Prefrontal cortex supports speech perception in listeners with cochlear implants

Abstract

Cochlear implants are neuroprosthetic devices that can restore hearing in individuals with severe to profound hearing loss by electrically stimulating the auditory nerve. Because of physical limitations on the precision of this stimulation, the acoustic information delivered by a cochlear implant does not convey the same level of spectral detail as that conveyed by normal hearing. As a result, speech understanding in listeners with cochlear implants is typically poorer and more effortful than in listeners with normal hearing. The brain networks supporting speech understanding in listeners with cochlear implants are not well understood, partly due to difficulties obtaining functional neuroimaging data in this population. In the current study, we assessed the brain regions supporting spoken word understanding in adult listeners with right unilateral cochlear implants (n=20) and matched controls (n=18) using high-density diffuse optical tomography (HD-DOT), a quiet and non-invasive imaging modality with spatial resolution comparable to that of functional MRI. We found that while listening to spoken words in quiet, listeners with cochlear implants showed greater activity in the left dorsolateral prefrontal cortex, overlapping with functionally-defined domain-general processing seen in a spatial working memory task. These results suggest that listeners with cochlear implants require greater cognitive processing during speech understanding than listeners with normal hearing, supported by compensatory recruitment in the left dorsolateral prefrontal cortex.

Brightening the Study of Listening Effort with Functional Near-Infrared Spectroscopy: A Scoping Review

“…105,106 More recently, HD-DOT has been explored as a means to increase spatial resolution of imaging in cochlear implant users. 107 In contrast, relatively few studies have investigated auditory perception in hearing aid users with fNIRS. Two studies to be discussed later tested adult and children who use hearing aids in listening effort tasks, but other fNIRS work in hearing aid users is currently limited.…”

“…31 As the density of commercially available fNIRS systems increases, more opportunities to image a larger portion of the cortex arise. For example, a preprint by Sherafati et al 107 has used HD-DOT to compare cortical activations in cochlear implant users and normal-hearing adults, allowing high-resolution imaging across a wider scalp area at varying depths of cortical penetration.…”