Involuntary orienting of attention to a sound desynchronizes the occipital alpha rhythm and improves visual perception.

Directing attention voluntarily to the location of a visual target results in an amplitude reduction (desynchronization) of the occipital alpha rhythm (8-14Hz), which is predictive of improved perceptual processing of the target. Here we investigated whether modulations of the occipital alpha rhythm triggered by the involuntary orienting of attention to a salient but spatially non-predictive sound would similarly influence perception of a subsequent visual target. Target discrimination was more accurate when a sound preceded the target at the same location (validly cued trials) than when the sound was on the side opposite to the target (invalidly cued trials). This behavioral effect was accompanied by a sound-induced desynchronization of the alpha rhythm over the lateral occipital scalp. The magnitude of alpha desynchronization over the hemisphere contralateral to the sound predicted correct discriminations of validly cued targets but not of invalidly cued targets. These results support the conclusion that cue-induced alpha desynchronization over the occipital cortex is a manifestation of a general priming mechanism that improves visual processing and that this mechanism can be activated either by the voluntary or involuntary orienting of attention. Further, the observed pattern of alpha modulations preceding correct and incorrect discriminations of valid and invalid targets suggests that involuntary orienting to the non-predictive sound has a rapid and purely facilitatory influence on processing targets on the cued side, with no inhibitory influence on targets on the opposite side.

Spatial remapping of tactile events: Assessing the effects of frequent posture changes.

During the apparently mindless act of localizing a tactile sensation, our brain must realign its initial spatial representation (somatotopicaly arranged) according to current body posture (arising from proprioception, vision and even audition).1-3 We have recently illustrated4 the temporal course of this recoding of tactile space from somatotopic to external coordinates using a crossmodal cueing psychophysical paradigm5,6 where behavioral reactions to visual targets are evaluated as a function of the location of irrelevant tactile cues. We found that the tactile events are initially represented in terms of a fleeting, non-conscious but nevertheless behaviorally consequential somatotopic format, which is quickly replaced by the representations referred to external spatial locations that prevail in our everyday experience. In this addendum, we test the intuition that frequent changes in body posture will make it harder to update the spatial remapping system and thus, produce stronger psychophysical correlates of the initial somatotopically-based spatial representations. Contrary to this expectation, however, we found no evidence for a modulation when preventing adaptation to a body posture.