Numeric aspects in pitch identification: an fMRI study

BACKGROUND: Pitch identification had yielded unique response patterns compared to other auditory skills. Selecting one out of numerous pitches distinguished this task from detecting a pitch ascent. Encoding of numerous stimuli had activated the intraparietal sulcus in the visual domain. Therefore, we hypothesized that numerosity encoding during pitch identification activates the intraparietal sulcus as well. METHODS: To assess pitch identification, the participants had to recognize a single pitch from a set of four possible pitches in each trial. Functional magnetic resonance imaging (fMRI) disentangled neural activation during this four-pitch-choice task from activation during pitch contour perception, tone localization, and pitch discrimination. RESULTS: Pitch identification induced bilateral activation in the intraparietal sulcus compared to pitch discrimination. Correct responses in pitch identification correlated with activation in the left intraparietal sulcus. Pitch contour perception activated the superior temporal gyrus conceivably due to the larger range of presented tones. The differentiation between pitch identification and tone localization failed. Activation in an ACC-hippocampus network distinguished pitch discrimination from pitch identification. CONCLUSION: Pitch identification is distinguishable from pitch discrimination on the base of activation in the IPS. IPS activity during pitch identification may be the auditory counterpart of numerosity encoding in the visual domain.