Changes with Ageing

Changes with Ageing

1. Structural

   • Grey matter
   • White matter
     • Kochunov et al. (2007): myelination shows quadratic pattern w/ age; demyelination w/ age; GM thickness and fractional anisotropy decrease; sulcal span increases (result of GM and WM decrease)
       • differential WM ageing: heterochronicity & regional heterogeneity (last-in-first-out): e.g. corpus callusum
       • Function: connectivity of cerebral network decreases, decline of higher cogn. function
     • Salat et al. (2009): WM volume decreases in healthy ageing (mainly frontal lobe); additional regions in AD; preserved until 50s >> quadratic function
     • Chee et al. (2009): cogn. decline, GM & WM reduced equally w/ age, cerebral volume (WM+GM)~cogn. performance, education ~ cogn. decline but not volume reduction; homocysteine~both cognition & volume

2. Functional: memory

   • Morcom et al. (2003): bilateral PFC and hippocampal activity in older Pp during encoding >> compensatory or differentiation due to 1) failure to recruit specialised area 2) failure to inhibit other areas 3) other cogn. processing strategies
   • Duverne et al. (2008): reduced asymmetry only in poor older performers
   • Wang et al. (2009): over-recruitment plateaus in advanced age (80s/90s) despite further decrease in cogn. performance
   • Seidenberg et al. (2009): more activation & in more areas associated w/ AD risk factors

3. Functional: Default Mode Network

   • Damoiseaux et al. (2008): less activity in DMN ~ cogn. decline
   • DeLong et al. (2012): older adults with high verbal fluency make linguistic predictions when cued with indefinite articles (like young Pp), older adults with low/medium verbal fluency don’t
   • Paxton et al. (2006): older adults use reactive strategy (no predictions but retrieval from memory); not due to memory failure and can be trained to use proactive strategy
   • Buckner et al. (2008): in AD< medial temporal lobe esp. affected >> memory decline; metabolism hyp. of beta amyloid accumulation
   • Xu et al. (2014): concentrative meditation decreases DMN activity