Search Abstracts | Symposia | Slide Sessions | Poster Sessions
Mechanisms for multimodal language processing within the ear
Poster Session C, Thursday, October 1, 10:45 am - 12:45 pm, Wangari Maathai
Stephanie N. Lovich1, Steven J. Eliades1, David M. Kaylie1, Cynthia D. King1, Jennifer M. Groh1; 1Duke University
Language is a multimodal process involving the integration of visual and auditory information. For example, lip reading is beneficial for language acquisition and comprehension in noisy environments. To accurately integrate visual and auditory cues, information about eye movements is also needed – without it, the brain would not be able to correctly link visual and auditory information in space. We have recently reported an eardrum oscillation, time-locked with eye movement onset, and occurring in the absence of outside auditory stimuli, that suggests eye movement information is available as early as the ears (Eye movement-related eardrum oscillation, EMREO; Gruters et al. PNAS 2018; Lovich et al. PNAS 2023). The underlying mechanics of EMREOs in the ear are still unknown. In-ear anatomy generating and/or modulating the EMREO could include the middle ear muscles (MEMs) and/or outer hair cells (OHCs). Given that deficits in these mechanisms have been tied to language dysfunction, it is important to understand their contributions to the EMREO. Here we tested the specific contributions of the two middle ear muscles. We recorded eye movements and eardrum oscillations in awake, behaving rhesus monkeys before and after surgical interventions to disrupt the contributions of one or both MEMs. These surgical procedures mirror procedures performed on human patients for disorders such as otosclerosis and middle-ear myoclonus and involved the transection of the stapedius tendon and/or tensor tympani tendon unilaterally in each monkey. The EMREO was altered but still present after transection of both tendons, indicating the MEMs do not solely generate or control this oscillation and another mechanism, such as the OHCs, is necessary. Additionally, the surgeries indicated that the two MEMs do not modulate the EMREO in the same way. Instead, they apply opposing forces on the EMREO, creating a push-pull system between the muscles to precisely modulate the amplitude of the signal. Understanding how and where the brain integrates visual and auditory/speech information is crucial for patients with middle ear auditory dysfunction or other complex auditory disorders. Children with hyperacusis (dysfunction of the tensor tympani) have a higher likelihood of having difficulty with language processing (Ralli et al. Int Tinnitus J, 2018). Additionally, children with autism and severe language delays have abnormal and delayed stapedial reflexes (Lukose et al. Autism Res, 2013). Finally, people with central auditory processing disorder (CAPD) have difficulty localizing sound and processing language (American Speech-Language-Hearing Association). These together demonstrate that the visual system, auditory system, and eye movements are intrinsically interconnected from the periphery to the brain during language processing.
Topic Areas: Multisensory or Sensorimotor Integration,