Do non-language regions become language regions? The case of deprived sensory cortices

The frontotemporal language network is functionally specialized for language processing and activates only to linguistic processing. Whether other regions can acquire this function is a key issue in neuroplasticity as it remains unclear whether cortical regions can ever change their specializations. Deprived sensory cortices, i.e., visual cortices of the blind and the auditory cortices of the deaf, have been the strongest candidate for this. These regions cannot perform their original function and have all the impetus to change. Indeed, numerous studies have shown their activation during various language tasks and have suggested that these regions acquire linguistic processing functions. However, activation during language tasks does not imply activation to linguistic processing. These activations could have been due to the accompanying sensory processing or domain-general task demands. We had congenitally blind, deaf, sign-language-using children of deaf parents, and sighted and hearing controls, do two language tasks. Blind participants additionally did a series of cognitive control tasks. We found that neither the visual cortices in the blind nor the auditory cortices in the deaf activated to linguistic processing. Visual cortices in the blind, like the multiple-demand frontoparietal regions, activated only when the language task was accompanied by domain-general demands, and not when language was to be processed in their absence. In contrast, the canonical language regions activated during any linguistic processing, regardless of the accompanying task demands. Crucially, the visual cortical voxels that activated during the demanding language task also activated in response to a host of non-linguistic cognitive control demands but not when linguistic processing occurred in the absence of task demands, showing that these regions were indeed activated by domain-general demands. Likewise, auditory regions in the deaf showed no activation to linguistic processing, and instead activated to sensory processing demands. Linguistic processing in them was again limited to the canonical language regions. Deprived sensory cortices, contrary to many claims, do not become language regions.