Please cite this article in press as: Sautter CS, et al. Dynamic visual information plays a critical role for spatial navigation in water but not on solid ground. Behav Brain Res (2008), doi:10.1016/j.bbr.2008.07.006 ARTICLE IN PRESS G Model BBR-5554; No. of Pages 4 Behavioural Brain Research xxx (2008) xxx–xxx Contents lists available at ScienceDirect Behavioural Brain Research journal homepage: www.elsevier.com/locate/bbr Short communication Dynamic visual information plays a critical role for spatial navigation in water but not on solid ground Chiara Sajidha Sautter a,b,c,∗ , Luca Cocchi a,b,d , Franc ¸ oise Schenk a,b,c a Department of Physiology, University of Lausanne, Switzerland b Center of Psychiatric Neuroscience (CNP), University of Lausanne, Switzerland c Institute of Psychology, University of Lausanne, Switzerland d Melbourne Neuropsychiatric Centre, University of Melbourne, Australia article info Article history: Received 27 May 2008 Received in revised form 30 June 2008 Accepted 2 July 2008 Available online xxx Keywords: Spatial learning Visual flow Proprioception Morris water maze Homing board abstract In the Morris water maze (MWM) task, proprioceptive information is likely to have a poor accuracy due to movement inertia. Hence, in this condition, dynamic visual information providing information on linear and angular acceleration would play a critical role in spatial navigation. To investigate this assumption we compared rat’s spatial performance in the MWM and in the homing hole board (HB) tasks using a 1.5Hz stroboscopic illumination. In the MWM, rats trained in the stroboscopic condition needed more time than those trained in a continuous light condition to reach the hidden platform. They expressed also little accuracy during the probe trial. In the HB task, in contrast, place learning remained unaffected by the stroboscopic light condition. The deficit in the MWM was thus complete, affecting both escape latency and discrimination of the reinforced area, and was thus task specific. This dissociation confirms that dynamic visual information is crucial to spatial navigation in the MWM whereas spatial navigation on solid ground is mediated by a multisensory integration, and thus less dependent on visual information. © 2008 Published by Elsevier B.V. 1. Introduction Spatial learning relies on the integration of different redundant spatial cues, none of which being absolutely necessary, except in controlled environments with a limited number of cues [11]. This multisensory integration mediates place learning in the Morris water maze (MWM) [9] or in a homing hole board (HB) [13]. In the MWM, rodents have to swim to an invisible escape platform, whereas in the HB, they walk to find a hidden escape hole con- nected to their home cage. In both tasks, the development of direct approach trajectories from any starting position is an indication of place learning [15]. Spatial discrimination and memory of the goal area is assessed from the time spent in visiting potential target posi- tions in the environment when the escape platform is absent or the hole unconnected. In the last decade, a large literature focused on rodent’s spatial memory and the role of the hippocampus in processing spatial rep- resentations (for a review see [17,10,7]). During exploratory bouts, the updating of the current position relative to a starting or to other ∗ Corresponding author at: Center of Psychiatric Neuroscience (CNP), Department of Psychiatry, Cery Hospital, Albatros Building, CH-1008 Prilly-Lausanne, Switzer- land. Tel.: +41 79 735 95 44; fax: +41 216436950. E-mail address: Chiara.Sautter@unil.ch (C.S. Sautter). reset position plays a critical role in the development of accurate spatial memory [7]. This representation is elaborated from the inte- gration of different locale views with movement-generated cues, mainly vestibular and proprioceptive ones. One might thus con- sider that the directional vector elaborated from path integration does more than merely allow the navigator to beeline to the start of the journey and contributes to the elaboration of the cognitive map [8]. Rats learn to discriminate a target place on solid ground and in the water as well [15]. However, some of the underlying mecha- nisms might be different depending on the mode of locomotion. This is evident in a differential susceptibility of the two tasks to cue removal. In the MWM, rats showed little learning if they had no view of the illuminated room during the middle segment of the escape swim [19] or if the light was turned off each time the animal entered the central region of the MWM [1]. However, in a similar experiment conducted in the HB, rats could orient without perma- nent access to distant spatial cues [15] and they expressed accurate spatial discrimination in a curtained area in which they were free to enter from a peripheral platform with access to the room panorama. Visual information might thus be more crucial for the development of accurate place navigation in the MWM than in the HB. More precisely, we hypothesized that dynamic visual information, e.g., visual flow and size change in visual cues as rats swim toward or away from them, might be critical for navigation in the water. They 0166-4328/$ – see front matter © 2008 Published by Elsevier B.V. doi:10.1016/j.bbr.2008.07.006