Hippocampal lesions in homing pigeons do not impair feature-quality or feature-quantity discrimination

Abstract

The role of the avian hippocampal formation (HF) in spatial cognition is well demonstrated. However, it remains uncertain if the avian hippocampus, like its mammalian counterpart, has a role in the integration of elements that could compose a memory independent of space. The two experiments in the current study examined whether the HF of homing pigeons (Columba livia) was required to encode into memory a discriminative representation of food quality (Experiment 1) and quantity (Experiment 2) with different food bowl-features. Pigeons were exposed to an array of different colored bowls, two of which contained food rewards differing in preferred quality or quantity. To render space irrelevant for memory encoding, the location of the food-rewarded bowls was altered between each trial, while the features of the rewarded bowls remained constant. Both groups learned the feature-based quality and quantity discrimination tasks and no difference in performance between control pigeons and those with bilateral lesions of the hippocampus were found. The findings do not support the hypothesis that the avian HF is recruited when only non-spatial elements are integrated into a unified memory. From the current study, and the literature as a whole, it appears that the avian HF, unlike the mammalian hippocampus, may play no necessary role in memory processes where space is irrelevant.