The neuroscience of remote spatial memory: A tale of two cities

K.C. was impaired in remembering minor landmarks and perceptual details of familiar environments, despite largely intact visuoperceptual processing abilities and semantic knowledge of those same places.

“K.C. was impaired, however, in remembering minor landmarks and perceptual details of familiar environments, despite having largely intact visuoperceptual processing abilities and semantic knowledge of those same places.”

K.C., an individual with bilateral HPC damage, could produce accurate sketch maps of the overall layout of his hometown and judge relative distances and directions between its major landmarks.

“This was demonstrated in the case K.C., an individual with bilateral HPC damage, who could produce accurate sketch maps of the overall layout of his hometown (Fig. 3) and judge relative distances and directions between its major landmarks 27,81,82 .”

Schematic aspects of remote spatial memories are those features that survive HPC damage and continue to support navigation.

“Schematic aspects of remote spatial memories are those features that survive HPC damage and continue to support navigation 27,80 .”

Schematized spatial memories primarily include geometric properties rather than surface properties.

“Schematized spatial memories primarily include geometric properties [G], rather than surface properties [G] 27,70,80,83 .”

The posterior HPC supports detailed cognitive maps, whereas a network of extra-HPC regions including PHC, RSC and PPC supports cognitive maps transformed over repeated experiences into a spatial gist.

“Thus, whereas the (posterior) HPC seems to support detailed cognitive maps, a network of extra-HPC regions, including the parahippocampal cortex (PHC), RSC and PPC, seems to support cognitive maps that have been transformed over repeated experiences navigating in a particular environment to form a 'spatial gist' -a summary of a specific environment 25,27,127,128 .”

Many of the same extra-HPC regions involved in the initial acquisition of spatial knowledge for large-scale environments are also involved in the retrieval of schematized spatial memory and event schemas, suggesting that the core elements of spatial schemas may be laid down at acquisition.

“fMRI studies indicate that many of the same extra-HPC regions involved in the initial acquisition of spatial knowledge for large-scale environments are also involved in the retrieval of schematized spatial memory 27,83,128 and event schemas 22 , suggesting that the core elements of spatial schemas may be laid down at acquisition 92,[147][148][149][150] .”