Rapid change of tonotopic maps in the human auditory cortex during pitch discrimination.
OBJECTIVE
To study early cognitive processes and hemispheric differences in the primary auditory cortex during selective attention.


METHODS
We measured auditory evoked magnetic fields (AEFs) to 400 and 4000 Hz tone pips that were randomly presented at the right or left ear. Subjects paid attention to target stimuli during pitch (high or low) or laterality (left or right) discrimination tasks. In the control session, 400 or 4000 Hz tone alone was presented at the left or right ear. We calculated the location and strength of N100m dipole for 400 and 4000 Hz tones, based on the AEFs obtained from the hemisphere contralateral to the stimulated ear.


RESULTS
N100m amplitude increased in both hemispheres in pitch or laterality discriminating conditions. N100m latency also shortened during selective attention. The N100m dipole distance between 400 and 4000 Hz tones was enlarged, especially in the right auditory cortex during pitch discrimination task, but was unchanged during the laterality discrimination task.


CONCLUSIONS
We conclude that these dynamic changes in the N100m dipole reflect short-term plastic changes in the primary auditory cortex, supporting early selection models.


CONCLUSIONS
This work is the first to disclose short-term plastic changes during pitch discrimination in the human auditory cortex based on the analysis of magnetoencephalography.
Ozaki
Isamu
I
Department of Physical Therapy, Faculty of Health Science, Aomori University of Health and Welfare, 58-1 Mase, Hamadate, Aomori 030-8505, Japan. isamu@auhw.ac.jp
Jin
Chun Yu
CY
Suzuki
Yasumi
Y
Baba
Masayuki
M
Matsunaga
Muneo
M
Hashimoto
Isao
I
D000161:Acoustic Stimulation / Q000379:methods; D000328:Adult; D001303:Auditory Cortex / Q000502:physiology*; D001931:Brain Mapping; D004292:Dominance, Cerebral; D005072:Evoked Potentials, Auditory; D006801:Humans; D015225:Magnetoencephalography; D009473:Neuronal Plasticity; D010897:Pitch Discrimination / Q000502:physiology*