Evidence for a Spoken Word Lexicon in the Auditory Ventral Stream

Abstract

The existence of a neural representation for whole words (i.e., a lexicon) is a common feature of many models of speech processing. Prior studies have provided evidence for a visual lexicon containing representations of whole written words in an area of the ventral visual stream known as the “Visual Word Form Area” (VWFA). Similar experimental support for an auditory lexicon containing representations of spoken words has yet to be shown. Using fMRI rapid adaptation techniques, we provide evidence for an auditory lexicon in the “Auditory Word Form Area” (AWFA) in the human left anterior superior temporal gyrus that contains representations highly selective for individual spoken words. Furthermore, we show that familiarization with novel auditory words sharpens the selectivity of their representations in the AWFA. These findings reveal strong parallels in how the brain represents written and spoken words, showing convergent processing strategies across modalities in the visual and auditory ventral streams.

Regional homogeneity as a marker of sensory cortex dysmaturity in preterm infants

“…We then iteratively threshold-ed the following map to generate ROIs of ∼20 voxels each. Of note, 20 voxels (∼540mm 3 ) was chosen to be similar to ROI volumes used in adult fMRI studies 80 , 81 , 82 , 83 which can range from ∼200 to 500mm 3 . Although ROIs containing a larger number of voxels could be used, we believe this would limit the interpretability of our results given the significantly smaller brain volumes of infants compared to adults.…”

Neural manifolds carry reactivation of phonetic representations during semantic processing

“…At the semantic level, the anterior superior temporal gyrus (aSTG), as a part of the clear anatomo-functional separation from the middle STG (Scott, 2000;Visser and Lambon Ralph, 2011;Chang et al, 2015;Zhang et al, 2021;Damera et al, 2023). In functional MRI (fMRI) data, neural activity recorded through incrementally higher cognitive brain regions correlates with increasingly deeper layers in large language models (Caucheteux et al, 2022).…”

“…Fine-grained electrocorticography (ECoG) recordings from the middle and posterior STG reveal that phonetic features are encoded without strict spatial segregation, but rather via mixed interleaved representations (Hamilton et al, 2021). At the semantic level, the anterior superior temporal gyrus (aSTG), as a part of the ATL, responds more specifically to semantic decisions from heard speech, without a clear anatomo-functional separation from the middle STG (Scott, 2000; Visser and Lambon Ralph, 2011; Chang et al, 2015; Zhang et al, 2021; Damera et al, 2023). In functional MRI (fMRI) data, neural activity recorded through incrementally higher cognitive brain regions correlates with increasingly deeper layers in large language models (Caucheteux et al, 2022).…”