Spatial memory: Orientation study suggests that a visual image of the intermediate spatial environment exists in brain

This assumes, however, that the location in the brain is actually represented by explicit coordinates including a coordinate origin and metric distances. Following a study of pedestrians in Tübingen, however, Wolfgang Röhrich, Dr. Gregor Hardiess and Professor Hanspeter Mallot from the Institute for Neurobiology at the University of Tübingen suggest that another representation, based strongly upon visual representations, is involved. Their findings indicate that locations are stored in the brain simply as a collection or album of visual perspectives perceived during exploration.

In their experiments in downtown Tübingen the researchers approached pedestrians at special interviewing locations and asked them to draw a sketch of the Holzmarkt, a well-known square in the city centre. The Holzmarkt could not be seen directly from any of the interview locations. Ten interview locations were set up at a radius of some 150 meters around the Holzmarkt, and an additional four at a distance of about two kilometres from the Holzmarkt in small shopping centres. In the evaluation, only sketches by residents of Tübingen who had lived there for at least two years were used. The experiment was repeated in a comparable manner at various positions surrounding the Tübingen marketplace.

The sketches made by the passers-by at the ten nearby interview locations aligned to different compass directions. The distribution of sketch orientations of a given goal (Holzmarkt or Marktplatz) was different for different interview locations. "A more precise analysis showed that for each location, recall orientation is related to the respective direction of approach from the interview location to the goal," says Hanspeter Mallot. The dependence of recall orientation on interview location was not found, however, at the more distant locations. The authors conclude that locations are represented in the brain as visual perspectives: the participants of the experiment recalled the Holzmarkt by means of images of the Stiftskirche (a church), or of the exits from the Holzmarkt in the direction of the Marktplatz or Schulberg. In long-term memory all of these perspectives are available but in the "working memory" only those are available, in each case, which one would see when walking towards the Holzmarkt from each specific location. "Our study data indicates that the visuo-spatial memory of places which are not directly visible at any given moment has neither a coincidental nor a fixed orientation: rather, the remembered orientation depends on both the goal and the interview location."

The study's results are consistent with a visual model of memory of the spatial environment in the long-term and working memory. An abstract coordinate system, as a representation of the spatial environment in the brain, thus appears unnecessary. "In our model, the problem of coordinate transformation between memory types is reduced to the selection of the specific relevant view of a location," says the scientist.