scholarly journals Vergence eye movements are not essential for stereoscopic depth

2014 ◽  
Vol 281 (1776) ◽  
pp. 20132118 ◽  
Author(s):  
Arthur J. Lugtigheid ◽  
Laurie M. Wilcox ◽  
Robert S. Allison ◽  
Ian P. Howard
Keyword(s):  
Eye Movements ◽  
Depth Perception ◽  
Conclusive Evidence ◽  
Stereoscopic Depth ◽  
Direct Process ◽  
Retinal Disparity ◽  
Strong Link ◽  
Complex Interactions ◽  
Retinal Input ◽  
The Brain

The brain receives disparate retinal input owing to the separation of the eyes, yet we usually perceive a single fused world. This is because of complex interactions between sensory and oculomotor processes that quickly act to reduce excessive retinal disparity. This implies a strong link between depth perception and fusion, but it is well established that stereoscopic depth percepts are also obtained from stimuli that produce double images. Surprisingly, the nature of depth percepts from such diplopic stimuli remains poorly understood. Specifically, despite long-standing debate it is unclear whether depth under diplopia is owing to the retinal disparity (directly), or whether the brain interprets signals from fusional vergence responses to large disparities (indirectly). Here, we addressed this question using stereoscopic afterimages, for which fusional vergence cannot provide retinal feedback about depth. We showed that observers could reliably recover depth sign and magnitude from diplopic afterimages. In addition, measuring vergence responses to large disparity stimuli revealed that that the sign and magnitude of vergence responses are not systematically related to the target disparity, thus ruling out an indirect explanation of our results. Taken together, our research provides the first conclusive evidence that stereopsis is a direct process, even for diplopic targets.

Updating Target Distance Across Eye Movements in Depth

2008 ◽  
Vol 99 (5) ◽  
pp. 2281-2290 ◽  
Author(s):  
Stan Van Pelt ◽  
W. Pieter Medendorp
Keyword(s):  
Eye Movements ◽  
Eye Movement ◽  
Gaze Shift ◽  
Retinal Disparity ◽  
Distance Information ◽  
The Moment ◽  
Depth Constancy ◽  
The Brain ◽  
Target Depth ◽  
Vergence Eye Movement

We tested between two coding mechanisms that the brain may use to retain distance information about a target for a reaching movement across vergence eye movements. If the brain was to encode a retinal disparity representation (retinal model), i.e., target depth relative to the plane of fixation, each vergence eye movement would require an active update of this representation to preserve depth constancy. Alternatively, if the brain was to store an egocentric distance representation of the target by integrating retinal disparity and vergence signals at the moment of target presentation, this representation should remain stable across subsequent vergence shifts (nonretinal model). We tested between these schemes by measuring errors of human reaching movements ( n = 14 subjects) to remembered targets, briefly presented before a vergence eye movement. For comparison, we also tested their directional accuracy across version eye movements. With intervening vergence shifts, the memory-guided reaches showed an error pattern that was based on the new eye position and on the depth of the remembered target relative to that position. This suggests that target depth is recomputed after the gaze shift, supporting the retinal model. Our results also confirm earlier literature showing retinal updating of target direction. Furthermore, regression analyses revealed updating gains close to one for both target depth and direction, suggesting that the errors arise after the updating stage during the subsequent reference frame transformations that are involved in reaching.

scholarly journals Effects of cortical damage on binocular depth perception

2016 ◽  
Vol 371 (1697) ◽  
pp. 20150254 ◽  
Author(s):  
Holly Bridge
Keyword(s):  
Depth Perception ◽  
Three Dimensional ◽  
Stereoscopic Vision ◽  
Temporal Lobectomy ◽  
Cortical Atrophy ◽  
Retinal Images ◽  
Posterior Cortical Atrophy ◽  
Retinal Input ◽  
The Brain ◽  
Binocular Depth

Stereoscopic depth perception requires considerable neural computation, including the initial correspondence of the two retinal images, comparison across the local regions of the visual field and integration with other cues to depth. The most common cause for loss of stereoscopic vision is amblyopia, in which one eye has failed to form an adequate input to the visual cortex, usually due to strabismus (deviating eye) or anisometropia. However, the significant cortical processing required to produce the percept of depth means that, even when the retinal input is intact from both eyes, brain damage or dysfunction can interfere with stereoscopic vision. In this review, I examine the evidence for impairment of binocular vision and depth perception that can result from insults to the brain, including both discrete damage, temporal lobectomy and more systemic diseases such as posterior cortical atrophy. This article is part of the themed issue ‘Vision in our three-dimensional world’.

