Neural Substrates of Phonemic Perception

Abstract

The temporal lobe in the left hemisphere has long been implicated in the perception of speech sounds. Little is known, however, regarding the specific function of different temporal regions in the analysis of the speech signal. Here we show that an area extending along the left middle and anterior superior temporal sulcus (STS) is more responsive to familiar consonant-vowel syllables during an auditory discrimination task than to comparably complex auditory patterns that cannot be associated with learned phonemic categories. In contrast, areas in the dorsal superior temporal gyrus bilaterally, closer to primary auditory cortex, are activated to the same extent by the phonemic and nonphonemic sounds. Thus, the left middle/anterior STS appears to play a role in phonemic perception. It may represent an intermediate stage of processing in a functional pathway linking areas in the bilateral dorsal superior temporal gyrus, presumably involved in the analysis of physical features of speech and other complex non-speech sounds, to areas in the left anterior STS and middle temporal gyrus that are engaged in higher-level linguistic processes.

Individual differences in the acquisition of second language phonology

“…Thus, the above dissociations that we find in performance with the two stimulus types may be due not only to the fact that one is speech and the other not, but they may also be due to stimulus complexity. In support of the idea that different learning mechanisms exist for speech and non-speech sounds, there exists evidence from other studies for speech-specific neural mechanisms when stimulus complexity is controlled (Liebenthal, Binder, Spitzer, Possing, & Medler, 2005;Scott, Blank, Rosen, & Wise, 2000;Scott, Rosen, Lang, & Wise, 2006), or when the same stimuli are first perceived as nonspeech and then later as speech (Dehaene-Lambertz et al, 2005;Dufor, Serniclaes, Sprenger-Charolles, & Démonet, 2007). More generally, it is likely that the neural mechanisms underlying the processing of abstract, linguistically relevant properties versus of the underlying acoustic characteristics of stimuli interact in a complex and non-exclusive manner, and that they depend on linguistic experience as well as on neural top-down processing mechanisms which interact with afferent pathways which carry stimulus information (Zatorre & Gandour, 2007).…”

Attentional and linguistic interactions in speech perception

“…Several recent studies comparing phonetic sounds to acoustically matched nonphonetic sounds (Dehaene-Lambertz et al, 2005;Liebenthal et al, 2005;Mottonen et al, 2006) or to noise (Binder et al, 2000;Rimol et al, 2005) have shown activation specifically in this brain region. Two factors might explain these discordant findings.…”

Auditory Cortex Encodes the Perceptual Interpretation of Ambiguous Sound

“…3a), including auditory areas in the superior temporal cortex (Heschl's gyrus), multiple regions in the planum temporale (PT), superior temporal gyrus and sulcus (STG and STS, respectively), as well as middle temporal gyrus, insula cortex, inferior parietal cortex, inferior frontal cortex, and supramarginal gyrus (Davis and Johnsrude, 2003;Liebenthal et al, 2005;Hickok and Poeppel, 2007;Desai et al, 2008). A univariate comparison between trials perceptually classified as /aba/ and those classified as /ada/ did not yield significant differences in activation (q ϭ 0.05, corrected for multiple comparisons with false discovery rate).…”

“…According to popular models of auditory processing, representations become more abstract with hierarchical distance to the primary auditory cortex (A1) along two (what/where) pathways (Scott and Johnsrude, 2003;Liebenthal et al, 2005;Rauschecker and Scott, 2009). In humans, the regions adjacent to the Heschl's gyrus, which we refer to as early auditory cortex, are supposedly restricted to the analysis of physical features and the acoustic structure of sounds.…”