Reduced evoked activity and cortical oscillations are correlated with anisometric amblyopia and impairment of visual acuity

Hanna Julku,J Matias Palva,Jyrki P Mäkelä,Satu Palva,Elina Karvonen,Henri J Huttunen,Johanna Liinamaa,Laura Lindberg,Eero Castrén,Hannu Uusitalo,Santeri Rouhinen,Ville Saarela,Sigrid Booms

doi:10.1038/s41598-021-87545-9

Abstract

Amblyopia is a developmental disorder associated with abnormal visual experience during early childhood commonly arising from strabismus and/or anisometropia and leading to dysfunctions in visual cortex and to various visual deficits. The different forms of neuronal activity that are attenuated in amblyopia have been only partially characterized. In electrophysiological recordings of healthy human brain, the presentation of visual stimuli is associated with event-related activity and oscillatory responses. It has remained poorly understood whether these forms of activity are reduced in amblyopia and whether possible dysfunctions would arise from lower- or higher-order visual areas. We recorded neuronal activity with magnetoencephalography (MEG) from anisometropic amblyopic patients and control participants during two visual tasks presented separately for each eye and estimated neuronal activity from source-reconstructed MEG data. We investigated whether event-related and oscillatory responses would be reduced for amblyopia and localized their cortical sources. Oscillation amplitudes and evoked responses were reduced for stimuli presented to the amblyopic eye in higher-order visual areas and in parietal and prefrontal cortices. Importantly, the reduction of oscillation amplitudes but not that of evoked responses was correlated with decreased visual acuity in amblyopia. These results show that attenuated oscillatory responses are correlated with visual deficits in anisometric amblyopia.

Highlights

Amblyopia is a developmental disorder associated with abnormal visual experience during early childhood commonly arising from strabismus and/or anisometropia and leading to dysfunctions in visual cortex and to various visual deficits
We tested whether the reduction of visual acuity between fellow eye (FE) and amblyopic eye (AE) were correlated with neuronal activity as measured with Event-related responses (ERs) and oscillation amplitudes
Abnormal oscillations and synchronization are thought to contribute to symptoms and emergence of many neurodevelopmental brain d iseases[23,41,42,52], oscillations being attenuated in hemianopia[40] and in animal models of strabismic amblyopia[45]

Summary

Introduction

Amblyopia is a developmental disorder associated with abnormal visual experience during early childhood commonly arising from strabismus and/or anisometropia and leading to dysfunctions in visual cortex and to various visual deficits. In electrophysiological recordings of healthy human brain, the presentation of visual stimuli is associated with event-related activity and oscillatory responses It has remained poorly understood whether these forms of activity are reduced in amblyopia and whether possible dysfunctions would arise from lower- or higher-order visual areas. Amblyopia is characterized by abnormal visual-performance-related functions localized to primary visual cortex, i.e., to the visual acuity measures and measures related to contrast sensitivity, which are pronounced for stimuli with high spatial frequencies[3,4,5,6,7]. Because no studies have neither identified the cortical sources underlying these reduced responses nor addressed whether they are correlated with the visual acuity deficit and severity of amblyopia, the functional significance of this suppression has remained unresolved

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