Age‐related Changes in Cortical Blood Flow Activation during Perception and Memory

Abstract

Although many cognitive functions are affected by age, some are relatively maintained. There also are numerous age-related changes in brain structure, but not much is known about how these changes impact upon the alterations seen in cognition. In order to understand the basis for the reductions and sparings of cognitive function in the aged, experiments were carried out to compare regional cerebral blood flow (rCBF) and performance in young and old subjects on visual perceptual and memory tasks. In the first experiment, which examined the perception of faces and spatial locations, old subjects were as accurate as young subjects, and both groups had rCBF activation in fusiform gyrus during face matching and in superior parietal cortex during location matching. However, old subjects had less activation of prestriate cortex and more activation of frontal and lateral temporal cortex than did young subjects. The second experiment tested recognition memory for faces, a task on which old subjects were impaired. Young subjects had rCBF activation in left prefrontal and inferior temporal cortex and in right hippocampus during encoding of the faces, and in right prefrontal and parietal cortex during recognition. Old subjects showed no significant activation of the areas involved in encoding, but did have increased rCBF in right prefrontal cortex during recognition. These results suggest that the aging brain can demonstrate alterations of the functional systems involved in some cognitive processes, such as perception, that may serve as a compensatory mechanism to maintain performance. Failure to show such compensation, coupled with dysfunction of the areas primarily involved in processing may lead to more marked deficits in performance.

Structure and function of the aging brain

“…Moreover, unlike the lateralized pattern of functional activity within the prefrontal cortex observed in the young, older participants demonstrated greater bilateral activation [79]. Since this seminal work, this pattern of decreased lateralization in functional brain response in aging has been replicated in numerous reports using both PET and fMRI methods, and spanning a range of cognitive domains including memory encoding and retrieval [80][81][82][83][84], visual attention [80][81][82][83][84][85]; working memory [80][81][82][83][84][86][87][88][89], as well as selective attention and inhibition [90].…”

Cortical reorganization of language functioning following perinatal left MCA stroke

“…Such a decrease in intrahemispheric inhibition allows for participation of other, possibly previously dormant brain areas in maintaining cognitive functions as the brain ages. 65,66 Overall, the data presented here provide additional knowledge of neuroplasticity following an early injury to the immature brain. In addition to the overall shift of expressive language dominance to the right hemisphere, this study also provides new information that can be useful for the design of future experiments addressing the issues of language recovery after stroke in children and adults.…”

Recent developments of functional magnetic resonance imaging research for drug development in Alzheimer's disease

“…The complex interplay between dysfunctional and adaptational processes in the brain was shown in functional activation neuroimaging studies in older healthy subjects Grady 1996;Grady 2002;Grady et al 2002;Grady et al 2003;Damoiseaux et al 2008;Grady et al 2008), in subjects at high risk to develop AD (Dickerson et al 2005;Rombouts et al 2005;Bartres-Faz et al 2008;Bokde et al 2008;Bosch et al 2010) or with already manifest AD (Horwitz et al 1995;Pihlajamaki et al 2008;Rosenbaum et al 2008;Dickerson et al 2009;Rombouts et al 2009;. A large array of functional activation studies performed with a variety of multimodal activation paradigms revealed a high level of heterogeneity across experiments and study groups, making it very difficult to create generally valid interpretations of these imaging data.…”