Evaluation of Visual Parameters by Visual Evoked Potentials Captured by EEG

Université Catholique de Louvain100 enrolled

Overview

This project will be based on an approach that has already proven itself in the field of the development of low-level visual functions such as visual acuity, vernier acuity and contrast sensitivity (Norcia \& Tyler, 1985): scanning visual evoked potentials" (sVEP), a special case of steady-state visual evoked potentials (SSVEP). While SSVEPs consist of presenting a visual stimulus periodically, sVEPs are SSVEPs where the value of a parameter (e.g. the contrast of the stimulus) varies. This variation ("scanning") makes it possible to determine the threshold value where an electroencephalographic (EEG) response is perceived, and thus to evaluate visual parameters such as visual acuity, vernier acuity and contrast sensitivity. In this study we therefore record the amplitude of the EEG electrical signal during the presentation of low-level stimuli such as spatial frequency gratings or increasing or decreasing contrast.

Study Type

OBSERVATIONAL

Enrollment

100

Conditions

Visual Neurosciences

Interventions

68-electrode electroencephalography with steady state visual evoked potentialsOTHER

Electroencephalography is registered through a 68-electrode electroencephalography while stimuli will be presented at the centre of the screen at a distance of 150cm. The pattern of visual stimulation is based on the technique of steady state visual evoked potentials. These potentials consist of the presentation of a visual stimulus at a (relatively fast) periodic rate to produce an EEG signal over the occipital cortex exactly at the frequency of stimulation. By varying the value of a parameter of the stimulation (e.g. the contrast of the stimulus) varies. This variation makes it possible to determine the threshold value where an EEG response is perceived, and thus to evaluate visual parameters such as visual acuity, contrast sensitivity or recognition of more complex shapes.

Eligibility

Sex: ALLMin age: 1 YearMax age: 75 YearsHealthy volunteers:

Medical Language ↔ Plain English

Inclusion Criteria: * Absence of ocular pathologies except for refractive errors * Absence of neurologic conditions Exclusion Criteria: * Participants using neurologic or psychiatric drugs * Scalp pathology

Outcomes

Primary Outcomes

Threshold of visual recognition of low and high grade visual stimuli

Fast periodic visual stimulation using stimuli such as gratings, checkerboards, words and faces

Time frame: 4 months