Clinical Neurophysiology of Brain Plasticity in Aging Brain

Abstract

The pathophysiological mechanisms underlying normal aging and neurodegenerative disorders represent the focus of a bulk of recent research. Physiological brain aging is characterized by a progressive dysfunction and loss of synaptic contacts and neuronal abnormal apoptosis. Neural and synaptic redundancy as well as functional and structural plastic remodeling of brain networking promote maintenance of brain activity in healthy elderly for everyday life but are not sufficient to face the pathologic scenario of excessive synaptic/ neuronal loss as in dementias. It is, then, important to implement techniques that are able to measure changes in normal aging brain and to discriminate the threshold from neurodegenerative processes. Rhythmic electromagnetic brain oscillatory activity is a hallmark of neuronal function and it contains relevant traces of neuronal assemblies cooperation across different brain functions; an integrated approach utilizing modern neurophysiological techniques, including electroencephalography (EEG), event-related potentials (ERPs), and transcranial magnetic stimulation (TMS), together with biological markers and structural and functional imaging is promising for largescale, affordable, and non-invasive intercept of at-risk populations both at a group and probably also at a single-subject level. This approach might also guarantee the possibility of studying drug-induced changes in the electrical properties of the human cortex, developing and testing models of brain connectivity and treating neuropsychiatric diseases. In this paper some neurophysiological cutting-edge techniques will be presented that provide innovative information and deal with the broad issue of the role of neurophysiology for the assessment of patho-physiological aging and dementia also providing new insight to the actions of central nervous system drugs at the cortical level.

The visual cognitive network, but not the visual sensory network, is affected in amnestic mild cognitive impairment: A study of brain oscillatory responses

“…Our results indicated that there were increased visual SEO responses over the posterior parts of the hemispheres in AD patients (Yener et al, 2009). Several other reports also stated that there were increased motor evoked responses (Ferreri et al, 2011;Rossini et al, 2013aRossini et al, , 2013b, increased auditory evoked magnetoencephalography (MEG) responses (Osipova et al, 2006), and increased somatosensory responses in MCI/AD (Stephen, et al, 2010).…”

“…Oscillatory brain activity is a hallmark of neuronal network function and can accurately determine normal and abnormal brain functions. Brain oscillatory responses provide noninvasive analyses of cortico-cortical connectivity, local neuronal synchronization of firing, and coherence of rhythmic oscillations at various frequencies (Rossini et al, 2013a(Rossini et al, , 2013b. Event-related potentials (Papaliagkas et al, 2011) and oscillations (ERO) can be used as tools for detecting subtle abnormalities in cognitive processes, especially in dementia or related disorders.…”

Sensorimotor cortex excitability and connectivity in Alzheimer's disease: A TMS-EEG Co-registration study

“…This ability seems to be supported by cortical hyperexcitability that is a well-defined neurophysiological feature of AD, also evident in the early stages of the disease [Di Lazzaro et al, 2002Ferreri et al, 2003] and probably related to its severity and progression [Ferreri et al, 2011a;Khedr et al, 2011]. This has been indirectly evaluated by several transcranial magnetic stimulation (TMS) studies along the last twenty years [Cantone et al, 2014;Guerra et al, 2011;Rossini et al, 2013]. TMS observations have in fact demonstrated that motor cortex excitability is directly correlated with motor cortex plasticity in elderly subjects and demented patients [Guerra et al, 2015].…”

Age-Related Changes in Electroencephalographic Signal Complexity

“…Progressive brain dysfunction in physiological aging is primarily due to a loss of synaptic contacts and abnormal neuronal apoptosis [ 1 ]. In healthy elderly individuals, the maintenance of brain activity is promoted by neural and synaptic redundancy, as well as plasticity mechanisms secondary to physical and mental training, these remodel the brain both functionally and structurally [ 2 ].…”

“…Previous neurophysiological assessments by EEG described age related changes of resting state activity of the whole cortical mantle [ 3 – 5 ]. Indeed, progressive neural specialization and global integration of the brain networks during development and maturation, as well as the loss of synaptic connections and neuronal apoptosis in physiological brain aging, also result in a change of dynamics of the electrophysiological data [ 1 ].…”