Reply to Fjell et al. (2010) and Raz and Lindenberger (2010): The prevalence of cortical gray matter atrophy may be overestimated in the healthy aging brain.

Burgmans et al. (2009) stated that the prevalence of cortical gray matter atrophy may be overestimated in the healthy aging brain, because the inclusion of participants with preclinical cognitive pathology might have been responsible for the age effects found in previous studies. Fjell et al. (2010) and Raz and Lindenberger (2010) verified this statement by reanalyzing previously published data. They both argue that it is unlikely that preclinical cognitive pathology explains cortical gray matter atrophy in healthy aging. Burgmans et al. (2010) respond to these commentaries. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Aging does not affect gray matter asymmetry.

Previous research has shown that asymmetry of brain activity is decreased in older adults. This study investigates whether cortical gray matter asymmetry also shows age-related differences, and whether gray matter asymmetry differs between cognitively stable persons and persons who have shown profound age-related declines in cognitive functioning. In addition, we have examined whether prodromal dementia affects the study outcome. The gray matter volumes of seven prefrontal and temporal regions of interest were delineated on T1-weighted MRI scans in 70 adults aged between 52 and 84 years. Statistical analyses were conducted with and without participants who developed dementia within 6 years after the MRI scan session. It was found that asymmetry did not differ over the age range of 52–84 years of age. This result did not change when data from participants who were diagnosed with dementia within 6 years after MRI assessment were excluded from the analysis. In addition, no gray matter asymmetry differences were found between cognitively stable participants and participants who showed cognitive decline. We conclude that alterations in gray matter asymmetry may not be part of the healthy aging process. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The prevalence of cortical gray matter atrophy may be overestimated in the healthy aging brain.

Prevailing opinion holds that normal brain aging is characterized by substantial atrophy of cortical gray matter. However, this conclusion is based on earlier studies whose findings may be influenced by the inclusion of subjects with subclinical cognitive disorders like preclinical dementia. The present magnetic resonance imaging study tested this hypothesis. Cognitively healthy subjects (mean age 72 years, range 52–82) who remained cognitively stable over a 3-year period were compared to subjects with significant cognitive decline. Subjects who developed dementia within 6 years after the scan session were excluded. The gray matter volumes of seven cortical regions were delineated on T1-weighted magnetic resonance imaging scans. Participants without cognitive decline did not exhibit an age effect on the gray matter volume. Conversely, participants with cognitive decline exhibited a significant age effect in all the seven areas. These results suggest that cortical gray matter atrophy may have been overestimated in studies on healthy aging, since most studies were unable to exclude participants with a substantial atypical cognitive decline or preclinical dementia. Our results underscore the importance of establishing stringent inclusion criteria for future studies on normal aging. (PsycINFO Database Record (c) 2010 APA, all rights reserved)