What Happens in Between? Human Oscillatory Brain Activity Related to Crossmodal Spatial Cueing

Maja U Trenner,Manfred Fahle,Hauke R Heekeren,Rüdiger Wenzel,Arno Villringer,Markus Bauer,Konstanze Rössner

doi:10.1371/journal.pone.0001467

Abstract

Previous studies investigated the effects of crossmodal spatial attention by comparing the responses to validly versus invalidly cued target stimuli. Dynamics of cortical rhythms in the time interval between cue and target might contribute to cue effects on performance. Here, we studied the influence of spatial attention on ongoing oscillatory brain activity in the interval between cue and target onset. In a first experiment, subjects underwent periods of tactile stimulation (cue) followed by visual stimulation (target) in a spatial cueing task as well as tactile stimulation as a control. In a second experiment, cue validity was modified to be 50%, 75%, or else 25%, to separate effects of exogenous shifts of attention caused by tactile stimuli from that of endogenous shifts. Tactile stimuli produced: 1) a stronger lateralization of the sensorimotor beta-rhythm rebound (15–22 Hz) after tactile stimuli serving as cues versus not serving as cues; 2) a suppression of the occipital alpha-rhythm (7–13 Hz) appearing only in the cueing task (this suppression was stronger contralateral to the endogenously attended side and was predictive of behavioral success); 3) an increase of prefrontal gamma-activity (25–35 Hz) specifically in the cueing task. We measured cue-related modulations of cortical rhythms which may accompany crossmodal spatial attention, expectation or decision, and therefore contribute to cue validity effects. The clearly lateralized alpha suppression after tactile cues in our data indicates its dependence on endogenous rather than exogenous shifts of visuo-spatial attention following a cue independent of its modality.

Highlights

Spatial cueing tasks have been widely used to investigate shifts of spatial attention [1,2]
Exogenous attention tended to dominate at earlier stages of visual processing in the brain while endogenous attention tended to dominate at later stages
Please note that in this study we focus on the period between the cue and the target stimulus (ISI), which is not influenced by the overt response to the targets

Summary

Introduction

Spatial cueing tasks have been widely used to investigate shifts of spatial attention [1,2]. The side initially advantaged by an exogenously induced attention shift is disadvantaged at stimulus-onset-asynchronies (SOAs) of more than about 400 ms, the so-called ‘inhibition of return’, IOR [11,12,13,14] This phenomenon has been interpreted as an effect of either the reorientation of attention or of saccade preparation and inhibition [11,15,16,17]. Mayer et al (2004) used optimized stimulation designs for exogenous and endogenous spatial cueing, respectively, for example shorter SOAs for exogenous cueing [12] They found a distinct network activated by voluntary attention shifts including the bilateral temporoparietal junction, bilateral superior temporal gyrus, right middle temporal gyrus, right frontal eye field, and left intraparietal sulcus. The influences of both types of attention interfered with each other thereby providing evidence for partially separate but interacting attention systems

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