Please cite this article in press as: Durán E, et al. Lateral but not medial telencephalic pallium ablation impairs the use of goldfish spatial allocentric strategies in a “hole-board” task. Behav Brain Res (2010), doi:10.1016/j.bbr.2010.06.010 ARTICLE IN PRESS G Model BBR-6576; No. of Pages 8 Behavioural Brain Research xxx (2010) xxx–xxx Contents lists available at ScienceDirect Behavioural Brain Research journal homepage: www.elsevier.com/locate/bbr Short communication Lateral but not medial telencephalic pallium ablation impairs the use of goldfish spatial allocentric strategies in a “hole-board” task Emilio Durán ∗ , Francisco M. Oca ˜ na, Cristina Broglio, Fernando Rodríguez, Cosme Salas Laboratory of Psychobiology, Campus Santiago Ramón y Cajal, University of Sevilla, Sevilla, Spain article info Article history: Received 29 March 2010 Received in revised form 28 May 2010 Accepted 14 June 2010 Available online xxx Keywords: Spatial cognition Hole-board task Goldfish Allocentric navigation Telencephalon Lateral pallium Medial pallium abstract Strong evidence suggests that the ventral region of the lateral telencephalic pallium of teleost fish, a structure involved in allocentric spatial cognition, is homologous to the hippocampus of tetrapods. This homology was first proposed on basis of anatomical data, and subsequently confirmed by developmental, functional and behavioural studies. Nonetheless, Saito and Watanabe [30,32] claim that not the lateral but, rather, the medial pallium participates in goldfish spatial navigation and should be considered the homologue of the hippocampus. Here, we further investigate the effects of selective pallial lesions on the spatial cognition abilities of goldfish, trained in a “hole-board” analogue task, to find the baited feeder within a 5 × 5 feeder matrix surrounded by visual cues. The task in the present experiment is similar to that used by Saito and Watanabe, but including thorough probe tests that enabled to define clearly the spatial strategies employed by the animals, and, therefore, the spatial deficits caused by the pallial lesions. The results showed that the lateral, but not the medial pallium lesions, produced a dramatic impairment in the implementation of allocentric spatial strategies. Thus, only lateral pallium lesioned goldfish, like hippocampus lesioned tetrapods, failed to reach the goal when the cues in its proximity were excluded, indicating that they used a guidance strategy. These results do not replicate Saito and Watanabe’s, but are consistent to previous data indicating a close functional similarity between the lateral pallium of teleost fish and the hippocampus of amniotes. © 2010 Elsevier B.V. All rights reserved. 1. Introduction The lateral telencephalic pallium (LP) of teleost fish is selectively involved in the encoding of map-like representations as indicated by lesion and functional studies [3,4,29,35,36,40]. For example, lesions restricted to the LP produce severe place memory impair- ments in goldfish trained in a plus-maze surrounded by distal visual cues [29]. Following surgery, LP-lesioned fish show a severe and permanent deficit in identifying a familiar place (goal location) not only when reaching the goal requires implementing new routes (transfer trials), but also when the familiar trajectories are available (training trials). This impairment is as profound as that produced by the ablation of the whole telencephalon [11,17,33,34], and seems to affect selectively the allocentric memory system, as damage to LP does not disrupt cue learning or other egocentrically referenced strategies [29]. In fact, selective lesions to the dorsal (DP) or the medial (MP) pallium do not produce any observable impairment in spatial cognition [29]. The effects of LP lesions on goldfish spatial ∗ Corresponding author at: Laboratorio de Psicobiología, Facultad de Psicología, C/Camilo José Cela s/n, 41018 Sevilla, Spain. Tel.: +34 954557746, fax: +34 954557752. E-mail address: durang@us.es (E. Durán). performance are entirely similar to those observed in medial cor- tex or hippocampus damaged land vertebrates trained in spatial tasks that require the implementation of map-like representations [1,5,10,12,14,18,19,29,35,37,39]. The role of the teleostean LP in spatial cognition is evidenced also by the selective increase in the transcriptive activity of the neurons in the ventral part of the lateral telencephalic pallium of goldfish after learning a spatial constancy task [4,40]. All these data concerning the involvement of the lateral pal- lium of goldfish in the place memory system are consistent with the expected topological position of the hippocampal pallium in ray-finned fishes given that the embryonary development of the telencephalon occurred by an eversion process. Eversion results in the medial-to-lateral reversal of the topographical position of the dorsal pallium zones, such that, for instance, the area equivalent to the medial (hippocampal) pallium of evaginated telencephalons occupies a lateral position in the telencephalic pallium of the actinopterygian fish [2,6,7,20,21,22,23]. Particularly, the ventral subdivision of the telencephalic pallium lateral division (Dlv) is considered the most likely candidate as the specific homologue of the medial pallium or hippocampus in tetrapods, on the basis of the pattern of connectivity and other anatomical and developmen- tal considerations [24,25,42,44]. The homology of both structures is supported also by the similarity in the distribution pattern of 0166-4328/$ – see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.bbr.2010.06.010