Extinction of auditory stimuli in hemineglect: space versus ear.
Poster Presentation

Lucas Spierer
Division de Neuropsychologie, CHUV, Faculté de Biologie et de Médecine, Université de Lausanne, Switzerland

Stephanie Clarke
Division de Neuropsychologie, CHUV, Faculté de Biologie et de Médecine, Université de Lausanne, Switzerland

     Abstract ID Number: 88
     Full text: Not available
     Last modified: March 21, 2005

Abstract
Unilateral extinction of auditory stimuli, a key feature of the neglect syndrome, was investigated in 9 patients with right (3) or bilateral (6) hemispheric lesions using a verbal dichotic condition, in which each ear received simultaneously one word, and a interaural-time-difference (ITD) diotic condition, in which both ears received both words spatially separated by means of ITD. Additional investigations included sound localisation, visuo-spatial attention and general cognitive status.

Three patients presented a significant asymmetry in both diotic and dichotic tasks, associated or not with deficits in sound localisation. One other patient had normal performance in all three.

Two patients presented a significant asymmetry in the dichotic test, due to a significant decrease of left-ear reporting while right-ear reporting was normal; no asymmetry was found in diotic listening.

Three other patients presented a significant asymmetry in the diotic test due to a significant decrease of left-hemispace reporting. No asymmetry was found in dichotic listening, although there was a significant decrease of reporting from either ear.

The double dissociation between asymmetric extinction in the dichotic vs diotic tasks suggests that different mechanisms govern the suppression of information from one ear and the extinction that operates at the level spatial representations.