Abstract
IntroductionThe relationship between stimulus property, brain activity, and the VEP is still a matter of uncertainty.MethodWe recorded the VEP of 43 volunteers when viewing a series of dartboard images presented as both a pattern reversing and pattern onset/offset stimulus. Across the dartboard images, the total stimulus area undergoing a luminance contrast change was varied in a graded manner.ResultsWe confirmed the presence of two independent neural processing stages. The amplitude of VEP components across our pattern reversing stimuli signaled a phasic neural response based on a temporal luminance contrast selective mechanism. The amplitude of VEP components across the pattern onset stimuli signaled both a phasic and a tonic neural response based on a temporal‐ and spatial luminance contrast selective mechanism respectively. Oscillation frequencies in the VEP suggested modulation of the phasic neural response by feedback from areas of the dorsal stream, while feedback from areas of the ventral stream modulated the tonic neural response. Each processing stage generated a sink and source phase in the VEP. Source localization indicated that during the sink phase electric current density was highest in V1, while during the source phase electric current density was highest in extra‐striate cortex. Our model successfully predicted the appearance of the VEP to our images whether presented as a pattern reversing or a pattern onset/offset stimulus.ConclusionsFocussing on the effects of a phasic and tonic response rather than contrast response function on the VEP, enabled us to develop a theory linking stimulus property, neural activity and the VEP.
Highlights
The relationship between stimulus property, brain activity, and the visual evoked potential (VEP) is still a matter of uncertainty
The findings of our study led us to the conclusion that the difference in the appearance of the VEP to a pattern reversing and pattern onset stimulus does not arise from a difference in neural response
Instead it arises from the ability of the neural response driven by the magno- and parvocellular system to manifest itself in the VEP
Summary
During the past three decades, magnetic resonance imaging has been used to map the anatomy of the neural macro-networks serving perception and cognition and to trace their interconnections. The VEP obtained when viewing a chequerboard as a pattern reversing stimulus differs markedly from the VEP obtained when viewing the identical chequerboard as a pattern onset stimulus As perplexing as this observation may be, it can provide insights into the relationship between stimulus property, neural activity and the VEP. The dartboard images were generated such that the total stimulus area undergoing a luminance contrast change was varies in a graded manner This altered the size of the neural population activated during the neural luminance component. Appraising the contrast information in a dartboard image enabled us to compare the amplitude of VEP components to the size of the neural population coding its pattern This revealed parallels between properties of the VEP and characteristics of the magno-and parvocellular system
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