Balaban et al. (J. Neurophys. 88 (2002) 3175-3193) described a population of brainstem neurons responsive to natural vestibular stimulation, located in the parabrachial nucleus (PBN) of alert macaque monkeys. Prior work (McCandless and Balaban, SfN 2004) demonstrated that these units respond to periodic rotational stimuli in horizontal and vertical planes, and to OVAR. Here, we report that neurons of the parabrachial nucleus responsive to linear acceleration (i.e. tilt) stimuli exhibit different spatial tuning during vertical plane tilts versus OVAR, and during bidirectional OVAR. During vertical plane tilts, the distribution of spatial tuning responses was unremarkable. However, during OVAR, the orientation of peak spatial tuning responses tended to shift toward the directions of vertical canal planes. Neurons in the left parabrachial nucleus appear to shift their peak response direction toward the left-anterior / right posterior canal plane during clockwise rotation, and toward the right anterior / left ...