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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 (III).Same as Figure 3 but for bulbar excyclotorsion. Upper panels: no torsion; lower panel: extorsion. See text for explanation.
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FIG4: SR encoding value of the retinal detectors depends on their position relative to the retinal horizon (III).Same as Figure 3 but for bulbar excyclotorsion. Upper panels: no torsion; lower panel: extorsion. See text for explanation.

Mentions: In case of excyclotorsion, the temporal tilting causes downward shift of the retinal horizon in the temporal (rather than nasal) hemiretina and upward shift of the retinal horizon in the nasal (rather than temporal) hemiretina. The reverse tilting of the retinal horizon reduces the SR-value of the retinal detectors shifted by the bulbar torsion by a value Vλ. This reduction makes the encoding of the aspect ratio along the horizontal preponderant, causing hypoactivation of the V-cellular cortical pool (or, alternatively, hyperactivation of the H-pool). The subjective visual outcome would be unbalanced spatial relationship perception along the horizontal axis proportional to φr-Vλ; therefore, reduced SR discrimination threshold along the horizontal coordinate (conversely, increased threshold along the vertical axis is expected - see Figure 4).


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 (III).Same as Figure 3 but for bulbar excyclotorsion. Upper panels: no torsion; lower panel: extorsion. See text for explanation.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

FIG4: SR encoding value of the retinal detectors depends on their position relative to the retinal horizon (III).Same as Figure 3 but for bulbar excyclotorsion. Upper panels: no torsion; lower panel: extorsion. See text for explanation.
Mentions: In case of excyclotorsion, the temporal tilting causes downward shift of the retinal horizon in the temporal (rather than nasal) hemiretina and upward shift of the retinal horizon in the nasal (rather than temporal) hemiretina. The reverse tilting of the retinal horizon reduces the SR-value of the retinal detectors shifted by the bulbar torsion by a value Vλ. This reduction makes the encoding of the aspect ratio along the horizontal preponderant, causing hypoactivation of the V-cellular cortical pool (or, alternatively, hyperactivation of the H-pool). The subjective visual outcome would be unbalanced spatial relationship perception along the horizontal axis proportional to φr-Vλ; therefore, reduced SR discrimination threshold along the horizontal coordinate (conversely, increased threshold along the vertical axis is expected - see Figure 4).

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