Covert attention modulates the SSVEP in a paradigm suitable for infants and young children.

Abstract

Attention and visual gaze are usually tightly linked. Sometimes, however, we attend covertly to peripheral events without redirecting our gaze from the event that first attracted our overt attention. Despite evidence in adults that the steady-state visual evoked potential (SSVEP) varies with modulation of covert attention, paradigms used with adults are not suitable for use with infants and young children who cannot be instructed to perform tasks that dissociate overt from covert attention. Here, we provide evidence from a paradigm suitable for infants and young children that when gaze remains fixed on a central flickering visual stimulus while covert attention is directed briefly to the peripheral visual field, the SSVEP response undergoes significant attenuation. Signal-to-noise ratio (SNR) and intertrial coherence (ITC) measures of the SSVEP response to the central stimulus were lower when participants covertly deployed their attention to the peripheral stimulus than when central gaze and attention were aligned. Crucially, SNR was a more robust measure of attentional modulation than ITC, even though both measures were significantly correlated. Moreover, a 6 Hz flicker of the central stimulus resulted in a more reliable measure of attentional modulation than 12 Hz, and the inclusion of higher harmonics did not improve the reliability of either the SNR or the ITC measures. Our paradigm is unique in that it relies on short (2 s) response epochs, validates eye position during rapid shifts of covert attention, and makes it possible to obtain SSVEP measures of covert attention from infants, young children, and special populations.