Hemispheric Disconnection and Neurodegeneration: Cross-Disciplinary Approaches to Apraxias and Alzheimer’s

AbstractIntroduction: Alzheimer's is a neurodegenerative disease characterized by a progressive decline in cognitive and motor functions. This research proposes an innovative multimodal hypothesis. According to the hypothesis, the loss of emotionally engaging interests and goals in at-risk individuals leads to a reduction in conscious goal-oriented activities. Not only are enacted movements affected, but also those imagined during mental travels. Investigating these mechanisms can significantly accelerate research on apraxias and Alzheimer's. Method: A review of multidisciplinary literature on hemispheric connection and disconnection, proprioception, embodied cognition, motor language, and the syntax and semantics of gestural actions, among other topics, is employed to support the proposed hypothesis. From theoretical speculation, entirely new interpretations of motor-cognitive degenerations emerge. Discussion: Healthy connectivity between the dominant and contralateral hemispheres consists of a functional tension where data integration is complementary. The left hemisphere articulates already learned gestures into chains experienced as advantageous for achieving a goal, working towards maximum efficiency in goal-oriented action. In contrast, the right hemisphere provides a repertoire of gestural units with intrinsic meaning, independent of chains, to be used when execution on the left is interrupted or when more creative solutions are required. Conclusion: The lack of interhemispheric dialogue results in the atrophy of neural contacts capturing contralateral inputs, with progressive necrosis leading to the formation of amyloid plaques and advanced cerebral atrophy. The root cause of this lack of dialogue lies in the loss of value-driven motivations, particularly existential ones.