Behavioural Brain Research 191 (2008) 153–163 Contents lists available at ScienceDirect Behavioural Brain Research journal homepage: www.elsevier.com/locate/bbr Research report Response properties of avian hippocampal formation cells in an environment with unstable goal locations Meghan C. Kahn a,∗ , Jennifer J. Siegel b , Tammy J. Jechura c , Verner P. Bingman a a Department of Psychology and J.P. Scott Center for Neuroscience, Mind, and Behavior, Bowling Green State University, Bowling Green, OH 43403, United States b Center for Learning and Memory, University of Texas at Austin, Austin, TX 78705, United States c Department of Psychology, Albion College, Albion, MI 49224, United States article info Article history: Received 10 January 2008 Received in revised form 13 March 2008 Accepted 16 March 2008 Available online 25 March 2008 Keywords: Pigeon Columba livia Hippocampus Spatial cognition abstract The response properties of 48 right (n = 24) and left (n = 24) hippocampal formation (HF) cells were exam- ined by recording from freely moving homing pigeons as they foraged in an open-field environment with unstable goal locations. Compared to previous results based on HF recordings from environments with stable goal locations, the spatial signal of the HF neurons recorded in the present study was substantially diminished; there was little indication of PATH cells found in previous HF recordings and nothing resem- bling place cells routinely recorded in rat hippocampus under similar conditions. However, lateralized response properties were detected. Right HF cells dramatically reduced their firing rates during a foraging session, resulting in very low reliability scores. By contrast, left HF cells maintained firing rates throughout sessions and displayed modestly higher reliability scores compared to right HF neurons. Notable was one striking group of cells (n =13), predominantly found in the right HF, that displayed rate maps character- ized by numerous, discrete areas of above baseline firing rates, overall very low firing rates and higher specificity than other cells recorded in this study. Overall, the data emphasize the importance of stable goal locations in shaping the spatial response profile of homing pigeon HF neurons and demonstrate the persistence of lateralized response properties under conditions when space explains little of the temporal variation in firing rate. © 2008 Elsevier B.V. All rights reserved. 1. Introduction The avian hippocampal formation (HF) plays a critical role in learning and remembering information about the location of objects in space [4,6,10,30,31,35]. Lesions to HF interfere with the ability of birds to learn to navigate through space [4,6] and result in the use of different spatial strategies [35,39]. Retrieval of spatial information is also impaired by damage to avian HF [10]. However, relatively little is known about how the activity of single HF neurons structure spatial representations in birds. Initial electrophysiological recordings from avian HF have pri- marily focused on understanding how single cells in HF are involved in representing space, with particular attention to comparisons with the place cells [25,27], and to a lesser extent head direction cells [36], found in the hippocampus and neighboring structures of rats. These studies showed that HF of freely moving pigeons contained cells whose firing properties appeared to be tied to rewarding aspects of the environment in addition to location in ∗ Corresponding author. Tel.: +1 419 372 4439. E-mail address: kahnmc@bgsu.edu (M.C. Kahn). an environment [14,15,33,34]. One type of cell described previ- ously was LOCATION cells, defined as cells that displayed one or more patches (adjacent pixels of significantly higher than average activity) that were maintained over time (reliable). Of interest, in a radial-arm maze, patches were disproportionately located at or near the places where food was consistently avail- able (76% of so-called LOCATION cells in [14]). Similarly, in a plus maze environment cells disproportionately increased firing rates at the ends of maze arms where food was delivered [33]. Many LOCATION cells rotated their fields of higher activity with rota- tion of local visual cues, demonstrating that position in space is important in determining the response properties of these cells [15]. Another group of cells fired selectively when an animal was moving between goal locations (so-called PATH cells in [14]). These cells exhibited reliable, elongated patches of higher than average activity along corridors that connected goal locations. Some PATH cells also displayed sensitivity to the directional heading of the ani- mal, only firing when an animal was either leaving or entering a maze arm [34]. Critically, both LOCATION and PATH cells displayed activity patterns that were stable over time [14,15,33,34], and were in that sense similar to the activity of rodent place cells [23]. 0166-4328/$ – see front matter © 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.bbr.2008.03.023