This might suggest that manipulations of voluntary attention do little to speed the process of remapping somatosensory stimuli from anatomical to external spatial coordinates. This possibility is certainly consistent with accounts of somatosensory processing which have characterized the early anatomically based stages of processing as automatic and unconscious (Kitazawa, 2002; Azañón & Soto-Faraco, 2008). In the
study reported here we compared somatosensory processing under conditions in which information about arm posture was provided either by both visual and proprioceptive cues in combination (Exp. 1) or by proprioceptive cues only (Exp. 2). Despite one morphological difference of note – that the P100 and N140 MK-1775 solubility dmso components, which were clearly dissociable in Experiment 1, could not be separately distinguished in Experiment 2 – the SEPs which we observed were largely similar between the two conditions. The effects of posture were observed within 25 ms of one another across the two experiments (Exp. 1 – 128 ms, Exp. 2 – 150 ms). The fact that postural effects can be observed under both of these conditions is consistent with the Daporinad manufacturer finding that neurons in primate premotor cortex will remap multisensory correspondences
between touch and vision on the basis of both visual and proprioceptive
cues to posture together and in isolation (e.g. Graziano, 1999). However, the hemispheric distribution of the modulation of the SEPs by posture varied between experiments. Silibinin When participants had sight of their hands as well as signals from proprioception (Exp. 1), an enhancement of the amplitude of the N140 when the hands were across the midline was observed over the contralateral but not the ipsilateral hemisphere. This effect reversed when the participants’ limbs were covered (Exp. 2), with crossed-hands leading to an enhanced N140 recorded over the ipsilateral sites. Because of the differences between the time-windows which we used to compare the N140 across experiments (see above), we examined the Posture × Hemisphere × Experiment interaction with a sample-point by sample-point analysis using a Monte Carlo simulation method (based on Guthrie & Buchwald, 1991). This confirmed that hemispheric variation in posture effects according to the availability of vision of the hand occurred around the N140 component (from 152 ms). This hemispheric variation in posture effects coincides with some prior findings from an fMRI study by Lloyd et al. (2003). Lloyd et al.