Neuron 59, 125–137 (2008)

Researchers studying anaesthetized adult gerbils fitted with earphones report that the neurotransmitter GABA calibrates the processing system that locates a sound's origin.

Ursula Koch and Anna Magnusson of LMU Munich in Germany and their co-workers considered the lateral superior olive (LSO), a nucleus in the gerbil brainstem where information from both ears converges. They played different sound volumes through the right and left earphones and administered chemicals that stimulate or block GABA receptors. This revealed that GABA released by neurons in the LSO adjusts the balance of excitation and inhibition experienced by the same neurons as a result of signals from each ear.

Excitatory nerve terminals seemed to be more strongly affected by GABA, which suggests that neurons in the LSO tend to 'turn down' excitatory input. This would increase auditory sensitivity on the side of the animal that a sound is coming from.