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Advancing a Model to Account for Abnormal Spatial Relationship Perception in Bulbar Cyclotorsion.

Aleci C - Cureus (2015)

Bottom Line: In both cases, we advanced bulbar torsion to be responsible for the reduced sensibility to spatial relationship along the x-coordinate.Still, a possible explanation and a tentative model accounting for the results at that time had not been provided.Such a model of the "dual horizon" seems to be able to account for the experimental finding described in the previous paper, providing a theoretical explanation for the defective sense of space in patients suffering from cyclotropia.

View Article: PubMed Central - HTML - PubMed

Affiliation: Dept of Ophthalmology, The Gradenigo Hospital ; Neuro-Ophthalmology center, University of Turin.

ABSTRACT
In a previous study dated back to 2001, a small sample of cyclotropic patients were found to be affected by abnormal spatial relationship perception (aspect ratio judgment) with increased discrimination threshold of elliptical targets oriented along the horizontal axis. The angular amount of incyclodeviation correlated significantly with the discrimination threshold along the horizontal axis. Our group made a similar finding some years later in subjects suffering from Menière's syndrome. In both cases, we advanced bulbar torsion to be responsible for the reduced sensibility to spatial relationship along the x-coordinate. Still, a possible explanation and a tentative model accounting for the results at that time had not been provided. This paper aims at making up for the gap, advancing a paradigm that explains the increased discrimination threshold in cyclotropic eyes as a function of the angular discrepancy between the horizontal coordinate on the retinal plane, corresponding to the maculopapillary axis (the "retinal horizon"), and the horizontal coordinate in the visual space (the "spatial horizon"). This angular discrepancy is posited to produce abnormal encoding of the spatial relationship of the target, leading to an unbalanced activation of the two antagonistic cellular pools responsible for the analysis of the aspect ratio at the cortical level. Such a model of the "dual horizon" seems to be able to account for the experimental finding described in the previous paper, providing a theoretical explanation for the defective sense of space in patients suffering from cyclotropia.

No MeSH data available.


Related in: MedlinePlus

SR encoding value of the retinal detectors depends on their position relative to the retinal horizon (II). The SR encoding value of the retinal detectors depends on their position relative to the retinal horizon. In case of bulbar intorsion, the SR value increases by an amount Vl, proportional of the angular difference between retinal and spatial horizon. The additional effect of Vl would lead to over-activation of the V-cortical pool, thereby to overestimation of the aspect ratio along the y-axis (increased SR threshold along the horizontal axis). Red: SR value; Black: Vl. Numbers are reported only for illustrative purpose.
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FIG3: SR encoding value of the retinal detectors depends on their position relative to the retinal horizon (II). The SR encoding value of the retinal detectors depends on their position relative to the retinal horizon. In case of bulbar intorsion, the SR value increases by an amount Vl, proportional of the angular difference between retinal and spatial horizon. The additional effect of Vl would lead to over-activation of the V-cortical pool, thereby to overestimation of the aspect ratio along the y-axis (increased SR threshold along the horizontal axis). Red: SR value; Black: Vl. Numbers are reported only for illustrative purpose.

Mentions: If a bulbar torsion λ occurs, φr and φs differ by a value Vλ. In this case, the retinal detectors activated by the boundary of the proximal stimulus are shifted vertically relative to the spatial horizon by Vλ. In their new position φr’, their actual response would be dictated by their proper SR-coding value depending on φr , plus an additional amount proportional to Vλ. For nasal tilting (incyclotorsion), such a higher SR-coding value makes the encoding of the aspect ratio along the vertical preponderant, causing hyperactivation of the V-cellular cortical pool. The subjective visual outcome would be unbalanced spatial relationship perception along the vertical axis proportional to φr+Vλ, leading to increased SR discrimination threshold along the horizontal coordinate (Figure 3).


Advancing a Model to Account for Abnormal Spatial Relationship Perception in Bulbar Cyclotorsion.

Aleci C - Cureus (2015)

SR encoding value of the retinal detectors depends on their position relative to the retinal horizon (II). The SR encoding value of the retinal detectors depends on their position relative to the retinal horizon. In case of bulbar intorsion, the SR value increases by an amount Vl, proportional of the angular difference between retinal and spatial horizon. The additional effect of Vl would lead to over-activation of the V-cortical pool, thereby to overestimation of the aspect ratio along the y-axis (increased SR threshold along the horizontal axis). Red: SR value; Black: Vl. Numbers are reported only for illustrative purpose.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4494463&req=5

FIG3: SR encoding value of the retinal detectors depends on their position relative to the retinal horizon (II). The SR encoding value of the retinal detectors depends on their position relative to the retinal horizon. In case of bulbar intorsion, the SR value increases by an amount Vl, proportional of the angular difference between retinal and spatial horizon. The additional effect of Vl would lead to over-activation of the V-cortical pool, thereby to overestimation of the aspect ratio along the y-axis (increased SR threshold along the horizontal axis). Red: SR value; Black: Vl. Numbers are reported only for illustrative purpose.
Mentions: If a bulbar torsion λ occurs, φr and φs differ by a value Vλ. In this case, the retinal detectors activated by the boundary of the proximal stimulus are shifted vertically relative to the spatial horizon by Vλ. In their new position φr’, their actual response would be dictated by their proper SR-coding value depending on φr , plus an additional amount proportional to Vλ. For nasal tilting (incyclotorsion), such a higher SR-coding value makes the encoding of the aspect ratio along the vertical preponderant, causing hyperactivation of the V-cellular cortical pool. The subjective visual outcome would be unbalanced spatial relationship perception along the vertical axis proportional to φr+Vλ, leading to increased SR discrimination threshold along the horizontal coordinate (Figure 3).

Bottom Line: In both cases, we advanced bulbar torsion to be responsible for the reduced sensibility to spatial relationship along the x-coordinate.Still, a possible explanation and a tentative model accounting for the results at that time had not been provided.Such a model of the "dual horizon" seems to be able to account for the experimental finding described in the previous paper, providing a theoretical explanation for the defective sense of space in patients suffering from cyclotropia.

View Article: PubMed Central - HTML - PubMed

Affiliation: Dept of Ophthalmology, The Gradenigo Hospital ; Neuro-Ophthalmology center, University of Turin.

ABSTRACT
In a previous study dated back to 2001, a small sample of cyclotropic patients were found to be affected by abnormal spatial relationship perception (aspect ratio judgment) with increased discrimination threshold of elliptical targets oriented along the horizontal axis. The angular amount of incyclodeviation correlated significantly with the discrimination threshold along the horizontal axis. Our group made a similar finding some years later in subjects suffering from Menière's syndrome. In both cases, we advanced bulbar torsion to be responsible for the reduced sensibility to spatial relationship along the x-coordinate. Still, a possible explanation and a tentative model accounting for the results at that time had not been provided. This paper aims at making up for the gap, advancing a paradigm that explains the increased discrimination threshold in cyclotropic eyes as a function of the angular discrepancy between the horizontal coordinate on the retinal plane, corresponding to the maculopapillary axis (the "retinal horizon"), and the horizontal coordinate in the visual space (the "spatial horizon"). This angular discrepancy is posited to produce abnormal encoding of the spatial relationship of the target, leading to an unbalanced activation of the two antagonistic cellular pools responsible for the analysis of the aspect ratio at the cortical level. Such a model of the "dual horizon" seems to be able to account for the experimental finding described in the previous paper, providing a theoretical explanation for the defective sense of space in patients suffering from cyclotropia.

No MeSH data available.


Related in: MedlinePlus