How Does the Brain Represent Speech?

This chapter provides a brief overview of how the brain's auditory system represents speech. Animal experiments have been invaluable in elucidating basic physiological mechanisms of sound encoding, auditory learning, and pattern classification in the mammalian brain. The human auditory nerve contains about 30,000 such nerve fibers, each capable of firing anywhere between zero and several hundred spikes a second. The neural activity patterns are passed on first to the cochlear nuclei, and from there through the superior olivary nuclei to the midbrain, thalamus, and primary auditory cortex. In humans the primary auditory cortex is located around a special wrinkle in the cortical sheet. The chapter describes deeply revealing new work into the linguistic-phonetic representation of speech, obtained using surgical recordings in human brains. It focuses on the systems-level representations of speech perception and on the related topic of temporal prediction, which is at the heart of why we have brains in the first place.