Macula and periphery: Their contributions to the visual evoked potentials (VEP) in humans

Abstract

An alternating checkerboard pattern subtending a visual angle of 25 min arc is capable of eliciting remarkably high amplitudes of visually evoked potentials (VEP) outside a visual angle of 2.5 degree. These contributions cannot be neglected when evaluating a VEP response obtained with a larger field of stimulation. When the retina is consecutively stimulated by concentric frame-shaped stimuli, the algebraic sum of all single cortical responses augmented the cortical response obtained when stimulating the whole field simultaneously by approximately 30%. This finding may be explained by the inhibiting interactions within the receptive field organisation of the retina.

Unusual Visual Evoked Potentials in Patients with Age-Related Macular Degeneration

“…The late perifoveal components were also reported by Fukui et al [20]. From our data and from data of Campbell and Maffei [24]and of Röver and co-workers [1], it is unlikely that the macular response is just the arithmetic sum of the foveal and perifoveal responses. However, for contrast sensitivity functions measured with the steady-state VEP, Cannon [25]showed pure additivity of foveal and perifoveal components.…”

“…The increase in prVEP amplitudes with increasing size of the stimulus field is well documented in normal controls and may reflect the increasing number of activated receptive fields contributing to the response [1, 2, 3, 4]. It is also known that cortical responses elicited by stimulation of the central retina are reduced and prolonged in patients with macular diseases and subjects with experimental central scotoma [14, 19, 20].…”

“…The amplitude of the prVEP in normals usually increases with increasing field size [1, 2, 3, 4]. However, it is also known that its amplitude decreases with increasing eccentricity of the stimulated retinal area [5, 6].…”

Amplitudes of Visually Evoked Cortical Responses due to Full-Field Stimulation and to Stimulation with Four Half-Fields

“…The sums of lower plus upper half field amplitude as well as nasal plus temporal half-field amplitude are both significantly larger than the full-field amplitude. Groneberg [1980], Rover et al [1980] and Stohr et al [1982] obtained the same results. An explanation can be the inconstant fixation and normal eye saccades so that the retinal area on both sides of the line of contact between two half-fields is stimulated twofold [Rover et al, 1980].…”

“…Groneberg [1980], Rover et al [1980] and Stohr et al [1982] obtained the same results. An explanation can be the inconstant fixation and normal eye saccades so that the retinal area on both sides of the line of contact between two half-fields is stimulated twofold [Rover et al, 1980]. That means the overall area stimulated by two half fields is greater than the area stimulated by a full field.…”