Somatosensory processing in deaf and deafblind individuals: How does the brain adapt as a function of sensory and linguistic experience? A critical review

Abstract

How do deaf and deafblind individuals process touch? This question offers a unique model to understand the prospects and constraints of neural plasticity. Our brain constantly receives and processes signals from the environment and combines them into the most reliable information content. The nervous system adapts its functional and structural organization according to the input, and perceptual processing develops as a function of individual experience. However, there are still many unresolved questions regarding the deciding factors for these changes in deaf and deafblind individuals, and so far, findings are not consistent. To date, most studies have not taken the sensory and linguistic experiences of the included participants into account. As a result, the impact of sensory deprivation vs. language experience on somatosensory processing remains inconclusive. Even less is known about the impact of deafblindness on brain development. The resulting neural adaptations could be even more substantial, but no clear patterns have yet been identified. How do deafblind individuals process sensory input? Studies on deafblindness have mostly focused on single cases or groups of late-blind individuals. Importantly, the language backgrounds of deafblind communities are highly variable and include the usage of tactile languages. So far, this kind of linguistic experience and its consequences have not been considered in studies on basic perceptual functions. Here, we will provide a critical review of the literature, aiming at identifying determinants for neuroplasticity and gaps in our current knowledge of somatosensory processing in deaf and deafblind individuals.

Exploring conceptual representation and grounding through perceptual strength norms in deaf individuals

“…The brain areas traditionally associated with the processing of sounds (i.e., the auditory cortex) can respond also to tactile stimulation in humans (e.g., Foxe et al, 2002) and other animals (e.g., macaque monkeys: Kayser et al, 2005). However, it is precisely in deaf individuals that this interaction becomes most pronounced, as evidenced primarily in brain imaging research that documented strong responses to haptic stimuli in the deafferented auditory cortex of congenitally deaf participants (Auer et al, 2007;Karns et al, 2012; for review see: Villwock & Grin, 2022). In such a context, it may be speculated that for hearing individuals, it would be advantageous to keep audition and haptic inputs clearly distinct, given the great margin for ambiguity related to their mutual overlap from physiology to neural processing.…”

Identifying Patterns of Tactile Exploratory Behaviors in Children With Vision Impairment and Multiple Disabilities

“…Finally, it can be argued that more studies are required to be conducted on tactile exploratory activities in individuals with vision impairment and multiple disabilities, in order to deepen our understanding in the development of their somatosensory system and therefore design and conduct more effective personalized and early intervention programs (Villwock & Grin, 2022;Withagen et al, 2010).…”