Stereoscopic Depth Perception in Simulated Displays: What Helps and What Hurts?

1996 ◽  
Vol 40 (23) ◽  
pp. 1193-1196 ◽  
Author(s):  
John W. Akers ◽  
Elizabeth T. Davis ◽  
Robert A. King
Keyword(s):  
Depth Perception ◽  
Stereoscopic Depth ◽  
Stimulus Orientation ◽  
Psychophysical Method ◽  
Depth Information ◽  
Stereoscopic Display ◽  
Retinal Disparity ◽  
Vertical Disparity ◽  
Stereoscopic Displays ◽  
Method Of Constant Stimuli

We tested the effect of direction of retinal disparity and stimulus orientation on stereoscopic depth perception to answer three questions. First, are some directions of disparity more efficient than others in providing stereoscopic depth information? Second, does the orientation of an object affect perceived stereoscopic depth? Third, are there any interactions between these parameters? Subjects were tested using a psychophysical, method of constant stimuli procedure with a modified Wheatstone stereoscopic display. Disparity threshold measurements show a significant effect of direction of retinal disparity. Contrary to expectations however, no significant effect of orientation was found if vertical retinal disparities were excluded from the analyses. Stereoacuity thresholds were measurable with obliquely-oriented stimuli and vertical disparity, however, suggesting that vertical disparities can provide useful information. The implications of these results for the graphics, calibration, and design of stereoscopic displays (e.g., HMDs) are discussed.

Nicotine as therapeutic agent in treatment of mood disorders

2016 ◽  
Vol 33 (S1) ◽  
pp. S552-S552
Author(s):  
C. Tsopelas ◽  
N. Petros ◽  
D. Maria ◽  
P. Dimitris ◽  
G.G. Angelica ◽  
...  
Keyword(s):  
Mood Disorders ◽  
Acetylcholine Receptors ◽  
Web Search ◽  
Therapeutic Agent ◽  
Negative Attitude ◽  
Medical Databases ◽  
Positive Effects ◽  
Complex Interactions ◽  
Competing Interest ◽  
The Brain

IntroductionThe plant that has as active ingredient nicotine was chewed or smoked for many years from American natives, for its therapeutic properties. Nowadays after the extensive negative attitude towards smoking, the main provider of nicotine, researchers are now pointing out the therapeutic possibilities of nicotine in mood disorders, as a substance that is acting in the acetylcholine receptors in the brain.AimsIn this review we are trying to explore the possibilities of nicotine use as a therapeutic agent.MethodsWe did a detailed research of the main medical databases, and web search engines for relevant studies. We scrutinize them independently, before reaching consensus about appropriateness for inclusion in the study.ResultsDiadermal administration of nicotine has a positive effect in depressive disorder in 3–8 days, an effect that in one study was reversed after cessation of nicotine. Patients with depression and/or healthy subjects show improvement of attention and working memory after diadermal use of nicotine. Research is not conclusive in the sustainability of these positive affects as other researchers emphasize their short effect in mood.ConclusionNicotine presents as part of novel and promising therapeutic agents with complex interactions with other neurotransmitters in the brain. Before condemning nicotine along with smoking we should acknowledge the potential use of nicotine as a therapeutic compound since research shows that some of these positive effects appear not only to smokers after abstinence but also to non-smokers.Disclosure of interestThe authors have not supplied their declaration of competing interest.

Retinal input influences pace of neurogenesis but not cell-type configuration of the visual forebrain

2021 ◽  
Author(s):  
Shachar Sherman ◽  
Koichi Kawakami ◽  
Herwig Baier
Keyword(s):  
Visual Information ◽  
Visual Stimulation ◽  
Ganglion Cells ◽  
Neuronal Cell ◽  
Cell Types ◽  
Vertebrate Brain ◽  
Relative Contribution ◽  
Retinal Input ◽  
And Migration ◽  
The Brain

