Behavioural Brain Research 317 (2017) 88–94 Contents lists available at ScienceDirect Behavioural Brain Research journal homepage: www.elsevier.com/locate/bbr Research report Impaired perception of human movements in Parkinson’s disease Silvie Kloeters, Christian J. Hartmann, Viktoria D. Pundmann, Alfons Schnitzler, Martin Südmeyer, Joachim Lange ∗ Medical Faculty, Institute of Clinical Neuroscience and Medical Psychology, Heinrich Heine-University Düsseldorf, Germany highlights • Theories have linked motor execution and observation. • Parkinson patients are impaired in motor execution. • We hypothesized that Parkinson patients should be impaired in observation of human movements. • Results confirm the hypothesis that Parkinson patients are impaired in biological motion perception. article info Article history: Received 27 April 2016 Received in revised form 30 August 2016 Accepted 3 September 2016 Available online 5 September 2016 Keywords: Biological motion Point-light displays Motor system abstract Interacting with other individuals in a social world requires fast and accurate perception of other indi- viduals’ identity, actions, or intentions. Humans are very efficient in these social tasks, as they can extract social information even if the actor is represented only by a handful of point-lights on an otherwise invisi- ble body. Theories have argued that efficient visual perception of actions is based on intact motor system functioning. The motor system provides visuo-motor action representations shaped by the observer’s own movements or motor repertoire. If the observer’s motor repertoire is impaired, this should lead to impaired visuo-motor representations and ultimately to impaired visual perception of movements. Here we tested this hypothesis in a behavioral study with patients suffering from Parkinson’s disease (PD). PD patients are typically impaired in movement execution. We tested these patients and a matched control group in a visual discrimination task on human movement perception. The results showed that PD patients were significantly impaired in the perception of human movements. This impairment was most prominent for transitive (object-related) movements. The results indicate that impaired movement execution critically influences movement perception. The results support the hypothesis that the motor system plays a causal role for the visual perception of human movements. © 2016 Elsevier B.V. All rights reserved. 1. Introduction Perceiving and interpreting the movements and actions of other individuals is an important aspect for human social interaction [1,2]. Thus, it is not surprising that humans are very accurate and efficient at recognizing other peoples’ movements or gestures. It has been demonstrated already more than 40 years ago that observers can easily recognize the actions of other individuals even if the to-be-observed human body is depicted by only a handful light dots on an otherwise invisible body [3]. The sparse informa- tion of these so-called point-light displays has been shown to be sufficient to recognize gender, identity, or mood of the actor [4–6]. ∗ Corresponding author at: Medical Faculty, Institute of Clinical Neuroscience and Medical Psychology, Heinrich Heine-University Düsseldorf, Germany. E-mail address: Joachim.lange@med.uni-duesseldorf.de (J. Lange). Despite many years of research and increasing knowledge about the perception of human movements, the neuronal mechanisms are still not fully understood. While there is mounting evidence that the superior temporal sulcus (STS) and lateral occipito-temporal cortex (LOTC) are critically involved in the process of perceiving human movements [7,8], also other cortical areas have been shown to play a role for the perception of human movements. For exam- ple, areas of the motor system, which are typically involved in the execution of movements, have been associated also with move- ment perception [9][e.g. 9]. In this regard, theories have postulated a link between movement perception and execution of movements [10]. These theories have been supported by behavioral studies demonstrating interference between visual perception of a move- ment and the observer’s own movement or movement capabilities. For example, compared to stationary observers, walking observers were impaired in judging the walking speed of animated persons [11]. Similarly, it has been shown that self-generated movement http://dx.doi.org/10.1016/j.bbr.2016.09.009 0166-4328/© 2016 Elsevier B.V. All rights reserved.