Involvement of Auditory Dorsal Stream in Processing of Spectrally Degraded Speech Examined with iEEG
Poster No:
1042
Submission Type:
Abstract Submission
Authors:
Kirill Nourski1, Mitchell Steinschneider1, Ariane Rhone1, Joel Berger1, Emily Dappen1, Hiroto Kawasaki1, Matthew Howard1
Institutions:
1The University of Iowa, Iowa City, IA
First Author:
Co-Author(s):
Introduction:
Cochlear implants (CIs) are the treatment choice for severe to profound hearing loss. Despite the tremendous progress in CI technology, including hardware and processing strategies, there remains a considerable variability in speech perception outcomes following implantation (Geers, 2006; Pisoni et al., 2017; Carlyon and Goehring, 2021). The function and plasticity of central auditory pathways are major contributing factors to this variability (Moberly et al., 2016; Glennon et al., 2020; Pavani & Bottari, 2022). Assessing auditory processing at the cortical level in CI users is methodologically difficult. However, spectrally degraded sounds presented to normal-hearing individuals can approximate the input to the central auditory system provided by the CI (Shannon et al., 1995). This study used intracranial electroencephalography (iEEG) to investigate cortical processing of spectrally degraded speech.
Methods:
Participants were 15 adult neurosurgical epilepsy patients. Stimuli were utterances /aba/ and /ada/, spectrally degraded using a noise vocoder (1-4 bands) or presented without vocoding (Fig. 1a; Nourski et al., 2019). The stimuli were presented in a two-alternative forced choice task. Cortical activity was recorded using depth and subdural iEEG electrodes (2051 contacts). Electrode coverage included Heschl's gyrus (HG), superior temporal gyrus (STG), dorsal and ventral auditory-related areas, prefrontal and sensorimotor cortex. Analysis focused on high gamma (70-150 Hz) power augmentation and alpha (8-14 Hz) suppression, measured at 250-500 and 500-750 ms after stimulus onset, respectively.
·Experimental stimuli and task performance.
Results:
Chance task performance occurred with 1-2 spectral bands and was near-ceiling for clear stimuli (Fig. 1b). Performance was variable with 3-4 bands, permitting segregation of good from poor performers Fig. 1c). There was no relationship between task performance and participants' demographic, audiometric, neuropsychological, or clinical profiles. Several patterns were identified based on high gamma response magnitude and differences between stimulus conditions (Fig. 2a). Within HG, responses were typically strong to all stimuli, while more diverse patterns emerged on the lateral STG. Good performers typically had strong responses to all stimuli along the dorsal auditory processing stream, including posterior STG, supramarginal, and precentral gyrus (Fig. 2b). Additional recruitment of the dorsal stream for the difficult (vocoded) stimuli manifested as vocoded-preferred responses. In poor performers, clear-specific responses in the dorsal stream were more common, suggesting that within the dorsal stream, vocoded stimuli were not processed as speech. In contrast, poor performers engaged the ventral stream (posterior middle temporal gyrus, MTGP) to a greater extent than good performers. Patterns of alpha suppression were generally less diverse than high gamma augmentation; differences between good and poor performers paralleled those seen in high gamma responses.
·High gamma response patterns in participants who exhibited good and poor task performance.
Conclusions:
Responses to noise-vocoded speech provide insights into potential factors underlying CI outcome variability. The results emphasize differences between good and poor performers in the balance of neural processing along the dorsal and ventral stream, identify specific cortical regions that may have diagnostic and prognostic utility, and suggest potential targets for neuromodulation-based CI rehabilitation strategies.
Language:
Speech Perception 1
Perception, Attention and Motor Behavior:
Perception: Auditory/ Vestibular 2
Keywords:
Other - alpha suppression; auditory cortex; cochlear implants; high gamma; noise vocoder; task performance; variability
1|2Indicates the priority used for review
Provide references using author date format
Geers, .AE. (2006), ‘Factors influencing spoken language outcomes in children following early cochlear implantation’, Advances in Otorhinolaryngology, vol. 64, pp. 50-65.
Glennon, E., Svirsky, M.A., Froemke, R.C. (2020), ‘Auditory cortical plasticity in cochlear implant users’ Current Opinion in Neurobiology, vol. 60, pp. 108-114.
Moberly, A.C., Bates, C., Harris, M.S., Pisoni, D.B. (2016), ‘The Enigma of Poor Performance by Adults With Cochlear Implants’, Otology and Neurotology, vol. 37, no. 10, pp. 1522-1528.
Nourski, K.V., Steinschneider, M., Rhone, A.E., Kovach, C.K., Kawasaki, H., Howard, M.A. 3rd. (2019), ‘Differential responses to spectrally degraded speech within human auditory cortex: An intracranial electrophysiology study’, Hearing Research, vol. 371, pp. 53-65.
Pavani, F., Bottari, D. (2022), ‘Neuroplasticity following cochlear implants’, Handbook of Clinical Neurology, vol. 187, pp. 89-108.
Pisoni, D.B., Kronenberger, W.G., Harris, M.S., Moberly, A.C. (2018), ‘Three challenges for future research on cochlear implants’, World Journal of Otorhinolaryngology - Head and Neck Surgery, vol. 3, no. 4, pp. 240-254.
Shannon, R.V., Zeng, F.G., Kamath, V., Wygonski, J., Ekelid, M. (1995), ‘Speech recognition with primarily temporal cues’, Science vol. 270, no. 5234, pp. 303-304.