What does unilateral hearing loss tell us about the relationship between the motor cortical representation of language and auditory consciousness?

In this paper we highlight the relationship between auditory consciousness and the dorsal stream of language in brain by analysing the case of unilateral hearing loss. In subjects with unilateral hearing loss a cortical re-organization occurs. We analysed the few data available in literature on the cognitive performances and the cortical re-organization of subjects with unilateral hearing loss. We found that the ventral stream of linguistic perception seems not to be affected by cortical re-organization; on the contrary, the dorsal stream seems to become more bi-lateralized. Moreover, occipital activations occur. Brain imaging data suggest that subjects with unilateral hearing loss have difficulties in de-activating the default mode network and in activating the attentional processing. Some behavioural observations are in line with this datum. Therefore, the dorsal stream of language might be linked with auditory consciousness. Anomalous patterns of activation of superior temporal gyri in the clinical population took in consideration are in line with this idea. Despite the patients' pattern of activation seems to indicate a stronger effort by their brain to integrate linguistic stimuli in the flow of auditory consciousness, subjects with unilateral hearing loss show more difficulties than normal hearing subjects in activating attentional processes and in de-activating the default mode network. Behavioural and neurobiological data indicate that these difficulties seem stronger in case of right hearing loss than in case of left hearing loss. Further research is needed to confirm this hypothesis.