These patterns of neuronal activity were found in the three areas of the cat auditory cortex that the authors studied. Although such broadly tuned neurons, by definition, cannot individually encode locations with high precision, it is clear from the authors' model that the most accurate aural discrimination occurs where neuron activity changes abruptly, that is, at the midpoint between both ears-a transition zone between neurons tuned to sounds coming from the left and those tuned to sounds coming from the right. In their alternative model, groups of neurons that are broadly responsive to sounds from the left or right can still provide accurate information about sounds coming from a central location. In a new study, Christopher Stecker, Ian Harrington, and John Middlebrooks find evidence to support such a population code. What's more, electrophysiological recordings in mammals indicate that most neurons show the highest response to sounds emanating from the far left or right and that few neurons show that kind of response to sounds approaching head-on-even though subjects are best at localizing sounds originating in front of them.įaced with such contrary evidence, other investigators have suggested that sound localization may rely on a different kind of code-one based on the activity distributed over large populations of neurons. Discriminating sound locations from neural dataĮvidence for local coding of auditory space has been shown in the brains of owls and in a subcortical region of small mammals, but no such map has been found in the higher centers of the mammalian auditory cortex.
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