Affiliations: Department of Neurology, Medical School of Hannover,
30623 Hannover, Germany
Note: [] Corresponding author Dr. S. Johannes, Department of Neurology,
Medical School of Hannover, 30623 Hannover, Germany. Tel.: +49 511 5322023, +49
511 5323578; Fax: +49 511 5323115; E-mail: johannes@vm.mhrz.mh-hannover.de.
Abstract: In the auditory modality, there has been a considerable debate about
some aspects of cortical disorders, especially about auditory forms of agnosia.
Agnosia refers to an impaired comprehension of sensory information in the
absence of deficits in primary sensory processes. In the non-verbal domain,
sound agnosia and amusia have been reported but are frequently accompanied by
language deficits whereas pure deficits are rare. Absolute pitch and musicians'
musical abilities have been associated with left hemispheric functions. We
report the case of a right handed sound engineer with the absolute pitch who
developed sound agnosia and amusia in the absence of verbal deficits after a
right perisylvian stroke. His disabilities were assessed with the Seashore Test
of Musical Functions, the tests of Wertheim and Botez (Wertheim and Botez, Brain 84, 1961, 19-30) and by event-related potentials (ERP) recorded
in a modified 'oddball paradigm'. Auditory ERP revealed a dissociation between
the amplitudes of the P3a and P3b subcomponents with the P3b being reduced in
amplitude while the P3a was undisturbed. This is interpreted as reflecting
disturbances in target detection processes as indexed by the P3b. The findings
that contradict some aspects of current knowledge about left/right hemispheric
specialization in musical processing are discussed and related to the
literature concerning cortical auditory disorders.
