Somatosensory Cross-Modal Reorganization in Adults With Age-Related, Early-Stage Hearing Loss

Abstract

Under conditions of profound sensory deprivation, the brain has the propensity to reorganize. For example, intact sensory modalities often recruit deficient modalities’ cortices for neural processing. This process is known as cross-modal reorganization and has been shown in congenitally and profoundly deaf patients. However, much less is known about cross-modal cortical reorganization in persons with less severe cases of age-related hearing loss (ARHL), even though such cases are far more common. Thus, we investigated cross-modal reorganization between the auditory and somatosensory modalities in older adults with normal hearing (NH) and mild-moderate ARHL in response to vibrotactile stimulation using high density electroencephalography (EEG). Results showed activation of the somatosensory cortices in adults with NH as well as those with hearing loss (HL). However, adults with mild-moderate ARHL also showed robust activation of auditory cortical regions in response to somatosensory stimulation. Neurophysiologic data exhibited significant correlations with speech perception in noise outcomes suggesting that the degree of cross-modal reorganization may be associated with functional performance. Our study presents the first evidence of somatosensory cross-modal reorganization of the auditory cortex in adults with early-stage, mild-moderate ARHL. Our findings suggest that even mild levels of ARHL associated with communication difficulty result in fundamental cortical changes.

Cortical Neuroplasticity and Cognitive Function in Early-Stage, Mild-Moderate Hearing Loss: Evidence of Neurocognitive Benefit From Hearing Aid Use

“…Earlier CVEP latencies have been reported in deaf adults and adults with ARHL in previous EEG studies, and are considered an index of visual cross-modal re-organization (Neville and Lawson, 1987;Finney et al, 2003;Fine et al, 2005;Doucet et al, 2006;Buckley and Tobey, 2011;Sandmann et al, 2012;Hauthal et al, 2013;Campbell and Sharma, 2014), where earlier latencies reflect increased synaptic strength and connectivity (Driver and Spence, 2004). Our observations of more extensive visual cross-modal re-organization in the right temporal ROI is also similar to findings from Cardon and Sharma (2018), where there was more extensive cross-modal recruitment of right auditory cortex by the somatosensory modality in adults with ARHL compared to NH controls. Because right auditory cortex has been shown to be more susceptible to atrophy in ARHL (Lin et al, 2014), the deprived auditory cortex may be recruited or 're-purposed' for visual or somatosensory processing.…”

“…CDRs are depicted by a graded color scale (F-statistic) indicating the statistical likelihood of cortical activity in each region. This described protocol has been used in our laboratory to observe changes in visual crossmodal plasticity in adults and children with hearing loss at the single-subject and group level Sharma, 2014, 2016;Sharma et al, 2015Sharma et al, , 2016Cardon and Sharma, 2018).…”

“…For example, adults with mild-moderate ARHL exhibit more extensive recruitment of auditory cortex during visual motion and face processing tasks relative to NH subjects (Campbell and Sharma, 2014;Stropahl and Debener, 2017). Similarly, vibrotactile stimulation in adults with ARHL elicits more extensive cross-modal neural activity in the auditory cortex (Cardon and Sharma, 2018). Both visual and somatosensory crossmodal re-organization are associated with poorer auditory speech perception outcomes (Campbell and Sharma, 2014;Cardon and Sharma, 2018), but the extent to which these neuroplastic changes influence cognitive outcomes has not been investigated.…”

“…Similarly, vibrotactile stimulation in adults with ARHL elicits more extensive cross-modal neural activity in the auditory cortex (Cardon and Sharma, 2018). Both visual and somatosensory crossmodal re-organization are associated with poorer auditory speech perception outcomes (Campbell and Sharma, 2014;Cardon and Sharma, 2018), but the extent to which these neuroplastic changes influence cognitive outcomes has not been investigated.…”

From Detection to Intervention Psychological Aspects of Online Hearing Rehabilitation

“…Therefore, hearing problems can have a serious negative impact on those affected. It is very common to perceive hearing problems, and hearing problems can be thought of as a continuous variable where most people, at least in some situations, have difficulties (Cardon & Sharma, 2018). For example, people with a clinically established normal hearing ability can still have a hard time communicating in places like noisy restaurants (Ruggles, Bharadwaj, & Shinn-Cunningham, 2011).…”