PUB - Publikationen an der Universität Bielefeld

Oscillatory alpha-band activity is commonly associated with spatial attention and multisensory prioritization. It has also been suggested to reflect the automatic transformation of tactile stimuli from a skin-based, somatotopic reference frame into an external one. Previous research has not convincingly separated these two possible roles of alpha-band activity. Previous experimental paradigms have used artificially long delays between tactile stimuli and behavioral responses to aid relating oscillatory activity to these different events. However, this strategy potentially blurs the temporal relationship of alpha-band activity relative to behavioral indicators of tactile-spatial transformations. Here, we assessed alpha-band modulation with massive univariate deconvolution, an analysis approach that disentangles brain signals overlapping in time and space. Thirty-one male and female human participants performed a delay-free, visual search task in which saccade behavior was unrestricted. A tactile cue to uncrossed or crossed hands was either informative or uninformative about visual target location. Alpha-band suppression following tactile stimulation was lateralized relative to the stimulated hand over centro-parietal electrodes, but relative to its external location over parieto-occipital electrodes. Alpha-band suppression reflected external touch location only after informative cues, suggesting that posterior alpha-band lateralization does not index automatic tactile transformation. Moreover, alpha-band suppression occurred at the time of, or after, the production of the saccades guided by tactile stimulation. These findings challenge the idea that alpha-band activity is directly involved in tactile-spatial transformation and suggest instead that it reflects delayed, supramodal processes related to attentional reorienting.SIGNIFICANCE STATEMENTLocalizing a touch in space requires integrating somatosensory information about skin location and proprioceptive or visual information about posture. The automatic remapping between skin-based tactile information to a location in external space has been proposed to rely on the modulation of oscillatory brain activity in the alpha-band range, across the multiple cortical areas that are involved in tactile, multisensory, and spatial processing. We report two findings that are inconsistent with this view. First, alpha-band activity reflected the remapped stimulus location only when touch was task-relevant. Second, alpha-band modulation occurred too late to account for spatially directed behavioral responses and, thus, only after remapping must have taken place. These characteristics contradict the idea that alpha-band directly reflects automatic tactile remapping processes. Copyright © 2020 the authors.