Dynamic spatial sensitivity in auditory cortex

Abstract

Location is a conspicuous attribute of a sound source. The well-known cortical maps of space in the visual and somatosensory systems might lead one to search for a map of sound-source locations in the auditory cortex. That turns out to be a fool’s errand. The best efforts of our group and of others have failed to discover a point-to-point map of space in the auditory cortex, although such maps are found in the midbrain. Instead, we find that single neurons in the auditory cortex are broadly tuned for source location, with location-specific firing patterns that represent sound-source locations panoramically. Moreover, the spatial tuning of neurons is dynamic, sharpening when an animal is engaged in a localization task or, even more so, when competing sound streams are present. Despite the 180-to-360-degree spatial receptive fields of cortical neurons, a spatial stream segregation task demonstrated quantitatively similar ∼5–10 deg spatial resolution among human and cat psychophysics and cat cortical neuron responses. Our early failure to find a cortical space map reflects a feature, not a defect. We now appreciate that the panoramic and dynamic properties of cortical neurons are well adapted to the demands of auditory spatial perception.