ORIGINAL PAPER Updating of Visual Space Across Horizontal Saccades in Cerebellar and Thalamic Lesion Patients Jutta Peterburs & Benno Koch & Michael Schwarz & Klaus-Peter Hoffmann & Irene Daum & Christian Bellebaum Published online: 24 April 2012 # Springer Science+Business Media, LLC 2012 Abstract Efference copies of motor commands are used to update visual space across saccades, ultimately ensuring transsaccadic constancy of space. Thalamic lesions have been shown to impair efference copy-based saccadic updat- ing in an oculomotor context, i.e., when two successive saccades are required. Moreover, the cerebellum has also been discussed as one possible source of saccade-related efference copy signals. The present study aimed to investi- gate the effects of thalamic and cerebellar lesions on sac- cadic updating in a perceptual context. To this end, seven patients with focal cerebellar lesions, seven patients with focal thalamic lesions and 11 healthy controls completed a perceptual localisation task in which the position of a target had to be updated across a single horizontal saccade, while saccade-related event-related potentials (ERPs) were recorded. Contrary to the expectations, localisation precision in both patient groups did not differ from the respective controls. A positive ERP component with centroparietal dis- tribution occurring from about 300 to 500 ms after saccade onset in the updating condition was observed equally pro- nounced in controls and thalamic lesion patients. In cerebellar lesion patients, there was evidence of a reduction of this relative positivity in the updating condition, particularly for leftward saccades. This finding suggests that cerebellar damage altered the neural processes underlying saccadic updating in a perceptual context without causing overt behav- ioural deficits. Keywords Saccades . Thalamus . Cerebellum . Efference copy . Spatial remapping . Event-related potentials Introduction While the saccadic system is a quite well-understood motor system, the sensorimotor integration processes needed to account for the perceptual consequences of eye movements—and thus ultimately for visual stability—are a matter of ongoing research. Efference copies of motor com- mands are thought to be used to update stimulus locations across eye movements [1], a process referred to as saccadic updating. In a series of ingenious experiments on monkeys, Sommer and Wurtz [2, 3] discovered a pathway conveying saccade-related efference copy signals from the superior colliculus (SC) via the mediodorsal thalamus (MD) to the frontal eye field (FEF) [2, 3]. Disrupting this pathway by injecting muscimol into MD led to very distinct behavioural deficits on a saccadic double-step task [4–6]. This task requires two successive saccades, the first of which can be executed in a visually guided fashion, whereas an efference copy of the first saccade’ s motor command is necessary for accurate programming of the second saccade, since posi- tional information about the target needs to be integrated with information about the positional displacement due to J. Peterburs (*) : I. Daum : C. Bellebaum Institute of Cognitive Neuroscience, Department of Neuropsychology, Faculty of Psychology, Ruhr University Bochum, Universitaetsstrasse 150, 44780 Bochum, Germany e-mail: jutta.peterburs@rub.de B. Koch : M. Schwarz Department of Neurology, Klinikum Dortmund, Beurhausstraße 40, 44137 Dortmund, Germany K.-P. Hoffmann Department of Neuroscience and Faculty of Biology and Biotechnology, Ruhr University Bochum, Universitaetsstrasse 150, 44780 Bochum, Germany Cerebellum (2013) 12:1–15 DOI 10.1007/s12311-012-0386-2