Neuronal networks in the prefrontal cortex mediate the highest levels of cognitive processing and decision making, and the capacity to perform these functions is among the cognitive features most vulnerable to aging. Despite much research, the neurobiological basis of age-related compromised prefrontal function remains elusive. Many investigators have hypothesized that exposure to stress may accelerate cognitive aging, though few studies have directly tested this hypothesis and even fewer have investigated a neuronal basis for such effects. It is known that in young animals, stress causes morphological remodeling of prefrontal pyramidal neurons that is reversible. The present studies sought to determine whether age influences the reversibility of stress-induced morphological plasticity in rat prefrontal neurons. We hypothesized that neocortical structural resilience is compromised in normal aging. To directly test this hypothesis we used a well characterized chronic restraint stress paradigm, with an additional group allowed to recover from the stress paradigm, in 3-, 12-, and 20-month-old male rats. In young animals, stress induced reductions of apical dendritic length and branch number, which were reversed with recovery; in contrast, middle-aged and aged rats failed to show reversible morphological remodeling when subjected to the same stress and recovery paradigm. The data presented here provide evidence that aging is accompanied by selective impairments in long-term neocortical morphological plasticity.
Friday, June 04, 2010
Aging brains are less able to recover from the effects of stress
It is well documented that aging reduces the effectiveness of our prefrontal cortex in mediating cognitive processing and decision making, including working memory and flexible use of mental strategies. Bloss, McEwen et al. have now conducted studies that suggest that one reason for this decline may be that aging reduces the ability of prefrontal cortex to recover from stress-induced damage. Their abstract: