# Brain Bases for Navigating Acoustic Features

## TL;DR

The study shows that navigating sound environments in the brain involves similar brain regions as physical navigation, including the hippocampus.

## Contribution

The research demonstrates that the hippocampus and related brain areas support navigation in non-spatial auditory dimensions.

## Key findings

- The hippocampus and auditory cortex are active during navigation in an acoustic dimension.
- Brain regions like the orbitofrontal cortex show increased activity when adjusting sound density toward a target.
- Navigation success correlates with activity in the hippocampus and inferior frontal gyrus.

## Abstract

Whether physical navigation shares neural substrates with mental travel in other behaviourally relevant domains is debated. With respect to sound, pure‐tone working memory in humans elicits hippocampal as well as auditory cortical and inferior frontal activity, and rodent work suggests that hippocampal cells that usually track an animal's physical location can also map to tone frequency when task‐relevant. We generated a sound dimension based on the density of random‐frequency tones in a stack, resulting in a percept ranging from low‐ (‘beepy’) to high‐density (‘noisy’). We established that unlike tone frequency, which listeners automatically associate with vertical position, this density dimension elicited no consistent spatial mapping. During functional magnetic resonance imaging, human participants held in mind the density of a series of tone stacks and, after a short maintenance period, adjusted further stacks to match the target (‘navigation’). Density of the currently heard sound was represented most strongly in bilateral non‐primary auditory cortex, specifically bilateral planum polare, whereas density of the maintained target was represented in right anterior hippocampus and left inferior temporal gyrus. Encoding and maintenance activity in bilateral hippocampus, inferior frontal gyrus, planum polare and posterior cingulate was positively associated with subsequent navigation success. Bilateral inferior frontal gyrus and hippocampus were among regions with elevated activity during adjustment, compared to a parity‐judgement condition with closely matched acoustics and motor demands. Bilateral orbitofrontal cortex was more active when navigation was toward a target density than when participants adjusted density in a control condition with no particular target. We find that self‐initiated travel along a non‐spatial auditory dimension engages a brain system overlapping with that supporting physical navigation.

Work in rodents suggests that navigation in physical space and the active analysis of sounds share a neural substrate in the hippocampus, supporting the use of common computational mechanisms.We examined the human brain system for navigation through an acoustic environment to a remembered target.In addition to high‐level auditory cortex we demonstrate involvement of the hippocampus in acoustic navigation along with other sites in frontal and cingulate cortex that also support physical navigation.

Work in rodents suggests that navigation in physical space and the active analysis of sounds share a neural substrate in the hippocampus, supporting the use of common computational mechanisms.

We examined the human brain system for navigation through an acoustic environment to a remembered target.

In addition to high‐level auditory cortex we demonstrate involvement of the hippocampus in acoustic navigation along with other sites in frontal and cingulate cortex that also support physical navigation.

We examined the human brain system for navigation to a remembered target through an acoustic environment defined by spectral density. We demonstrate the involvement of sites including the hippocampus and orbitofrontal cortex that also support physical navigation.