Article

Temporal stream of cortical representation for auditory spatial localization in human hemispheres.

Department of Speech and Cognitive Science, School of Medicine, University of Tokyo, 113-0033, Tokyo, Japan.
Neuroscience Letters (impact factor: 2.11). 11/2000; 292(3):215-9. pp.215-9
Source: PubMed

ABSTRACT We measured human evoked magnetic fields to binaural sounds with an interaural time delay as a cue for auditory localization. By analyzing the topography of auditory-evoked magnetic fields in the middle-latency, we demonstrated that particular cortical regions represent the direction of sound localization by their activity level. Upon presenting a binaural sound, the first representations were found in the middle frontal region as well as the superior temporal region of the right hemisphere approximately 19 ms after the stimulation, but their patterns differed. Other cortical regions including the prefrontal and parietal spatial areas were affected within roughly 60 ms. The results showed that the right hemisphere is dominant even in the preattentive stage of auditory spatial processing of sounds from different directions.

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    Article: Sound lateralization in subjects with callosotomy, callosal agenesis, or hemispherectomy.
    Markus Hausmann, Michael C Corballis, Mara Fabri, Aldo Paggi, Jörg Lewald
    [show abstract] [hide abstract]
    ABSTRACT: The question of whether there is a right-hemisphere dominance in the processing of auditory spatial information in human cortex as well as the role of the corpus callosum in spatial hearing functions is still a matter of debate. Here, we approached this issue by investigating two late-callosotomized subjects and one subject with agenesis of the corpus callosum, using a task of sound lateralization with variable interaural time differences. For comparison, three subjects with left or right hemispherectomy were also tested by employing identical methods. Besides a significant reduction in their acuity, subjects with total or partial section of the corpus callosum exhibited a considerable leftward bias of sound lateralization compared to normal controls. No such bias was found in the subject with callosal agenesis, but merely a marginal reduction of general acuity. Also, one subject with complete resection of the left cerebral cortex showed virtually normal performance, whereas another subject with left hemispherectomy and one subject with right hemispherectomy exhibited severe deficits, with almost total loss of sound-lateralization ability. The results obtained in subjects with callosotomy indicate that the integrity of the corpus callosum is not indispensable for preservation of sound-lateralization ability. On the other hand, transcallosal interhemispheric transfer of auditory information obviously plays a significant role in spatial hearing functions that depend on binaural cues. Moreover, these data are compatible with the general view of a dominance of the right cortical hemisphere in auditory space perception.
    Cognitive Brain Research 11/2005; 25(2):537-46. · 3.77 Impact Factor
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Keywords

activity level
 
auditory-evoked magnetic fields
 
binaural sound
 
cortical regions
 
different directions
 
human evoked magnetic fields
 
middle frontal region
 
particular cortical regions
 
preattentive stage
 
prefrontal
 
sound localization
 
stimulation
 
superior temporal region
 
topography