![]() Third, frontal compensation has been investigated in older adults because higher prefrontal activation is more prevalent in older adults than in younger adults during several cognitive tasks ( Cabeza et al., 2003 Gutchess et al., 2005 Davis et al., 2008 Heuninckx et al., 2008 Eyler et al., 2011 Cabeza and Dennis, in press). (2010) reported that the dedifferentiation of neural responses in older adults is associated with a reduction of the distinctiveness of within-category representations in the ventral-visual cortex. Ventral-visual activity in older adults is characterized by the dedifferentiation of responses to different stimuli categories, such as faces and/or houses ( Park et al., 2004). Second, a loss of regional specialization or declining specificity, referred to as dedifferentiation, has been hypothesized to occur in older adults ( Reinert, 1970 Lindenberger and Baltes, 1994 Chee et al., 2006 Voss et al., 2008). By reviewing age-related differences in prefrontal cortex activity during working memory and episodic memory tasks, Rajah and D’Esposito ( 2005) reported both age-related decreases and increases of activity in specific prefrontal regions. ![]() This frontal lobe overactivation has been reported in episodic memory, working memory, and perceptual tasks ( Grady et al., 1995, 1998 Cabeza, 2002 Grady, 2008). First, an overactivation of some cortical areas and a reduction in the hemispheric asymmetry of activation has been documented in older adults as compared to younger adults during cognitive task execution ( Grady et al., 1992 Backman et al., 1997 Cabeza, 2002 Park and Reuter-Lorenz, 2009). Structural imaging results have also demonstrated widespread gray and white matter tissue atrophy, which largely occurs in the frontal cortex (e.g., Raz et al., 2005).īased on evidence primarily acquired via non-invasive functional neuroimaging, four principal hypotheses have been postulated to explain the relationship between age-related neuronal activity changes and cognitive performance ( Reuter-Lorenz and Park, 2010). In addition, it has been clearly demonstrated that processing speed, memory, and executive functions depend on the “well-being” of several neuronal substrates ( Kennedy and Raz, 2009). Progress regarding the study of physiological and pathological brain aging achieved over the last two decades has provided strong evidence of neurophysiological correlates of cognitive and behavioral changes associated with aging.įor example, studies at the neuronal level have demonstrated that dopaminergic decline and gray matter atrophy are both correlated with specific cognitive changes in older adults ( Brody, 1955 Coleman and Flood, 1987 West et al., 1994 Small et al., 2002 Resnick et al., 2003 Sowell et al., 2003 Burke and Barnes, 2006 Kramer et al., 2007). One of the primary areas of investigation in neuroscience is age-related brain changes and the associations between these changes and changes in cognitive (e.g., language) function. Potential theories underlying the bilateral involvement of the prefrontal cortex are discussed, and the relationship between the bilateral engagement of the prefrontal cortex and the age or degree of pathology is explored. Moreover, it is suggested that in older adults and patients with dementia, the right prefrontal cortex is also engaged during naming tasks, and naming performance correlates with age and/or the degree of the pathological process. The results of this research suggest that the left frontal and temporal areas are crucial during naming. The present paper reviews studies that have applied NIBS in younger and older adults and in patients with dementia to track changes in the cerebral areas involved in a language task (naming). A technique that can be used to investigate changes in physiological and pathological aging is non-invasive brain stimulation (NIBS). These functional modifications have been linked to residual brain plasticity mechanisms, suggesting that all areas of the brain remain plastic during physiological and pathological aging. These functional changes are believed to favor positive reorganization driven by adaptations to system changes as compensation for cognitive decline. ![]() Over the last two decades, age-related anatomical and functional brain changes have been characterized by evidence acquired primarily by means of non-invasive functional neuroimaging. 2 Department of Clinical and Experimental Sciences, National Neuroscience Institute, University of Brescia, Brescia, Italy.1 IRCCS Centro San Giovanni di Dio Fatebenefratelli, Brescia, Italy.
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