Click vs. click-click vs. blink-click: Factors influencing human
sound localization in the horizontal plane

Norbert Kopco
Department of Cybernetics and AI, Technical University, Kosice, Slovakia
Department of Cognitive and Neural Systems, Boston University

The basic brain processing that underlies horizontal sound
localization is well understood: the binaural cues of interaural
level and time difference are extracted in the auditory brainstem,
and later combined to determine the perceived location of the
source that produced the sound. This talk will review three
behavioral experiments that explored various factors influencing
this process of conversion of binaural cues to spatial auditory
percepts.

In the first experiment, temporal factors were explored by
examining the effect of a preceding distractor on the
target sound localization. Strong effects were observed, even for
the distractor-target onset asynchronies of several hundred
milliseconds. The effects were influenced by the presence of
reverberation, by perceptual organization, as well as by long-term
contextual plasticity of the spatial auditory maps.

In the second experiment, the ventriloquism effect (i.e.,
visually-induced spatial auditory plasticty) was used to
explore the coordinate system in which the auditory space is
represented in the brain. The results suggest that head-centric,
rather than eye-centric, coordinate system is used, at least in the
primates.

Finaly, the third experiment explored the effect of a preceding
informative cue on sound localization performance. While auditory
cue had a very little influence, a visual cue had a strong effect,
biasing perception in the oposite direction compared to the
auditory cue. This result suggests that the control of auditory
spatial attention is modality dependent, and that it occurs on the
time scales of seconds.