The brain is assembled during development by both innate and experience-dependent mechanisms1-7, but the relative contribution of these factors is poorly understood. Axons of retinal ganglion cells (RGCs) connect the eye to the brain, forming a bottleneck for the transmission of visual information to central visual areas. RGCs secrete molecules from their axons that control proliferation, differentiation and migration of downstream components7-9. Spontaneously generated waves of retinal activity, but also intense visual stimulation, can entrain responses of RGCs10 and central neurons11-16. Here we asked how the cellular composition of central targets is altered in a vertebrate brain that is depleted of retinal input throughout development. For this, we first established a molecular catalog17 and gene expression atlas18 of neuronal subpopulations in the retinorecipient areas of larval zebrafish. We then searched for changes in lakritz (atoh7-) mutants, in which RGCs do not form19. Although individual forebrain-expressed genes are dysregulated in lakritz mutants, the complete set of 77 putative neuronal cell types in thalamus, pretectum and tectum are present. While neurogenesis and differentiation trajectories are overall unaltered, a greater proportion of cells remain in an uncommitted progenitor stage in the mutant. Optogenetic stimulation of a pretectal area20,21 evokes a visual behavior in blind mutants indistinguishable from wildtype. Our analysis shows that, in this vertebrate visual system, neurons are produced more slowly, but specified and wired up in a proper configuration in the absence of any retinal signals.

The Brain Stem Saccadic Burst Generator Encodes Gaze in Three-Dimensional Space

2008 ◽  
Vol 99 (5) ◽  
pp. 2602-2616 ◽  
Author(s):  
Marion R. Van Horn ◽  
Pierre A. Sylvestre ◽  
Kathleen E. Cullen
Keyword(s):  
Eye Movements ◽  
Brain Stem ◽  
Dimensional Space ◽  
Three Dimensional ◽  
Saccadic Eye Movements ◽  
Three Dimensions ◽  
Related Information ◽  
Computer Based ◽  
Different Depths ◽  
The Brain

When we look between objects located at different depths the horizontal movement of each eye is different from that of the other, yet temporally synchronized. Traditionally, a vergence-specific neuronal subsystem, independent from other oculomotor subsystems, has been thought to generate all eye movements in depth. However, recent studies have challenged this view by unmasking interactions between vergence and saccadic eye movements during disconjugate saccades. Here, we combined experimental and modeling approaches to address whether the premotor command to generate disconjugate saccades originates exclusively in “vergence centers.” We found that the brain stem burst generator, which is commonly assumed to drive only the conjugate component of eye movements, carries substantial vergence-related information during disconjugate saccades. Notably, facilitated vergence velocities during disconjugate saccades were synchronized with the burst onset of excitatory and inhibitory brain stem saccadic burst neurons (SBNs). Furthermore, the time-varying discharge properties of the majority of SBNs (>70%) preferentially encoded the dynamics of an individual eye during disconjugate saccades. When these experimental results were implemented into a computer-based simulation, to further evaluate the contribution of the saccadic burst generator in generating disconjugate saccades, we found that it carries all the vergence drive that is necessary to shape the activity of the abducens motoneurons to which it projects. Taken together, our results provide evidence that the premotor commands from the brain stem saccadic circuitry, to the target motoneurons, are sufficient to ensure the accurate control shifts of gaze in three dimensions.

Microstimulation of a Neural-Network Model for Visually Guided Saccades

1989 ◽  
Vol 1 (4) ◽  
pp. 317-326 ◽  
Author(s):  
Sabrina J. Goodman ◽  
Richard A. Andersen
Keyword(s):  
Neural Network ◽  
Eye Movements ◽  
Network Model ◽  
Neural Network Model ◽  
Posterior Parietal Cortex ◽  
Single Cells ◽  
Middle Layer ◽  
Retinal Position ◽  
Area 7A ◽  
The Brain

Microstimulation of many saccadic centers in the brain produces eye movements that are not consistent with either a strictly retinal or strictly head-centered coordinate coding of eye movements. Rather, stimulation produces some features of both types of coordinate coding. Recently we demonstrated a neural network model that was trained to localize the position of visual stimuli in head-centered coordinates at the output using inputs of eye and retinal position similar to those converging on area 7a of the posterior parietal cortex of monkeys (Zipser & Andersen 1988; Andersen & Zipser 1988). Here we show that microstimulation of this trained network, achieved by fully activating single units in the middle layer, produces “saccades” that are very much like the saccades produced by stimulating the brain. The activity of the middle-layer units can be considered to code the desired location of the eyes in head-centered coordinates; however, stimulation of these units does not produce the saccades predicted by a classical head-centered coordinate coding because the location in space appears to be coded in a distributed fashion among a population of units rather than explicitly at the level of single cells.

