Mental search of concepts is supported by egocentric vector representations and restructured grid maps

Abstract

The human hippocampal-entorhinal system is known to represent both spatial locations and abstract concepts in memory in the form of allocentric cognitive maps. Using fMRI, we show that the human parietal cortex evokes complementary egocentric-like vector representations in conceptual spaces during goal-directed mental search, akin to those observable during physical navigation to determine where a goal is located relative to oneself. Concurrently, grid-like representations, a neural signature of allocentric cognitive maps in entorhinal, prefrontal, and parietal cortices, are restructured as a function of conceptual goal proximity, akin to rodent grid cells firing around reward locations during spatial exploration. These brain mechanisms might support flexible and parallel readout of where target conceptual information is stored in memory, capitalizing on complementary reference frames.

Altered grid-like coding in early blind people

“…Although our results could, in part, be related to the specifics of the clock environment, we show for the first time how early blindness can modulate the neural geometry of entorhinal grid maps, possibly by encouraging an egocentric perspective during navigation. Future studies should investigate differences in neural geometry patterns between sighted and early blind individuals during the navigation of different types of environments 89 , as well as during conceptual navigation in non-spatial domains of knowledge [90][91][92][93][94] across complementary egocentric and allocentric reference frames 19 .…”

Spontaneous eye movements reflect the representational geometries of conceptual spaces

“…2 ). Indeed, recent empirical evidence indicates that when participants are engaged in goal-directed 'conceptual navigation', mentally searching for specific goal stimuli in their mind, their parietal cortex represents the navigated conceptual space using egocentric-like codes 66 . Crucially, this was associated with concurrent activation of the oculomotor system, which kept track of goal position in conceptual space from a first-person perspective.…”