Pure Representational Neglect After Right Thalamic Lesion Ste ´phanie Ortigue, MS, 1 Isabelle Viaud-Delmon, PhD, 1 Jean-Marie Annoni, MD, 1 Theodor Landis, MD, 1 Christoph Michel, PhD, 1 Olaf Blanke, MD, 1 Patrik Vuilleumier, MD, 2 and Euge `ne Mayer, PhD 1 After a right thalamic stroke, an 86-year-old man pre- sented an acute pure left representational neglect in the absence of any perceptual neglect. On spatial mental im- agery tasks, the patient systematically omitted items lo- cated on his left side, but only when a vantage point was given. This suggests that (1) pure representational neglect is not just a residual finding after recovery from global (perceptual and representational) neglect; (2) space rep- resentation can be coded by two independent processes: in viewer-centered or world-based (allocentric) coordi- nates; and (3) the right thalamus serves as a relay in the processing of spatial visual imagery. Ann Neurol 2001;50:401– 404 Unilateral neglect is generally defined as an impaired ability to detect stimuli in the contralesional hemis- pace. Neglect can occur when a patient actually sees environmental space (perceptual neglect), but also when he imagines the space without being there (rep- resentational neglect). 1 Left and right hemispace can be defined with respect to viewer-centered and environment-centered or object-centered (allocentric) frames of reference. 2 Viewer-centered coordinates involve the ability to lo- cate objects with reference to the subject’s own body, 3 whereas allocentric coordinates determine where some- thing lies in the world with reference to the environ- ment itself. 4 The allocentric frame of reference implies that relationships among multiple landmarks are coded and stored independently of the position of the sub- ject’s body. Perceptual neglect is typically based on viewer-centered frames of reference, 5 although relative environment-centered coordinates may also be in- volved. 6,7 Representational neglect may similarly in- volve both viewer-centered and allocentric coordinates; mental imagery could preferentially operate on stored representations independent of the viewer position. However, to our knowledge, viewer-centered and allo- centric coordinate frames have not yet been dissociated in representational neglect. Pure representational ne- glect, confined to internally generated representations of visual images 8 –11 is much less frequent than percep- tual neglect with 1,12–15 or without 2,8,12 representa- tional neglect. Because in 1 patient, representational neglect appeared as a pure deficit only after an initially concomitant perceptual neglect recovered, representa- tional neglect has been considered as a dynamic phe- nomenon of recovery from a global (perceptual and representational) neglect syndrome. 12 Finally, there is also evidence that representational and perceptual ne- glect might be dissociated with respect to lesion loca- tion. 8,9 However, pure representational neglect has only been described following cortical lesions. Here, we describe a patient who presented a pure left represen- tational neglect following a right thalamic infarction. Patient and Methods This 86-year-old right-handed man suffered from an acute onset of dysarthria and a moderate left hemiparesis without hemisensory loss, which recovered completely within 2 weeks. Magnetic resonance imagine (MRI) 1 week after ad- mission showed a recent right thalamic ischaemic lesion in the dorsomedial nucleus of the thalamus extending into the pulvinar (Fig 1). On admission, the patient was oriented and aware of his motor deficit. A detailed neuropsychological examination on the fifth day was normal except for impairment in figural fluency 16 and a strong left representational neglect. There was no perceptual neglect and no tactile, auditory, or visual extinction. Mental imagery outside the spatial domain was unaffected: drawing and verbal description from memory of objects and animals, oral spelling tasks, and a body imagery test 10 were flawless. All tasks were administrated on several occasions from the fifth day after admission. A general neuropsychological examination revealed that the patient had no aphasic deficit and no clinical deficit in long-term memory (percentile 50 on the Buschke Selective Reminding Test; percentile 10 on Rey’s signs). In short-term memory, his scores were in the normal range (percentile 75 on the digit span; percentile 50 on the Corsi block-span). His performance was in the lower range (percentile 25) on the Topographical Recognition Memory subtest of the Cam- den Memory Tests, and in the normal range in the Benton Visual Discrimination Test (41 of 54). Assessment of Perceptual Neglect In order to examine neglect in extrapersonal space, 17 four different tasks were given both in near (NS) and far (FS) space 18 : a line bisection task and three cancellation tasks with letters, digits, or lines. In addition, other tasks were given in From the 1 Functional Brain Mapping Laboratory and Neuropsycho- logical Unit, Department of Neurology, University Hospital of Ge- neva, Switzerland; and 2 Institute of Cognitive Neuroscience, Uni- versity College London, London, United Kingdom. Received Feb 26, 2001, and in revised form Jun 4. Accepted for publication Jun 4, 2001. Published online Aug 3, 2001; DOI: 10.1002/ana.1139 Address correspondence to Dr Ortigue, Functional Brain Mapping Laboratory, Department of Neurology, Geneva University Hospital, 24 rue Micheli-du-Crest, CH-1211 Geneva 14, Switzerland. E-mail: stephanie. ortigue@hcuge.ch BRIEF COMMUNICATIONS © 2001 Wiley-Liss, Inc. 401