Processing specificity for human voice stimuli: electrophysiological evidence.

Recent neuroimaging studies have provided evidence for localized perceptual specificity in the processing of human voice stimuli, paralleling the specificity for human faces. This study attempted to delineate the perceptual features of human voices yielding selective processing, and to characterize its time-course. Electrophysiological recordings revealed a positive potential peaking at 320 ms post-stimulus onset, in response to sung tones compared with fundamental-frequency-matched instrumental tones, when both categories were distracters in an oddball task. This voice-specific response (VSR) evoked under conditions different from those yielding positivity at that latency in other contexts, indicates the overriding salience of voice stimuli, possibly reflecting the operation of a gating system directing voice stimuli to be processed differently from other acoustic stimuli.

Absolute pitch--electrophysiological evidence.

People who have the ability to label or to produce notes without any reference are considered to possess Absolute Pitch (AP). Others, who need a reference in order to identify the notes, possess Relative Pitch (RP). The AP ability is assumed to reflect a unique, language-like representation of non-lexical musical notes in memory. The purpose of this study was to examine this assumption by comparing Event Related Potentials (ERP) of musicians with and without AP, to lexical and non-lexical representation of musical material. Subjects were eighteen young adult musicians. Seven were AP and eleven RP. Auditory stimuli, presented through earphones, were piano notes (non-lexical) or a voice saying the note's name (lexical). Visual stimuli, presented on a computer display were note symbols (non-lexical) or letters (lexical). Subjects performed a number of tasks, combining the two modalities (visual and auditory) and stimulus types (lexical and non-lexical), and reaction times (RT), performance accuracy and evoked potentials were recorded. The tasks forced the subjects to transfer mental representations of musical material from one mode to another. Our most important findings were the differences, between groups, in the scalp distribution of P300 amplitudes. We conclude that absolute pitch possessors use the same internal language as relative pitch possessors, when possible, but the distribution of the underlying brain activity is different between AP and RP subjects.