Hippocampal volume has been associated with impaired & expert navigation, but large pre-registered studies found no such correlation in healthy adults; network models offer greater explanatory power for flexibility & individual differences

Hippocampal volume and navigational ability: The map(ping) is not to scale. Steven M. Weisberg, Arne D. Ekstrom. Neuroscience & Biobehavioral Reviews, March 17 2021. https://doi.org/10.1016/j.neubiorev.2021.03.012

Rolf Degen's take: The way things are, we will probably never learn whether taxi drivers really have a larger hippocampus, as shaky science findings once seemed to show

Highlights

• Hippocampal volume has been associated with impaired and expert navigation.

• Large pre-registered studies found no such correlation in healthy adults.

• Theoretical mechanisms supporting structure-behavior associations are tenuous.

• Navigation is a complex cognitive function, involving multiple brain networks.

• Network models offer greater explanatory power for flexibility and individual differences.

Abstract: A critical question regards the neural basis of complex cognitive skill acquisition. One extensively studied skill is navigation, with evidence suggesting that humans vary widely in navigation abilities. Yet, data supporting the neural underpinning of these individual differences are mixed. Some evidence suggests robust structure-behavior relations between hippocampal volume and navigation ability, whereas other experiments show no such correlation. We focus on several possibilities for these discrepancies: 1) volumetric hippocampal changes are relevant only at the extreme ranges of navigational abilities; 2) hippocampal volume correlates across individuals but only for specific measures of navigation skill; 3) hippocampal volume itself does not correlate with navigation skill acquisition; connectivity patterns are more relevant. To explore this third possibility, we present a model emphasizing functional connectivity changes, particularly to extra-hippocampal structures. This class of models arises from the premise that navigation is dynamic and that good navigators flexibly solve spatial challenges. These models pave the way for research on other skills and provide more precise predictions for the neural basis of skill acquisition.

Keywords: Hippocampusspatial navigationMRIfunctional connectivitybrain volume