Preparatory α-band oscillations reflect spatial gating independently of predictions regarding target identity.
Wildegger T., van Ede F., Woolrich M., Gillebert CR., Nobre AC.
Preparatory modulations of cortical α-band oscillations are a reliable index of the voluntary allocation of covert spatial attention. It is currently unclear whether attentional cues containing information about a target's identity (such as its visual orientation), in addition to its location, might additionally shape preparatory α modulations. Here, we explore this question by directly comparing spatial and feature-based attention in the same visual detection task while recording brain activity using magnetoencephalography (MEG). At the behavioral level, preparatory feature-based and spatial attention cues both improved performance and did so independently of each other. Using MEG, we replicated robust α lateralization following spatial cues: in preparation for a visual target, α power decreased contralaterally and increased ipsilaterally to the attended location. Critically, however, preparatory α lateralization was not significantly modulated by predictions regarding target identity, as carried via the behaviorally effective feature-based attention cues. Furthermore, nonlateralized α power during the cue-target interval did not differentiate between uninformative cues and cues carrying feature-based predictions either. Based on these results we propose that preparatory α modulations play a role in the gating of information between spatially segregated cortical regions and are therefore particularly well suited for spatial gating of information.NEW & NOTEWORTHYThe present work clarifies if and how human brain oscillations in the α-band support multiple types of anticipatory attention. Using magnetoencephalography, we show that posterior α-band oscillations are modulated by predictions regarding the spatial location of an upcoming visual target, but not by feature-based predictions regarding its identity, despite robust behavioral benefits. This provides novel insights into the functional role of preparatory α mechanisms and suggests a limited specificity with which they may operate.