Conclusion: The results could indicate that, during phylogeny and human ontogeny, the central nervous system has enhanced the speech activity from any other activity even though other frequencies could be relevant for survival.
Objective: People of all ages can experience alterations of auditory perception that progressively increase with aging. The whole approach to these alterations needs not only peripheral (cochlear) or brainstem studies but also an analysis of the auditory cortex. In fact, auditory evoked fields (AEF) may contribute to the understanding of the neural correlate of sound awareness.
Subjects and methods: The M100 response after pure tone stimulation (five frequencies ranging from 500 to 8000 Hz) was analyzed in a group of nine adult subjects with normal hearing, older than 25 years of age and under 40 years old. Average M100 field intensity was calculated for all magnetoencephalography (MEG) channels in a 60 ms window around the M100 waveform.
Results: The results indicate a more intense cortical response to main speech frequencies (0.5 to 2 kHz) as compared with other frequencies not involved in human conversation.