Presentation

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Voices in my head: activation of auditory cortex during silent reading

Poster D118 in Poster Session D, Wednesday, October 25, 4:45 - 6:30 pm CEST, Espace Vieux-Port

Kathryn Snyder¹, Kiefer Forseth¹, Oscar Woolnough¹, Greg Hickok², Nitin Tandon¹; ¹UTHSC, ²UC Irvine

Reading requires visual word representations to be mapped to both sound and meaning and is an essential life skill that promotes both personal well-being and professional success. However, while dyslexia is the most common learning disability worldwide, its associated pathophysiology remains unclear, and current management strategies consist primarily of behavioral therapy. As such, a better understanding of the neural mechanisms supporting reading would provide important insights into the pathology underlying its disruption and facilitate the development of improved treatment methods. Here, we investigated the role of auditory cortex in silent reading and compared these findings to regions recruited during listening. Data were obtained from 63 patients who underwent invasive electrophysiology (electrodes=8,082). Recordings were acquired during two matched cued-naming tasks using auditory and written descriptions displayed as single words in rapid serial visual presentation. Importantly, the last word in each prompt across both paradigms was crucial to bind semantic concepts. We analyzed broadband gamma activity (BGA; 65-115Hz) to index cognitive engagement of local cortical substrates. Additionally, group-level BGA was estimated using a surface-based mixed effects multilevel analysis. For each written word, visual cortex activity was followed by activation of lateral occipito-temporal cortex and the intraparietal sulcus. Subsequently, activation was seen in the posterior superior temporal gyrus (pSTG; 20.4% BGA, 238ms) and the posterior middle temporal gyrus (pMTG; 29.3% BGA, 266ms), and these regions were also active during listening (pSTG: 128.3% BGA, 161ms; pMTG: 41.3% BGA, 206ms). Activation of pMTG was greatest for the last word for both tasks, which implicates its role in lexical-semantic processing and sentence comprehension. In contrast, activation of pSTG was consistent across each word in the description and preceded pMTG activity, which supports its involvement in orthographic processing. Furthermore, activity from depth electrodes placed along STG in a subset of 37 patients showed a consistent posterior-to-anterior gradient during both listening and silent reading. Electrodes within more anterior regions, including Heschl’s gyrus and the transverse temporal sulcus, showed a sustained activation consistent with entrainment during listening and were quiescent during silent reading. However, electrodes within more posterior regions, including the planum temporale, showed onset-specific, transient activation during listening as well as activation for each word in the description during silent reading. This distinct activity profile further implicates pSTG (primarily the planum temporale) in orthographic decoding and suggests that it may play a critical role in orthographic-to-phonological processing. Altogether, these results contribute a deeper understanding of the spatiotemporal dynamics associated with orthographic processing and the specific functional roles of critical neural substrates. Ultimately, we believe that this work would provide important insights to optimize the design of neural prosthetics for the treatment of reading-related disorders.

Topic Areas: Reading, Speech Perception