular junction characterized by weakness and abnormal fatigability of the muscles. Therefore, the diagnosis of MG depends on the recognition of this distinctive pattern of fatigable weakness. Previous studies presented the diagnostic efficacy of saccadic eye movements in patients with ocular MG. We here in report 2 patients of ocular MG showing the fatigue effects during repetitive sustained smooth pursuit, and the effects of the administration of edrophonium on myasthenic smooth pursuit. Changes in smooth pursuits reflecting peripheral and secondary central mechanisms were demonstrated.
Autoantibodies ; Autoimmune Diseases ; Diagnosis ; Edrophonium ; Fatigue ; Humans ; Muscles ; Myasthenia Gravis ; Neuromuscular Junction ; Pursuit, Smooth ; Receptors, Cholinergic ; Saccades

OBJECTIVES: To investigate the impact of labyrinthectomy and intratympanic (IT) gentamicin injections on the contralateral labyrinth, we also assessed the response of each individual semicircular canal to each IT gentamicin application. METHODS: We performed a pilot observational study on tertiary, referral, academic settings. Thirteen patients with unilateral vestibular pathology were organized into two groups, group I (seven patients) receiving IT gentamicin and group II undergoing labyrinthectomy (six patients). All patients underwent six-canal video-head-impulse test in predetermined time intervals. Patients receiving gentamicin were additionally tested 3 to 5 days after every sequential injection, until all ipsilateral canals were ablated, to determine the order of response to gentamicin. We recorded the vestibular-ocular reflex gains and the presence of covert/overt saccades for each canal. RESULTS: The posttreatment ipsilateral gains were abnormal. No patient from the gentamicin group developed abnormal contralateral responses, while patients undergoing labyrinthectomy had abnormal contralateral responses from at least one canal, even several months posttreatment. Finally, the lateral semicircular canal was the first one to be affected by IT gentamicin followed by the posterior canal: the superior canal was ablated last. CONCLUSION: In our study, labyrinthectomy had an impact on the responses recorded from the contralateral ear, while IT gentamicin ablated the ipsilateral labyrinthine function without affecting the contralateral responses, possibly because of a milder, more gradual impact. We also show for the first time the order that IT gentamicin application affects the semicircular canals, with the lateral being the first to be affected.
Ear ; Ear, Inner ; Gentamicins ; Head Impulse Test ; Humans ; Observational Study ; Pathology ; Referral and Consultation ; Reflex ; Saccades ; Semicircular Canals