Cortical Activity at Rest Predicts Cochlear Implantation Outcome

Abstract

The functional status of central neural pathways, in particular their susceptibility to plasticity and functional reorganization, may influence speech performance of deaf cochlear implant users. In this paper, we sought to determine how brain metabolic activity measured before implantation relates to cochlear implantation outcome, that is, speech perception. In 22 prelingually deaf children between 1 and 11 years, we correlated preoperative glucose metabolism as measured by F-18 fluorodeoxyglucose positron emission tomography with individual speech perception performance assessed 3 years after implantation, while factoring out the confounding effect of age at implantation. Whereas age at implantation was positively correlated with increased activity in the right superior temporal gyrus, speech scores were selectively associated with enhanced metabolic activity in the left prefrontal cortex and decreased metabolic activity in right Heschl's gyrus and in the posterior superior temporal sulcus. These results reinforce the notion that implantation should be performed as early as possible to prevent cross-modal takeover of auditory regions and suggest that rehabilitation strategies may be more efficient if they capitalize on general cognitive functions instead of only targeting specialized circuits dedicated to auditory and audiovisual pattern recognition.

Lateralization of Interimplant Timing and Level Differences in Children Who Use Bilateral Cochlear Implants

“…Further downstream, cochlear inactivation can lead to atrophic changes (such as reductions of neurons' soma areas or synaptic densities) in the SOC, the nucleus of the lateral lemniscus and the central nucleus of the inferior colliculus (Nishiyama et al 2000;Shepherd and Hardie 2001). Imaging studies have shown that, without activity from lower centres of the auditory system, the auditory cortex undergoes crossmodal plasticity, whereby other sensory modalities (particularly vision) take-over areas of the cortex normally specialized for hearing (reviewed in Lee et al 2001;Lee et al 2007). Studies using the deaf white cat as a model for congenital deafness have indicted that these animals have decreased spiral ganglion cell density, decreased cell size in the MSO, and decreased number and size of synaptic terminals in the MSO (Schwartz and Higa 1982).…”

“…Previous literature has suggested that electrical stimulation delivered from within the cochlea may help to prevent some of the degeneration normally caused by profound SNHL (Leake et al 2008;Vollmer et al 2005). For example, in order to diminish cross-modal takeover, children are often provided with cochlear implants as early as possible; so as to best promote speech perception performance (Lee et al 2007). Moreover, evoked potential studies have shown that the deaf and immature auditory brainstem retains the ability to change in response to prolonged stimulation from a single cochlear implant .…”

“…This ability does not diminish with age at implantation/duration of deafness, suggesting that the auditory brainstem remains plastic in the absence of stimulation during development 2006;Gordon et al 2008;Thai-Van et al 2007). Therefore, while congenital deafness results in degeneration and rearrangement along the auditory system, provision of a single cochlear implant may help to prevent further degradation and also results in some degree of maturation in the auditory brainstem 2006;Gordon et al 2008;Leake et al 2008;Lee et al 2007; Thai- Van et al 2007;Vollmer et al 2005). …”

Bilateral reorganization of posterior temporal cortices in post‐lingual deafness and its relation to cochlear implant outcome

“…The right posterior superior temporal gyrus/supramarginal gyrus (PSTG/SMG) undergoes a profound reorganization during deafness that is manifest in a hypermetabolism at rest [Giraud and Lee, 2007;Lee et al, 2007a], and in abnormal activation levels during visual speech tasks (rhyming and lip-reading tasks) [Lazard et al, 2010b;Lee et al, 2007b]. We previously argued that the involvement of this region in visually driven speech processing may be maladaptive, as it predicts poor phonological scores in deaf subjects and poor auditory speech perception after receiving a CI [Lazard et al, 2010b].…”

Factors Contributing to Speech Performance in Elderly Cochlear Implanted Patients: An FDG-PET Study: A Preliminary Study

“…The reason why age has an important prognostic value is associated with brain plasticity; that is, age itself independently is not a major determinant, but rather, prelingual auditory deprivation, which causes brain plasticity, is. A low metabolic rate in the temporal cortices before CI is related to a more favorable speech perception outcome after CI [3][4][5][6] . There is controversy regarding functional reorganization in postlingual deaf adults [7] because the adult brain has already completed functional organization.…”