Neuropsychologia xxx (2006) xxx–xxx Asymmetrical perception of body rotation after unilateral injury to human vestibular cortex John W. Philbeck a,∗ , Marlene Behrmann b , Tim Biega c , Lucien Levy c a Department of Psychology, George Washington University, 2125 G. Street, NW, Washington, DC 20052, USA b Carnegie Mellon University, Department of Psychology, Pittsburgh, PA, USA c George Washington University Medical Center, Department of Radiology, Washington, DC, USA Received 8 June 2005; received in revised form 3 February 2006; accepted 15 February 2006 Abstract Vestibular information plays a key role in many perceptual and cognitive functions, but surprisingly little is known about how vestibular signals are processed at the cortical level in humans. To address this issue, we tested the ability of two patients, with damage to key components of the vestibular network in either the left or right hemisphere, to perceive passive whole-body rotations (25–125 ◦ ) about the yaw axis. In both patients, the posterior insula, hippocampus, putamen, and thalamus were extensively damaged. The patients’ responses were compared with those of nine age- and sex-matched neurologically intact participants. The body rotations were conducted without vision and the peak angular velocities ranged from 40 ◦ to 90 ◦ per second. Perceived rotation was assessed by open-loop manual pointing. The right hemisphere patient exhibited poor sensitivity for body rotations toward the contralesional (left) hemispace and generally underestimated the rotations. By contrast, his judgments of rotations toward the ipsilesional (right) hemispace greatly overestimated the physical rotation by 50–70 ◦ for all tested magnitudes. The left hemisphere patient’s responses were more appropriately scaled for both rotation directions, falling in the low-normal range. These findings suggest that there is some degree of hemispheric specialization in the cortical processing of dynamic head rotations in the yaw plane. In this view, right hemisphere structures play a dominant role, processing rotations in both directions, while left hemisphere structures process rotations only toward the contralesional hemispace. © 2006 Elsevier Ltd. All rights reserved. Keywords: Self-motion; Updating; Path integration; Manual pointing; Spatial cognition The vestibular system plays a central role in a wide variety of perceptual and cognitive functions, including spatial orientation, postural stability, motion perception, and oculomotor control (Brandt & Dieterich, 1999; Dieterich et al., 2003; Suzuki et al., 2001). Despite the importance of vestibular signals for nor- mal perception and action, however, surprisingly little is known about how these signals are processed and represented at the cortical level. Although there is suggestive evidence that percep- tion of angular head motion in opposite directions may exhibit some degree of hemispheric specialization, the extent to which this might be true is currently unclear. The study presented here describes two patients (JM and TG) who suffered damage to key cortical and subcortical components of the vestibular network in the right and left hemispheres, respectively, and, therefore, ∗ Corresponding author. Tel.: +1 202 994 6313; fax: +1 202 994 1602. E-mail address: philbeck@gwu.edu (J.W. Philbeck). promises to provide insight into the perceptual representation of vestibular information in cortex. Vestibular signals travel from the VIIIth cranial nerve and vestibular nuclei to several nuclei in the thalamus, via the ros- tral midbrain; then from the thalamus, vestibular signals project directly or indirectly to several cortical structures (Berthoz, 1996; Brandt & Dieterich, 1999). In the monkey, these cortical regions include area 2v in the intraparietal sulcus; area 7, in the inferior parietal lobe; the ventral intraparietal region (VIP); the medial superior temporal and visual posterior Sylvian regions of the temporal lobe (MST and VPS); area 3aV, a sensorimo- tor region in the central sulcus; a region in the cingulate cortex; and a core region densely interconnected with nearly all of the foregoing regions, known as the parieto-insular vestibular cor- tex (PIVC) (Guldin & Gr ¨ usser, 1998). The PIVC is located near the posterior end of the insula in the depths of the lateral sulcus. In humans, the cortical vestibular structures are known with less certainty, but evidence from a variety of sources (principally 0028-3932/$ – see front matter © 2006 Elsevier Ltd. All rights reserved. doi:10.1016/j.neuropsychologia.2006.02.004 NSY-2232; No. of Pages 13