Gestalt recognition in a virtual melody experiment

The pitch of a harmonic complex tone corresponds to its fundamental frequency (f0). Interestingly, this sensation does not depend on the physical presence of f0. The phenomenon, commonly referred to as virtual pitch [1], has often been compared to the perception of visual illusory contours. It is contrasted by the perception of spectral pitches, elicited by a tone's physically present harmonics. While, in principle, each human subject and even higher vertebrates [2,3,4] are able to perceive missing fundamentals, the predominance of one type of pitch perception over the other (spectral vs. virtual) has been shown to depend on the spectral content of the stimulus as well as on the subject’s musical experience [5]. Experiments using ambiguous two-tone sequences revealed that “spectral listeners” can be trained to switch to the virtual mode of pitch perception. In contrast, for “virtual listeners”, a reversed training was without success [6]. This finding indicates a hierarchical organization of the two processes, the spectral mode being the basis for higher level virtual pitch formation. Thus, the aim of the present study was to investigate the role of the auditory cortex for both modes of pitch perception. In the present experiment, auditory evoked fields (AEFs) in the low frequency range (0-20Hz, slowAEF, N1m component with latency of about 100ms after stimulus onset) and in the gamma frequency range (24-48Hz [8], with its maximum at latencies of about 30-80ms, c.f. figure 4) elicited by a sequence of complex tones with their fundamental frequencies missing were investigated. N1m and the gamma band responses were recorded from the left and the right hemisphere of the test subjects, when they: a) perceived the "foreground" spectral melody and b) when they recognized the "hidden" virtual melody after successful training 2 Methods