Differences in Hippocampal Volume among Food Storing Corvids

Abstract

The hippocampal complex (hippocampus and parahippocampalis) is known to play a role in spatial memory in birds and is known to be larger in food-storing versus non-storing birds. In the present study, we investigated the relative volume of the hippocampal complex in four food-storing corvids: gray-breasted jays (Aphelocoma ultramarina), scrub jays (Aphelocoma coerulescens), pinyon jays (Gymnorhinus cyanocephalus), and Clark's nutcrackers (Nucifraga columbiana). The results show that Clark's nutcrackers have a larger hippocampal complex, relative to both body and total brain size, than the other three species. Clark's nutcrackers rely more extensively on stored food in the wild than the other three species. Clark's nutcrackers also perform better during cache recovery and operant tests of spatial memory than scrub jays. Thus, greater hippocampal volume is associated with better performance in laboratory tests of spatial memory and with stronger dependence on food stores in the wild.

Is bigger always better? A critical appraisal of the use of volumetric analysis in the study of the hippocampus

“…However, the inclusion of recent data on western scrub-jays (Aphelocoma californica) shows that this picture may not be correct. Pravosudov & de Kort (2006) report Hp volumes (76.19 + 6.9 mm 3 ) more than two times larger than those previously reported for the species (32.06 + 3.6 mm 3 ; Basil et al 1996) and much larger than other North American corvids (figure 2). This is the case even though the scrub-jay is not thought to be a particularly prolific cacher (Vander Wall & Balda 1981).…”

On the Proper Definition of Cognitive Ethology

“…This is consistent with the possibility of important ontogenetic effects in the development of spatial memory in nutcrackers. Basil et al (1996) found that nutcrackers have larger hippocampi (adjusted for total brain size) than Pinyon Jays, Scrub Jays, or Mexican Jays, which are all corvids less dependent on cached food than nutcrackers. It is possible that the early experience effects suggested by Dimmick's work are expressed in increased hippocampal growth, as suggested by the findings of Basil et al Comparative experiments suggest even more.…”

“…For example, we know that species differences in hippocampal volume, adjusted for body or total brain size, correlate with dependence on cached food in parids and corvids (Krebs et al, 1989;, and especially in the case of seed-caching corvids, with performance on a variety of test of spatial cognition (Basil et at., 1996). However, hippocampal volume is a very global, unsatisfactory measure.…”

Memory in Food Caching Animals

“…Comparative studies of avian hippocampus have found that species that store food have a larger relative hippocampal size than those that do not (Krebs et al, 1989;Garamszegi and Eens, 2004;Lucas et al, 2004; but see Brodin and Lundberg, 2003). Correlations are also found between food storing behavior, spatial memory performance, and relative hippocampal volume for foodstoring birds within corvids (Healy and Krebs, 1992;Basil et al, 1996) and parids (Hampton et al, 1995;, as well as in food-storing rodents within the kangaroo rat family (Jacobs and Spencer, 1994).…”

“…For example, Pravosudov and de Kort (2006) analyzed the brains of a large number of scrub jays, which have been classified as storing fewer seeds (Balda and Kamil, 1989) and performing less accurately during many spatial memory tasks (e.g., Balda and Kamil, 1989;Olson, 1991, see previous); they have been found to have a smaller hippocampus than other food-storing corvids (Basil et al, 1996). Their data indicated a significantly larger relative hippocampal volume than the scrub jays in Basil et al (1996). This difference in results may be due to methodological differences (paraffin-embedded vs. frozen tissue).…”