Fig. 2

Olfactory identification correlates with spatial memory. a The 4-on-8 Virtual Maze (4/8 VM) consists in an 8-arm radial maze surrounded by landmarks. In Part 1, four of the paths are blocked and four are open. Participants have to retrieve objects at the end of the open paths. In Part 2, the barriers are removed. Participants have to avoid the paths they visited in Part 1 to retrieve the remaining objects. They can learn the object locations using a spatial memory strategy (e.g., “the path is to the left of the boulder”) or a stimulus-response strategy (“From the starting position, I have to take the path straight ahead and then skip a path on the right”). Once participants learn the task to criterion, they are taken to a probe stage, where a wall is raised around the maze which hides the landmarks. People who used a spatial memory strategy during learning ('spatial learners') make more errors than people who used a stimulus-response strategy ('response learners'), as they can no longer use landmarks to find the target paths. At the end of the task, participants complete a verbal report, which serves to determine the strategy they used as well as the number of landmarks they used (e.g., “I used the rock and the tree to find the objects”) and noticed (e.g., “I saw a mountain but I did not use it”). b There was a negative correlation between olfactory identification and the average number of navigational errors made in Part 2 of the learning trials (r = −0.37, Bootstrap BCa 95% CI [−0.52, −0.21]). c When we looked within navigation strategies, we found that this effect was driven by spatial learners (left) (r = −0.57, Bootstrap BCa 95% CI [−0.77, −0.33]), while response learners did not show such a relationship (right) (r = −0.22, Bootstrap BCa 95% CI [−0.49, 0.14]). Thus, it appears that the relationship between olfactory identification and navigation is specific to those who use a hippocampal-dependent navigation strategy. In other words, olfactory identification correlates with spatial learning, but not with stimulus-response learning