The Precuneus and Visuospatial Attention in Near and far Space: A Transcranial Magnetic Stimulation Study

- We studied the effects of repetitive TMS over right precuneus using a landmark task presented in near and far space.
- Precuneus-TMS produced a rightward shift of this normal bias of perceptual judgments (a “neglect-like” effect).
- This pattern was consistent with the effect of stimulation of the positive control site, the right posterior parietal cortex.
- This provides initial causal evidence related to the spatial attention role of precuneus.
- It supports the presumption of medial and lateral parietal cortex connections.

BackgroundThere is a large body of evidence for the involvement of the parietal cortex in orientation and navigation in space. This has been supplemented by investigation of the contribution of a number of subregions using transcranial magnetic stimulation.ObjectiveThe role of the precuneus area, located in the medial plane of posterior parietal cortex (PPC), in visuospatial functions is not well understood. We investigated the contribution of this area using the landmark task.MethodsParticipants were asked to make forced-choice judgments of which side of prebisected line was longer for near and far viewing conditions (70 and 180 cm, respectively). Online 10 Hz, repetitive transcranial magnetic stimulation (rTMS) was delivered for 500 ms over the right precuneus, rPPC and vertex (control), in separate blocks of trials. The rPPC stimulation was used as a positive control, having previously resulted in “neglect like” spatial bias effects in a number of studies.ResultsA no-TMS condition showed a leftward spatial bias (pseudoneglect) for near space judgments but not for far space and was used as the baseline. Precuneus stimulation resulted in rightward spatial bias from the midpoint in near space similar to the rPPC neglect-like effect. No significant effects were seen with vertex stimulation.ConclusionThis study shows that precuneus, like other parietal areas, is involved in visuospatial functions. Further work is required to clarify how the contribution of this area differs from other parietal regions.