Schedule of Events | Symposia

The sound of silence: Intracranial recordings of covert and overt speech

Poster Session E - Monday, March 31, 2025, 2:30 – 4:30 pm EDT, Back Bay Ballroom/Republic Ballroom

Taisha Donnelly¹ (taisha.donnelly@univ-grenoble-alpes.fr), Ioana Mîndruță^2,3, Andrei Barborica⁴, Andrei-Alexandru Vasiliu⁴, Jean-Baptiste Eichenlaub¹, Irina Oane^2,3, Monica Baciu¹, Hélène Lœvenbruck¹; ¹Univ. Grenoble Alpes, Univ. Savoie Mont Blanc, CNRS, LPNC, Grenoble, France, ²Emergency University Hospital Bucharest, Bucharest, Romania, ³Carol Davila University of Medicine and Pharmacy Bucharest, Bucharest, Romania, ⁴University of Bucharest, Bucharest, Romania

Inner speech, or verbal thought, is commonly used for planning, reasoning, and self-regulation. It can be considered a form of motor simulation, wherein multisensory predictions from speech motor plans generate the sensory content of an inner voice. The same mechanisms may support motor control in overt speech through internal monitoring prior to motor execution. To investigate shared recruitment of motor planning and sensory prediction processes across overt and covert speech modes, we compared the neural dynamics of picture naming across each mode, evaluating the high-gamma responses (80-150Hz) using intracranial EEG. Our final dataset included seven patients, who participated in this study while explored with stereo-EEG during presurgical evaluations for focal drug-resistant epilepsy. Group-level analyses revealed peaks in speech motor planning regions around 300-500ms post-stimulus for both modes, with an additional primary motor cortex peak (~1000ms) exclusive to overt speech, indicating motor execution. Somatosensory regions showed activity around 500ms in both conditions, with a second peak after 1000ms in overt speech. Late auditory activity (>1000ms) occurred only in overt speech. However, early auditory responses (~500ms) were observed in overt speech for two patients and in covert speech for one patient, which may reflect the subjective experience of an inner voice. Overall, the neural dynamics of covert and overt speech support the predictive control hypothesis, highlighting common recruitment of speech motor planning regions and some evidence for sensory predictions before motor execution. This research lays the foundation for advancing speech neuroprosthetics and treating inner speech dysfunctions, such as auditory verbal hallucinations.

Topic Area: LANGUAGE: Other