Imaging
As with young and middle-aged adults, neuroimaging studies suggest that SMC
reflect underlying changes in brain structure and/or function. Saykin et al. ( 2006 )
reported that participants with SMC (n= 40), like those with MCI (n= 40), showed
a similar pattern of reduced gray matter density in specific brain regions critical for
memory performance, including the hippocampus. Figure13.2 highlights the
specific regions of the hippocampus where volume was decreased as levels of SMC
increased; the right hippocampus showed extensive volume loss as SMC increased.
To put thesefindings in context, the magnitude of volume loss in participants with
SMC was compared quantitatively to participants with no SMC, with MCI, and
with dementia. As shown in Fig.13.3, the individuals with SMC had lower vol-
umes than those without complaints (“healthy controls”: HC) but more than indi-
viduals with MCI, suggesting that SMC fall along a continuum between normal
aging and dementia (Saykin et al. 2006 ). Similarly, in a study of 503 subjects aged
between 50 and 85 years, SMC were associated with decreased hippocampal vol-
umes on structural MRI (van Norden et al. 2008 ).
Functional neuroimaging studies suggest that SMC may also reflect changes in
brain function. In a neuroimaging study of 75 older adults from the BLSA, SMC, as
assessed by validated questionnaire, were associated with increased activity in
specific brain regions, including the insula, lingual gyrus, and cerebellum during
memory tasks. SMC were unrelated to memory task performance in cross-sectional
analyses but predicted declines in verbal memory longitudinally (Hohman et al.
2011 ). SMC were also linked to markers of brain function during an attention test in
a small fMRI study involving patients from a memory clinic. Participants with
spontaneous SMC, defined as a self-perceived memory deficit significant enough to
seek evaluation from a healthcare provider, but normal cognition were compared to
those with no SMC. Participants with SMC did not differ from controls on cognitive
Fig. 13.2 Higher levels of cognitive complaints were associated with decreased gray matter
density (GMD) in theleftandrighthippocampi across the entire sample (n= 120,p< 0.001). The
yellowhighlight indicates those regions of interest (hippocampi) that showed decreased GMD. The
large area ofyellowon theright sideillustrates the extensive volume loss in the right hippocampus
as SMC increased. Reproduced with the permission from Saykin et al. ( 2006 )
286 M.T. Weber and P.M. Maki