Inferences on a Multidimensional Social Hierarchy Use a Grid-like Code

Abstract

Generalizing experiences to guide decision making in novel situations is a hallmark of flexible behavior. It has been hypothesized such flexibility depends on a cognitive map of an environment or task, but directly linking the two has proven elusive. Here, we find that discretely sampled abstract relationships between entities in an unseen two-dimensional (2-D) social hierarchy are reconstructed into a unitary 2-D cognitive map in the hippocampus and entorhinal cortex. We further show that humans utilize a grid-like code in several brain regions, including entorhinal cortex and medial prefrontal cortex, for inferred direct trajectories between entities in the reconstructed abstract space during discrete decisions.Moreover, these neural grid-like codes in the entorhinal cortex predict neural decision value computations in the medial prefrontal cortex and temporoparietal junction area during choice.Collectively, these findings show that grid-like codes are used by the human brain to infer novel solutions, even in abstract and discrete problems, and suggest a general mechanism underpinning flexible decision making and generalization.

Protocol for building a cognitive map of structural knowledge in humans by integrating abstract relationships from separate experiences

“…Our same protocol could instead be administered to have subjects construct a unitary 2-D cognitive map of a single social hierarchy learned from piecemeal pairwise comparisons. The following is the altered protocol for the studies ( Park et al., 2020b ) in which participants learned the relative status of 16 individuals in a combined 4 × 4 social hierarchy structure in two dimensions (not two groups of social hierarchies).…”

“…We performed a placement task in a separate group of participants who did not participate in the following fMRI experiment to ensure the participants for fMRI experiments were never asked to solve the task spatially ( Park et al., 2020a ). Alternatively, to examine the internal representation of the cognitive map of the fMRI participants with the placement task, it should be performed after finishing the fMRI experiment ( Park et al., 2020b ).

Figure 3 Expected results of the behavioral training (A) An example screen of the placement task.

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“…In Park et al. ( Park et al., 2020b ), participants have learned the relationship of 16 individuals together. They learned the hierarchical relationship in each of two dimensions on different days.…”

“…For the first study in which we needed to control the training experiences to be the same across participants ( Park et al., 2020a ), we did not train low performance participants after day 3. However, in the second study ( Park et al., 2020b ), we let participants continue training over multiple days until reaching a high threshold, which could help to increase the retention rate. This suggests that further training in the first study would have likewise resulted in improved performance for many subjects and would therefore increase the retention rate, if desirable and equating experience across subjects is not deemed necessary for the experimental goals.…”

“…For complete details on the use and execution of this protocol, please refer to Park et al. (2020a , 2020b) .…”