English Language Summary of Krushinskaya 1966, by Anna Klintsova

Krushinskaya, N. (1966). Some Complex Forms of Feeding Behavior of Nutcracker Nucifraga caryocatactes, After Removal of Old Cortex. Z. Evoluz. Biochem. Fisiol. II, 563-568.

The following is an extended English language summary of the Krushinskaya 1966 paper, originally published in Russian. Readers should note that this is only a summary and interested persons should obtain full translations of the original article to ensure accuracy and detail.

This study examined the effects of various lesions on food-caching behavior in nutcrackers. The design of the experiment included eight nutcrackers, four experimental birds with lesions of the "old cortex" including the avian hippocampus, and four control birds. The control birds also received lesions and are divided into two subgroups, each containing two birds. Two of the controls received lesions of the neostriatum caudatum, while the remaining two controls received lesions of the hyperstriatum.

Behavioral testing was done in a large experimental chamber with the floor covered with moss. The birds were placed in the chamber and allowed to make 5-10 cache sites, where they buried seeds under the moss. The birds were then removed and placed in their home cages for 3 hrs, after which they were again placed in the experimental chamber and allowed to search for cached seeds. The number of cache recoveries, time to first recovery, and the number of digs in incorrect locations were recorded. The floor of the experimental chamber was drawn with a superimposed grid and the locations of caches, digging sites, recoveries within 10-15 min., and recoveries within 3 hrs are shown in a diagram.

Results showed that although birds with old cortex lesions stored seeds normally, they were severely impaired in finding the seeds, recovering only 12% of seeds. Birds with control lesions of the neostriatum caudatum and hyperstriatum behaved normally, recovering 75-95% of seeds. Control birds took 7-10 min. to find their first cache, while birds with lesions of the old cortex took 1 hr, 35 min. to make their first recovery. The author notes that normal and control lesion birds go to a cache location, recover the seeds, and proceed to the next cache location, whereas birds with old cortex lesions first go to the location in the chamber where they previously received seeds from the experimenter, then appear to make a random search for caches. However, looking at the diagram of search sites shows that birds with old cortex lesions often searched in areas adjacent to cache sites, but also searched in some areas that were quite distant from cache sites. The author also notes that while birds with old cortex lesions were impaired in finding caches after 3 hrs, they did not appear to be impaired when allowed to search immediately after storing seeds.

Overall, this study and its results are quite remarkable and consistent with findings from studies of mammalian hippocampal function. I would recommend obtaining a complete translation to anyone interested in hippocampal function, avian behavior, or neuroethology of spatial memory.