Sensorimotor contingencies in congenital hearing loss: The critical first nine months.

In the recent two decades it became possible to compensate severe-to-profound hearing loss using cochlear implants (CIs). The data from implanted children demonstrate that hearing and language acquisition is well-possible within an early critical period of 3 years, however, the earlier the access to sound is provided, the better outcomes can be expected. While the clinical priority is providing deaf and hard of hearing children with access to spoken language through hearing aids and CIs as early as possible, for most deaf children this access is currently in the second or third year of life. We review the findings on neural development during the first year of life, including language development, multimodal interactions between sensory and motor systems, as well as brain connectivity. Some irreversible consequences of early auditory deprivation within the first year are exacerbated when the auditory system is not developed in synchrony with the other sensory and motor systems, incorporating hearing into other sensory and motor representation. The key role of the motor system (sensorimotor contingencies) in development of sensory representations is discussed. We propose that the first year includes critical developmental steps that should be exploited to provide the framework for optimal functional connectivity of language and cognitive networks.