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

BACKGROUND AND OBJECTIVES: Dizzy patients with abnormal otolith function tests, despite a normal caloric response, are defined as having specific (isolated) otolith organ dysfunction. This study was performed to compare the differences in clinical presentation between isolated otolith dysfunction (iOD) patients with lab- and Sx-based iOD group and lab-based iOD symptoms. SUBJECTS AND METHODS: The medical records of 23 iOD patients with normal caloric response but abnormal cervical vestibular evoked myogenic potential (VEMP), ocular VEMP, or subjective visual vertical were reviewed. Non-spinning vertigo was considered as otolith-related symptoms. The patients’ age, onset of dizziness, Numeric Rating Scale on the severity of dizziness, and concomitant vestibular disorders were analyzed. RESULTS: Patients in the lab-based iOD group were significantly older than those in the lab- and Sx-based iOD group. Known vestibular disorders were significantly more common in the lab-based iOD group (83.3%) compared to the lab- and Sx-based iOD group (18.2%). Despite the normal caloric response, catch-up saccade was found in the video head impulse test in more than half (54.5%) of the lab-based iOD group patients. There was no catch-up saccade in the lab- and Sx-based iOD group. There were no significant differences in gender ratio, frequency of dizziness attacks, and duration of illness. CONCLUSIONS: We propose new definitions of definite iOD (lab- and Sx-based iOD) and probable iOD (lab- or Sx-based iOD). These new definitions may help researchers to identify patients who are more likely to have true iOD, and facilitate comparisons of results between different studies.
Dizziness ; Head Impulse Test ; Humans ; Medical Records ; Otolaryngology ; Otolithic Membrane ; Saccades ; Vertigo

BACKGROUND AND PURPOSE: Conflicting results about vestibular function in progressive supranuclear palsy (PSP) prompted a systematic examination of the semicircular canal function, otolith function, and postural stability. METHODS: Sixteen patients with probable PSP [9 females, age=72±6 years (mean±SD), mean disease duration=3.6 years, and mean PSP Rating Scale score=31] and 17 age-matched controls were examined using the video head impulse test, caloric testing, ocular and cervical vestibular evoked myogenic potentials (o- and cVEMPs), video-oculography, and posturography. RESULTS: There was no evidence of impaired function of the angular vestibulo-ocular reflex (gain=1.0±0.1), and caloric testing also produced normal findings. In terms of otolith function, there was no significant difference between PSP patients and controls in the absolute peakto-peak amplitude of the oVEMP (13.5±7.2 µV and 12.5±5.6 µV, respectively; p=0.8) or the corrected peak-to-peak amplitude of the cVEMP (0.6±0.3 µV and 0.5±0.2 µV, p=0.3). The total root-mean-square body sway was significantly increased in patients with PSP compared to controls (eyes open/head straight/hard platform: 9.3±3.7 m/min and 6.9±2.1 m/min, respectively; p=0.032). As expected, the saccade velocities were significantly lower in PSP patients than in controls: horizontal, 234±92°/sec and 442±66°/sec, respectively; downward, 109±105°/sec and 344±72°/sec; and upward, 121±110°/sec and 348±78°/sec (all p<0.01). CONCLUSIONS: We found no evidence of impairment of either high- or low-frequency semicircular function or otolith organ function in the examined PSP patients. It therefore appears that other causes such as degeneration of supratentorial pathways lead to postural imbalance and falls in patients with PSP.
Accidental Falls ; Caloric Tests ; Female ; Head Impulse Test ; Humans ; Movement Disorders ; Otolithic Membrane ; Reflex, Vestibulo-Ocular ; Saccades ; Semicircular Canals ; Supranuclear Palsy, Progressive ; Tauopathies ; Vestibular Evoked Myogenic Potentials

Abnormal eye movements are commonly observed in movement disorders. Ocular motility examination should include bedside evaluation and laboratory recording of ocular misalignment, involuntary eye movements, including nystagmus and saccadic intrusions/oscillations, triggered nystagmus, saccades, smooth pursuit (SP), and the vestibulo-ocular reflex. Patients with Parkinson's disease (PD) mostly show hypometric saccades, especially for the self-paced saccades, and impaired SP. Early vertical saccadic palsy is characteristic of progressive supranuclear palsy-Richardson's syndrome. Patients with cortico-basal syndrome typically show a delayed onset of saccades. Downbeat and gaze-evoked nystagmus and hypermetric saccades are characteristic ocular motor findings in ataxic disorders due to cerebellar dysfunction. In this review, we discuss various ocular motor findings in movement disorders, including PD and related disorders, ataxic syndromes, and hyperkinetic movement disorders. Systemic evaluation of the ocular motor functions may provide valuable information for early detection and monitoring of movement disorders, despite an overlap in the abnormal eye movements among different movement disorders.
Ataxia ; Cerebellar Diseases ; Eye Movements ; Humans ; Hyperkinesis ; Movement Disorders ; Paralysis ; Parkinson Disease ; Parkinsonian Disorders ; Pursuit, Smooth ; Reflex, Vestibulo-Ocular ; Saccades