Brain Plasticity: Paradoxical Case of a Neurodegenerative Disease?

Neuronal Plasticity: Neuronal Organization is Associated with Neurological Disorders

Stimuli from stressful events, attention in the classroom, and many other experiences affect the functionality of the brain by changing the structure or reorganizing the connections between neurons and their communication. Modification of the synaptic transmission is a vital mechanism for generating neural activity via internal or external stimuli. Neuronal plasticity is an important driving force in neuroscience research, as it is the basic process underlying learning and memory and is involved in many other functions including brain development and homeostasis, sensorial training, and recovery from brain injury. Indeed, neuronal plasticity has been explored in numerous studies, but it is still not clear how neuronal plasticity affects the physiology and morphology of the brain. Thus, unraveling the molecular mechanisms of neuronal plasticity is essential for understanding the operation of brain functions. In this timeline review, we discuss the molecular mechanisms underlying different forms of synaptic plasticity and their association with neurodegenerative/neurological disorders as a consequence of alterations in neuronal plasticity.

Evidence for divergent effects of neurodegeneration in Huntington's disease on attentional selection and neural plasticity: implications for excitotoxicity

It is generally assumed that neurodegeneration leads to declines in cognitive functions. However, there is evidence that neurodegenerative processes related to excitotoxicity can lead to paradoxical improvements in circumscribed cognitive functions, while at the same time other processes are compromised. An open question is how such paradoxical improvements reported in literature and declines usually associated with neurodegeneration relate to each other. Do paradoxical improvements only reflect a transient phenomenon, or do they intensify in the course of neurodegeneration? We examine this question using behavioral and neurophysiological (EEG) data in a human model of excitotoxic neurodegeneration (i.e., Huntington's disease, HD). The results show that attentional selection processes decline during pre-manifest disease progression. Importantly, the efficacy of protocols used to induce neural plasticity in processes underlying attentional selection processes also increases in course of ongoing neurodegeneration in pre-manifest HD. This was reflected in behavioral data and electrophysiological correlates of processes related to the allocation of attention. To conclude, our results suggest that circumscribed enhancements of specific cognitive functions are as much a result of the developmental process of neurodegeneration as the well-known detrimental effects. The results account for the divergent effects of neurodegenerative processes closely related to excitotoxicity on cognitive functions.