ABSTRACT
An understanding of the biological foundations of speech perception demands a corresponding appreciation of the neural encoding of complex sounds. Our interests span a range of topics in these interrelated fields of auditory perception and neurophysiology. Among them are the encoding of complex sounds in auditory midbrain, thalamus, and cortex. The evoked response approach permits measurement, with precise timing, of phasic and tonic aspects of the encoding of such sounds. Of particular interest is the aggregate neural response to speech. Many of these responses include both transient and sustained components, much like a speech signal itself. Inasmuch as it may be an oversimplification to equate features of speech, such as consonants and vowels, with transient and sustained evoked responses, there are certain parallels. Just as perception of consonant sounds is much more vulnerable to disruption with background noise, the analogous neural transient response is degraded by noise. Likewise, phase-locked responses are hallmarks of subcortical auditory pathways and may be measured in scalp recordings from humans and direct intracranial recordings in an animal model. Temporal and spectral analyses of these responses have been shown to directly reflect some of the analogous characteristics of the corresponding stimuli, for example the fundamental frequency and some harmonic structures of a vowel.
