Identification of a pathway for intelligible speech in the left temporal lobe

Abstract

It has been proposed that the identification of sounds, including species-specific vocalizations, by primates depends on anterior projections from the primary auditory cortex, an auditory pathway analogous to the ventral route proposed for the visual identification of objects. We have identified a similar route in the human for understanding intelligible speech. Using PET imaging to identify separable neural subsystems within the human auditory cortex, we used a variety of speech and speech-like stimuli with equivalent acoustic complexity but varying intelligibility. We have demonstrated that the left superior temporal sulcus responds to the presence of phonetic information, but its anterior part only responds if the stimulus is also intelligible. This novel observation demonstrates a left anterior temporal pathway for speech comprehension.

FMRI reveals brain regions mediating slow prosodic modulations in spoken sentences

“…This finding agrees with several recent neuroimaging studies that also report only minor activation in the inferior frontal cortex during auditory sentence comprehension [Dehaene et al, 1997;Mazoyer et al, 1993;Meyer et al, 2000;Mü ller et al, 1997;Schlosser et al, 1998;Scott et al, 2000]. A selective engagement of left inferior cortex, i.e., Broca's area, is reported by studies that investigated the processing of syntactic information during auditory and written sentence comprehension thereby focussing on syntactic complexity [Caplan et al, 1998[Caplan et al, , 2000.…”

“…This result is in general agreement with recent neuroimaging studies associating auditory sentence comprehension with an involvement of the bilateral STR with the left hemisphere playing a dominant role in right-handed subjects [Kuperberg et al, 2000;Mü ller et al, 1997;Schlosser et al, 1998]. In particular, the (left) anterior STR was shown to play an essential role in processing constituent structures, i.e., general syntactic operations at the sentence-level [Friederici et al, 2000b;Humphries et al, 2001;Meyer et al, 2000;Scott et al, 2000]. In line with these earlier studies, the present study reveals greater activation in the anterior and mid STR relative to posterior STR regions during sentence processing (cf.…”

Volumetric vs. surface-based alignment for localization of auditory cortex activation

“…Nevertheless, these results support the view that areas in the left temporal plane are involved in the analysis of acoustic properties of sounds and more ventral areas in the upper STS are involved in phonetic or categorical perception (Binder et al, 2000;Scott et al, 2000;Liebenthal et al, 2003). The involvement of the dorsal bank of left STS in speech perception is also supported by physiological studies in non-human primates, suggesting auditory sensitivity in this region but not in the ventral bank of STS (Baylis et al, 1987;Seltzer and Pandya, 1994;Poremba et al, 2003).…”

Lexical Information Drives Perceptual Learning of Distorted Speech: Evidence From the Comprehension of Noise-Vocoded Sentences.

“…Although it is well-known that the intelligibility of noise-vocoded speech (as for other distortions) changes with practice (see, e.g., Giraud et al, 2004;Rosen et al, 1999;Scott et al, 2000), to our knowledge, the rate and extent of these changes in intelligibility have not been quantified. This experiment also sets out methods that will be used in subsequent experiments.…”