Alpha oscillations reflect similar mapping mechanisms for localizing touch on hands and tools

Abstract

Numerous studies have suggested that tools become incorporated into a representation of our body. A prominent hypothesis suggests that our brain re-uses body-based computations when we use tools. However, little is known about how this is implemented at the neural level. Here we used the ability to localize touch on both tools and body parts as a case study to fill this gap. Neural oscillations in the alpha (8-13 Hz) and beta (15-25 Hz) frequency bands are involved in mapping touch on the body in distinct reference frames. Alpha activity reflects the mapping of touch in external coordinates, whereas beta activity reflects the mapping of touch in skin-centered coordinates. Here, we aimed at pinpointing the role of these oscillations during tool-extended sensing. We recorded participants' oscillatory activity while tactile stimuli were applied to either hands or the tips of hand-held rods. The posture of the hands/tool-tips was uncrossed or crossed at participants' body midline in order for us to disentangle brain responses related to different coordinate systems. We found that alpha-band activity was modulated similarly across postures when localizing touch on hands and on tools, reflecting the position of touch in external space. Source reconstruction also indicated a similar network of cortical regions involved for tools and hands. Our findings strongly suggest that the brain uses similar oscillatory mechanisms for mapping touch on the body and tools, supporting the idea of neural processes being repurposed for tool-use.

Tool use fine-tunes arm and tool maps

“…Our plots (Figure 3A) and post-hoc tests show that the resolution of the spatial maps increased for central locations on the arm and for the distal boundary of the tool (i.e., tool tip). The close link between localization precision and somatosensory spatial computations (e.g., trilateration) (Miller et al, 2022;Fabio et al, 2024), suggests that tool use modified the computations that build the spatial maps of the arm and tool. We speculate that increased precision at the tool tip may reflect a more prominent role for the tip when computing location within the Peviani et al, Tool use fine-tunes arm and tool maps ______________________________________________________________________________ 10 arm+tool system, following the extensive sensorimotor feedback gathered during the interaction with the tool.…”