LAUSR

Subpopulations of neurons fire at specific geographical locations, providing a mental map of an animal's position in space. The finding that the circuitry can also support auditory maps sheds light on the neuronal structure of cognition. See Letter p.719 Map-like representations of physical space have been well-documented in the hippocampus by studies of spatial navigation, but it is unclear whether this spatial representation is part of a more general mechanism for encoding other continuous variables, such as sound. Here, David Tank and colleagues recorded from rat hippocampal neurons while they manipulated a joystick to control sound output along a continuous frequency scale. Neurons encoded for all aspects of this task and formed discrete firing fields in response to specific sound frequencies. The hippocampal cells representing this auditory axis overlapped with cells representing space during navigation. The authors suggest that representation mechanisms similar to those used during navigation may encode variables in a broader range of cognitive processes.