Latency of the auditory evoked neuromagnetic field components: Stimulus dependence and insights toward perception

This review will focus on investigations of the auditory evoked neuromagnet ic field component, the M100, detectable in the magnetoencephalogram record ed during presentation of auditory stimuli, approximately 100 milliseconds after stimulus onset. In particular, the dependence of M100 latency on attr ibutes of the stimulus, such as intensity, pitch and timbre will be discuss ed, along with evidence relating M100 latency observations to perceptual fe atures of the stimuli. Comparison with investigation of the analogous elect rical potential component, the N1, will be made. Parametric development of stimuli from pure tones through complex tones to speech elements will be ma de, allowing the influence of spectral pitch, virtual pitch and perceptual categorization to be delineated and suggesting implications for the role of such latency observations in the study of speech processing. The final sec tion will deal with potential clinical applications offered by M100 latency measurements, as objective indices of normal and abnormal cortical process ing.