Читать книгу Pathy's Principles and Practice of Geriatric Medicine - Группа авторов - Страница 153

During ageing, communication and network activity within and between brain areas can be altered, with profound implications. For example, the excitatory imbalance resulting from impaired inhibitory signalling (e.g. GABA) can result in hyperexcitability and excitotoxicity. The dysregulation of other neurotransmitter systems (e.g. acetylcholine, dopamine, serotonin) has been linked with neurodegeneration and impaired brain function.^23,30

As a consequence of impaired neuronal network activity, synaptic plasticity mechanisms are also affected during ageing. Synaptic plasticity refers to mechanisms responsible for activity‐dependent modification of the strength or efficacy of synaptic transmission at pre‐existing synapses,³¹ thus representing the neurobiological substrate of learning and memory,³² and can be experimentally explored in vivo by non‐invasive brain‐stimulation techniques.³³ Advanced non‐invasive brain stimulation techniques have documented a progressive reduction of brain plasticity mechanisms with ageing³⁴ – similar to that observed in AD‐like and PD‐like conditions – responsible for cognitive and motor impairment.^35,36 Taken together, these observations contribute to the understanding of the clinical features observed during neurological examination of the elderly.