MOM 2006 journal for pdf.pmd - University of Michigan-Flint
MOM 2006 journal for pdf.pmd - University of Michigan-Flint
MOM 2006 journal for pdf.pmd - University of Michigan-Flint
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ADULT AGE DIFFERENCES IN LETTER AND CATEGORY FLUENCY:<br />
NEUROANATOMICAL IMPLICATIONS<br />
Carissa Broadbridge and Rebecca Anders<br />
Faculty Sponsor: Debra McGinnis<br />
Department <strong>of</strong> Psychology, Oakland <strong>University</strong><br />
Abstract<br />
People <strong>of</strong> all ages tend to generate more words when presented with a category (category<br />
fluency) than when presented with the initial letter (letter fluency). The present study (N=128)<br />
reveals age-related declines in category fluency, F (2, 125) = 10.197, p < .001 with old-old adults<br />
per<strong>for</strong>ming worse than the other age groups. In contrast, letter fluency was associated with<br />
stability across the life span. This age-related category-letter dissociation may be due to the agerelated<br />
declines in brain areas recruited across recall tasks with left temporal activity associated<br />
with category recall and left frontal activity with letter recall (Capitani, Laiacona, & Basso,<br />
1998). This study augments the cognitive aging literature by including a sizable sample <strong>of</strong> adults<br />
older than 75.<br />
Background<br />
Cognitive Aging and the Fourth Age<br />
Virtually all cognitive processes are subject to the negative consequences <strong>of</strong> human aging<br />
(Backman, Small, Wahlin, & Larsson, 2000). Recent studies <strong>of</strong> adults after the age <strong>of</strong> 75 suggest<br />
that the rate <strong>of</strong> decline may increase after that age. Baltes (1997) refers to this part <strong>of</strong> the life<br />
span as the fourth age, with his data suggesting that this is a time when cognitive declines can be<br />
precipitous in a noticeable proportion <strong>of</strong> older adults.<br />
Category and Letter Fluency<br />
Semantic memory is among those processes consistent with a rate change in late life, with no<br />
or minimal decline be<strong>for</strong>e 75, after which deterioration is gradual in most individuals (Backman<br />
et al., 2000). Ability to recall in<strong>for</strong>mation is <strong>of</strong>ten tested through verbal fluency. Among all age<br />
groups, there is a lower rate <strong>of</strong> recall in letter fluency tasks than in category fluency tasks<br />
(Rodriguez-Aranda, 2003; Brickman, Paul, Cohen, Williams, MacGregor, Jefferson, Tate,<br />
Gunstad, & Gordon, 2005). In addition to this, while letter fluency may remain relatively stable<br />
over the lifetime, category fluency tends to decline as age increases (Rodriguez-Aranda, 2003;<br />
Brickman et al., 2005).<br />
Frontal Lobe Hypothesis<br />
Some cognitive aging scientists propose that the frontal lobes may be associated with<br />
significant age-related deterioration, affecting processes dependent on these neuroanatomical<br />
areas (Woodruff-Pak, 1997; Kaszniak & Newman, 2000). Because letter fluency is among the<br />
processes dependent on frontal lobe integrity (Lezak, 1995), age-related changes to the frontal<br />
lobe may result in letter fluency declines in affected individuals. This dissociation implies that<br />
age-related degenerative processes may result in greater declines in frontal lobe processes, such<br />
as letter fluency, compared to temporal processes, such as category fluency.<br />
Meeting <strong>of</strong> Minds <strong>2006</strong> 18