Behavioural Brain Research 89 (1997) 115 – 128 Research report Spatial learning induces neurogenesis in the avian brain Sanjay N. Patel a, *, Nicky S. Clayton a,b , John R. Krebs a a Departments of Zoology and Pharmacology, Uniersity of Oxford, Oxford, OX13PS, UK b Section of Neurobiology, Physiology and Behaior, Diision of Biological Sciences, Uniersity of California at Dais, Dais, CA 95616, USA Received 25 September 1996; received in revised form 13 March 1997; accepted 13 March 1997 Abstract It is known from previous work that neurones are born continuously in the ventricular zone of the bird brain. In this study, we show that the amount of cell proliferation in the ventricular zone of the hippocampus (HP) and the hyperstriatum ventrale (HV) is influenced by behavioural experience. Two groups of birds (marsh tits) were compared: those allowed to store and retrieve food once every 3 days between days 35 and 56, and age-matched controls treated in an identical way, except that they were not allowed to store and retrieve food. After three trials of storing and retrieval, between days 35 and 41 posthatch, experienced birds showed a significantly higher rate of cell proliferation than did controls. The experienced birds also showed a significant increase in total cell and neuronal number by day 56 posthatch, after eight trials of storing and retrieval. There were no significant differences in the amount of programmed cell death in the hippocampus in this study. In a novel analysis of the data we demonstrate that the effect of experience between days 35 and 41 was to increase the daily rate of neurogenesis in the ventricular zone from 3.9 to 10%, and that this change could account for the increase in total hippocampal neuronal number by day 56 in the experienced birds. Thus, the observed increase in hippocampal volume and neuronal number as a result of food storing and retrieval, may be caused by an increase in neurogenesis in the first few trials of food storing experience. © 1997 Elsevier Science B.V. Keywords: Learning; Memory; Food-storing; Hippocampus; Programmed cell death; Neurogenesis; Passerines 1. Introduction The avian hippocampus (HP) is known to play a role in spatial memory [1], including memory-based retrieval of food caches in food storing birds [2,3]. Experience of storing and retrieving food is associated with hippocampal enlargement and increased neuronal num- ber [4–6]. It is well established that cell proliferation in the adult avian brain occurs within the ventricular zone (VZ), from where newly born cells migrate into the brain and differentiate into neurons [7 – 16]. While glio- genesis is also thought to occur in situ within the parenchyma, neuronal cells are believed to originate only from within the VZ of the bird brain [7]. Hippocampal neuronal precursor cells are presumably located in the VZ that borders the HP in birds and which extends along the entire rostro-caudal extent of the HP (Fig. 1A). Changes in hippocampal neuronal number could therefore occur through modifications in the rate of cell proliferation within the hippocampal VZ, leading to a change in the rate of neurogenesis and/or through a variation in the amount of cell death within the HP. Here, we examined whether food storing and re- trieval behaviour can produce changes in the amount of cell proliferation in the hippocampal ventricular zone and in the amount of cell death within the hippocam- pus of a food catching bird, marsh tit, Parus palustris. * Corresponding author. Tel.: +44 1865 271151; fax: +44 1865 271221. 0166-4328/97/$17.00 © 1997 Elsevier Science B.V. All rights reserved. PII S0166-4328(97)00051-X