Plantar stimulation can affect subjective straight-ahead in neglect patients

The rightward orientation bias of neglect patients has been shown to be dec reased by postural changes, suggesting that afferences coding the posture r elative to gravity might influence the body-centred spatial reference frame . In order to test this hypothesis, we evaluated the effects of plantar sti mulations on the subjective straight-ahead (SSA) of two neglect patients pr esenting with a strong rightward sh ift, as well as two non-neglect patient s and three normal subjects. Vibratory or electrical stimulations were appl ied to the left or right plantar sole. Data showed that these manipulations influenced the SSA position in neglect patients only. The observed improve ment could be explained by a direction-specific effect of vibration, in add ition to a non-specific activation induced by both stimulations. (C) 2001 E lsevier Science Ireland Ltd. All rights reserved.