The human parahippocampal cortex subserves egocentric spatial learning during navigation in a virtual maze

BackgroundPresent evidence suggests that the hippocampus (HC) and the parahippocampal cortex (PHC) are involved in allocentric (world-centered) spatial memory. However, the putative role of the PHC in egocentric (body-centered) spatial learning has received only limited systematic investigation.MethodsTo examine the role of the PHC in egocentric learning, 19 healthy volunteers learned to find their way in a virtual maze during functional magnetic resonance imaging (fMRI). The virtual maze presented a first-person view, lacked any topographical landmarks and could be learned only using egocentric navigation strategies.ResultsDuring learning, increased medial temporal lobe activity was observed in the PHC bilaterally. Activity was also observed in cortical areas known to project to the PHC and proposed to contribute to egocentric spatial navigation and memory.ConclusionsOur results point to a role of the PHC for the representation and storage of egocentric information. It seems possible that the PHC contributes to egocentric memory by its feedback projections to the posterior parietal cortex. Moreover, access to allocentric and egocentric streams of spatial information may enable the PHC to construct a global and comprehensive representation of spatial environments and to promote the construction of stable cognitive maps by translating between egocentric and allocentric frames of memory.     

Influence of spatial environment on maze learning in an African mole-rat

In subterranean species where excavation is energetically expensive, efficient spatial navigation is vital to reducing the costs of locating important resources such as food and mates. While spatial navigational ability is positively correlated with sociality in subterranean mammals, we have a less clear understanding of the role of habitat complexity on navigational ability. We tested spatial navigational ability and memory in 12-18-month captive Natal mole-rats (Cryptomys hottentotus natalensis) maintained in a simple environment with no environmental enrichment and newly captured wild individuals from natural, complex burrow systems. In maze trials, mole-rats captured freshly from the wild made significantly fewer navigational errors, were more likely to successfully navigate the maze, travelled shorter distances and as a consequence, completed the maze in less time. Male mole-rats from both experimental treatments were more likely to complete the maze than females. Memory retention of the maze was tested on day two, seven, 30 and 60, respectively. The results were variable, although both groups showed a significant memory retention 60?days after testing. Our results highlight the potential importance of the environment (microhabitat complexity) on spatial cognitive performance in mole-rats.