Sex-linked left lateralized central processor for hierarchically-structured material? Evidence from Broca's aphasia

Based on a study with seven nonfluent aphasics, Grossman (Neuropsychologia 18, 299-308, 1980) advanced the 'central processor' claim that the mental representation of hierarchical linguistic structure is functionally equivalent to processing hierarchically-structured, nonlinguistic forms. Grossman reported that both abilities are compromised in Broca's aphasia. We attempted to replicate this effect with eight nonfluent aphasics using essentially the same task requiring the reconstruction from memory of stick designs. With the addition of controls for post-stroke interval, responding hand and gender, only the female aphasics had difficulty executing the hierarchical arrangement of visual-spatial materials. This sex difference disputes the strong form of the central processor hypothesis and supports the view that females may be more likely to possess partial noncomplementarity of specialization (dependence on the same hemisphere for selective language and spatial functions).