Rearing and Head Scanning as Functionally Equivalent Information-Seeking Behaviors
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Spatial memory is crucial for navigation and adapting to changing environmental conditions. Known neurophysiological mechanisms of spatial memory center on the importance of hippocampal activity and its spatial tuning. Yet, the behavioral strategies that support adaptive spatial encoding remain poorly understood. We have shown that dorsal hippocampal activity during rearing is necessary for spatial working memory, highlighting a role of information seeking behaviors for spatial memory encoding. Similarly, spatial tuning by dorsal hippocampal neurons is substantially updated during another information seeking behavior: attentive head scanning. However, the functional relationship between these behaviors is unknown. Here, to assess the relevance of environmental context for the expression of these behaviors, we quantified rearing and head scanning in a radial-arm-maze spatial working memory task while manipulating the height of the maze walls. Our goal was to test whether the stereotyped patterns of rearing that rats generate with tall walls are replaced with attentive head scanning when the walls are short enough to reach the top without rearing. We found that rats reared significantly less often when the walls were shortened and, instead, exhibited frequent attentive head scanning. The head scanning was done when and where the rats had previously exhibited stereotyped rearing. These results support the hypothesis that rearing and head scanning are functionally related behaviors. Future work should test two key inferences: 1) Head scanning is a critical epoch of spatial memory encoding, and 2) Spatial tuning by hippocampal neurons is updated during rearing.
Significance statement
Spatial memory is a core cognitive function, essential for healthy independent living. Though the hippocampus is critical for spatial memory, it remains unclear when and how. Separate prior studies link rearing and lateral head scanning to key periods of hippocampal processing, suggesting both behaviors support sensory information gathering for updating cognitive maps. However, their relationship is unresolved. Here, we test whether these behaviors are functionally interchangeable, with environmental structure determining expression. In a radial-arm maze, rats reared frequently with 21 cm walls but showed reduced rearing when walls were shortened to 4.6 cm, instead increasing head scanning at similar locations. These findings suggest rearing and head scanning share underlying motivations and provide a basis for comparing hippocampal activity during exploration.
