Pitch change of a continuous tone activates two distinct processes in human auditory cortex: a study with whole-head magnetometer

• Published in: Electroencephalography and clinical neurophysiology / Evoked potentials section Vol. 96; no. 1; pp. 93 - 96
• Main Authors: Lavikainen, J., Huotilainen, M., Hmoniemi, R.J., Simola, J.T., Näätänen, R.
• Format: Journal Article
• Language: English
• Published: Shannon Elsevier Ireland Ltd 1995; Amsterdam Elsevier
• Subjects: Auditory cortex; Biological and medical sciences; Continuous tone; Ear and associated structures. Auditory pathways and centers. Hearing. Vocal organ. Phonation. Sound production. Echolocation; Fundamental and applied biological sciences. Psychology; Mismatch response; Pitch change; Vertebrates: nervous system and sense organs; Mismatch response; N1; Continuous tone; Auditory cortex; Pitch change; Human; Acoustic stimulus; Magnetoencephalography; Auditory evoked potential; Central nervous system; Electrophysiology; Dipole; Auditory pathway; Pitch(acoustics); Event evoked potential; Brain (vertebrata)
• ISSN: 0168-5597
• DOI: 10.1016/0013-4694(94)00283-Q

Previous studies have shown that a frequency change in a continuous tone elicits an NI type of ERP (event-related potential) component. It remained unclear, however, whether this response is a “genuine” N1 (onset detector response) or the mismatch negativity (MMN), a change-detector type of ERP response, elicited in previous studies by an infrequent change in a sequence of homogeneous stimuli. A further possibility is a nearly perfect overlap of the two types of ERP components. The advent of modern, high-resolution magnetometers has opened a new, powerful way to tackle such component-overlap problems.
Subjects were presented with a continuous tone of 988 Hz which was occasionally increased to 1108 Hz for a period of 100 msec. The magnetic responses to this change consisted of two partially overlapping components with peaks separated by 30 msec. The earlier component was probably generated by neuronal populations of the auditory cortex corresponding to the supratemporal N1, whereas the later one, generated anteriorly and inferiorly to the first, probably reflects a mismatch process causing the magnetic equivalent of the electrical MMN.