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

TL;DR

This paper proposes a new model explaining how abnormal eye rotation affects spatial perception in patients with cyclotropia.

Contribution

The paper introduces a theoretical model called the 'dual horizon' to explain spatial perception deficits in cyclotropia.

Findings

Abnormal spatial perception in cyclotropia is linked to angular discrepancies between retinal and spatial horizons.

The proposed model explains increased discrimination thresholds in cyclotropic eyes.

The model suggests unbalanced cortical activation due to abnormal spatial encoding.

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.

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