Speech categories are represented hierarchically along the auditory cortex

Evidence

Categories for more complex stimuli, such as speech sounds and vocalizations, can be found in the lateral belt (Chang et al. 2010 ; Steinschneider et al. 2011 ; Tsunada et al. 2011 ; Steinschneider 2013 ). For example, AL neurons respond categorically, and in a manner consistent with listeners’ behavioral reports, to morphed versions of two speech sounds (“bad” and “dad”). AL neurons also respond categorically to species-specific vocalizations; however, the degree to which AL (and listeners) can categorize these vocalizations is constrained by the vocalizations’ acoustic variability (Christison-Lagay et al. 2014 ). … In humans, the superior temporal gyrus is categorically and hierarchically organized by speech sounds (Binder et al. 2000 ; Chang et al. 2010 ; Leaver and Rauschecker 2010 ): phoneme categories are found in the middle aspect; word categories in the anterior-superior aspect; and phrases in the most anterior aspect (DeWitt and Rauschecker 2012 ; Rauschecker 2012 ). — Dijk, Pim van, Physiology, Psychoacoustics and…, 4896

Categorization

• DEFINE: This passage maps phoneme, word, and phrase representations onto specific anatomical positions in the superior temporal gyrus — a useful spatial catalog of speech-category processing.