Recasting the Smooth Pursuit Eye Movement System

2004 ◽  
Vol 91 (2) ◽  
pp. 591-603 ◽  
Author(s):  
Richard J. Krauzlis
Keyword(s):  
Eye Movements ◽  
Brain Stem ◽  
Smooth Pursuit ◽  
Visual Motion ◽  
Saccadic Eye Movements ◽  
Extrastriate Cortex ◽  
High Acuity ◽  
Voluntary Eye Movements ◽  
New Perspective ◽  
The Brain

Primates use a combination of smooth pursuit and saccadic eye movements to stabilize the retinal image of selected objects within the high-acuity region near the fovea. Pursuit has traditionally been viewed as a relatively automatic behavior, driven by visual motion signals and mediated by pathways that connect visual areas in the cerebral cortex to motor regions in the cerebellum. However, recent findings indicate that this view needs to be reconsidered. Rather than being controlled primarily by areas in extrastriate cortex specialized for processing visual motion, pursuit involves an extended network of cortical areas, and, of these, the pursuit-related region in the frontal eye fields appears to exert the most direct influence. The traditional pathways through the cerebellum are important, but there are also newly identified routes involving structures previously associated with the control of saccades, including the basal ganglia, the superior colliculus, and nuclei in the brain stem reticular formation. These recent findings suggest that the pursuit system has a functional architecture very similar to that of the saccadic system. This viewpoint provides a new perspective on the processing steps that occur as descending control signals interact with circuits in the brain stem and cerebellum responsible for gating and executing voluntary eye movements. Although the traditional view describes pursuit and saccades as two distinct neural systems, it may be more accurate to consider the two movements as different outcomes from a shared cascade of sensory–motor functions.

scholarly journals Gadolinium Deposition in the Brain: A Systematic Review of Existing Guidelines and Policy Statement Issued by the Canadian Association of Radiologists

2018 ◽  
Vol 69 (4) ◽  
pp. 373-382 ◽  
Author(s):  
Andreu F. Costa ◽  
Christian B. van der Pol ◽  
Pejman Jabehdar Maralani ◽  
Matthew D.F. McInnes ◽  
Jason R. Shewchuk ◽  
...  
Keyword(s):  
Systematic Review ◽  
Working Group ◽  
Conclusive Evidence ◽  
Severe Allergic Reaction ◽  
Policy Statement ◽  
Hepatobiliary Phase ◽  
Phase Imaging ◽  
Gadolinium Deposition ◽  
Canadian Association ◽  
The Brain

Emerging evidence has confirmed that, following administration of a gadolinium-based contrast agent (GBCA), very small amounts of gadolinium will deposit in the brain of humans with intact blood-brain barriers. The literature is evolving rapidly and the degree to which gadolinium will deposit for a particular GBCA or class of GBCAs remains undetermined. Several studies suggest that linear GBCAs deposit more gadolinium in the brain compared with macrocyclic GBCAs; however, our understanding of the molecular composition of deposited gadolinium is preliminary, and the clinical significance of gadolinium deposition remains unknown. To date, there is no conclusive evidence linking gadolinium deposition in the brain with any adverse patient outcome. A panel of radiologists representing the Canadian Association of Radiologists was assembled to assist the Canadian medical imaging community in making informed decisions regarding the issue of gadolinium deposition in the brain. The objectives of the working group were: 1) to review the evidence from animal and human studies; 2) to systematically review existing guidelines and position statements issued by other organizations and health agencies; and 3) to formulate an evidence-based position statement on behalf of the Canadian Association of Radiologists. Based on our appraisal of the evidence and systematic review of 9 guidelines issued by other organizations, the working group established the following consensus statement. GBCA administration should be considered carefully with respect to potential risks and benefits, and only used when required. Standard dosing should be used and repeat administrations should be avoided unless necessary. Gadolinium deposition is one of several issues to consider when prescribing a particular GBCA. Currently there is insufficient evidence to recommend one class of GBCA over another. The panel considered it inappropriate to withhold a linear GBCA if a macrocyclic agent is unavailable, if hepatobiliary phase imaging is required, or if there is a history of severe allergic reaction to a macrocyclic GBCA. Further study in this area is required, and the evidence should be monitored regularly with policy statements updated accordingly.

Sign in / Sign up

Export Citation Format

Share Document