Do neck-proprioceptive and caloric-vestibular stimulation influence covert visual attention in normals, as they influence visual neglect?

Neck-proprioceptive and caloric-vestibular stimulation have been shown to ameliorate the spatial bias exhibited by patients suffering from unilateral visual neglect. These interventions might in principle have their effect by biasing covert attention towards the neglected side. If so, the same interventions should also modulate covert attention in neurologically-intact subjects. However, we demonstrate here that neither neck-proprioception (vibration of left neck muscles) nor caloric-vestibular stimulation (injection of iced water into the left ear) affect covert visual attention in healthy individuals. These results from normals may distinguish between different accounts for unilateral neglect in patients. In particular, they argue against explanations of neglect solely in terms of a pathological misperception of body orientation within an otherwise normal neural representation of space.