The neural basis of ego- and allocentric reference frames in spatial navigation: evidence from spatio-temporal coupled current density reconstruction.

Different strategies in spatial navigation during passages through computer-simulated tunnels were investigated by means of EEG source reconstruction. The tunnels consisted of straight and curved segments and provided only visual flow, but no landmark, information. At the end of each tunnel passage, subjects had to indicate their end position relative to the starting point of the tunnel. Even though the visual information was identical for all subjects, two different strategy groups were identified: one group using an egocentric and the other group an allocentric reference frame. The current density reconstruction revealed the use of one or the other reference frame to be associated with distinct cortical activation patterns during critical stages of the task. For both strategy groups, an occipito-temporal network was dominantly active during the initial, straight tunnel segment. With turns in the tunnel, however, the activation patterns started to diverge, reflecting translational and/or rotational changes in the underlying coordinate systems. Computation of an egocentric reference frame was associated with prevailing activity within a posterior parietal-premotor network, with additional activity in frontal areas. In contrast, computation of an allocentric reference frame was associated with dominant activity within an occipito-temporal network, confirming right-temporal structures to play a crucial role for an allocentric representation of space.