Conserved spatial memory mechanisms
Food-caching birds are memory specialists that can remember thousands of hidden food items. Using electrophysiological recordings from freely behaving birds, Payne et al. analyzed neuronal activity in the likely hippocampus homolog of two bird species, the tufted titmouse and the zebra finch. They chose these two species to compare, respectively, birds that do and do not display food-caching behavior. Place cells and typical hippocampal firing patterns that resembled rodent neuronal activity could be detected in the extreme memory specialists. Compared with titmice, however, spatial activity was noticeably weaker and less abundant in zebra finches. These findings provide evidence that the neural processes underlying spatial memory are remarkably conserved across widely divergent hippocampal circuits separated by millions of years of evolution.
Science, abg2009, this issue p. 343
Spatial memory in vertebrates requires brain regions homologous to the mammalian hippocampus. Between vertebrate clades, however, these regions are anatomically distinct and appear to produce different spatial patterns of neural activity. We asked whether hippocampal activity is fundamentally different even between distant vertebrates that share a strong dependence on spatial memory. We studied tufted titmice, food-caching birds capable of remembering many concealed food locations. We found mammalian-like neural activity in the titmouse hippocampus, including sharp-wave ripples and anatomically organized place cells. In a non–food-caching bird species, spatial firing was less informative and was exhibited by fewer neurons. These findings suggest that hippocampal circuit mechanisms are similar between birds and mammals, but that the resulting patterns of activity may vary quantitatively with species-specific ethological needs.