Nonright‐handedness, central nervous system and related pathology, and its lateralization: A reformulation and synthesis

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Abstract
A theoretical analysis of the associations between nonright‐handedness (NRH) and various neurodevelopmental disorders, psychopathology, and related medical conditions is presented. Fourteen disorders and conditions are reviewed in which elevated NRH has been alleged. Impaired noradrenergic activity and, to a lesser extent, serotonergic dysfunction are common to most of these disorders but are not always associated with elevated NRH. In contrast, dysfunction of the labyrinth, its neural projection areas, or both, apparently exists in all cases involving a proven elevation in NRH, but not in other disorders associated with neurochemical imbalances but normal percentages of right‐handedness. It is theorized that inputs from the vestibular system to the locus coeruleus, raphe nucleus, and other brainstem structures are critical to the development of motoric dominance and the lateralization of monoaminergic activity in the central nervous system, whereas the contribution of vestibular dysfunction to overall central nervous system neurochemical imbalances is considerably less significant.