Impaired retention is responsible for temporal order memory deficits in mild cognitive impairment

Abstract

Temporal order memory, or remembering the order of events, is critical for everyday functioning and is difficult for patients with mild cognitive impairment (MCI). It is currently unclear whether these patients have difficulty acquiring and/or retaining such information and whether deficits in these patients are in excess of “normal” age-related declines. Therefore, the current study examined age and disease-related changes in temporal order memory as well as whether memory load played a role in such changes. Young controls (n=25), older controls (n=34), and MCI patients (n=32) completed an experimental task that required the reconstruction of sequences that were 3, 4, or 5-items in length both immediately after presentation (i.e., immediate recall) and again following a 10-minute delay (i.e., delayed recall). During the immediate recall phase, there was an effect of age largely due to reduced performance at the two longest span lengths. Older controls and MCI patients only differed during the 5 span (controls > MCI). During the delayed recall, however, there were significant effects of both age and MCI regardless of span length. In MCI patients, immediate recall was significantly correlated with measures of executive functioning while delayed recall performance was only related to other memory tests. These findings suggest that MCI patients experience initial temporal order memory deficits at the point when information begins to exceed working memory capacity and become dependent on medial temporal lobe functioning. Longer-term deficits are due to an inability to retain information, consistent with the characteristic medial temporal lobe dysfunction in MCI.

RBANS Memory Indices Are Related to Medial Temporal Lobe Volumetrics in Healthy Older Adults and Those with Mild Cognitive Impairment

“…These findings are consonant with the known role of the hippocampus in memory retention and previous research demonstrating that smaller hippocampal volume is associated with worse memory test performance (Arlt et al, 2013;Apostolova et al, 2010;Mungas et al, 2005). They also reinforce previous conclusions that the DMI, relative to the IMI, is more sensitive to memory impairment in those with AD (Duff et al, 2008) as well as our earlier report that MCI patients experience relatively intact encoding but impaired retention (Gillis, Quinn, Phillips, & Hampstead, 2013). The fact that virtually all of the memory subtests (i.e., those occurring after a time delay) were related to hippocampal volumes bilaterally likely reflects the bilateral nature of the presumed disease process (Apostolova et al, 2012).…”

Differences in temporal order memory among young, middle-aged, and older adults may depend on the level of interference

“…A recent study reported that impaired temporal order memory may be a selective behavioral marker of Alzheimer’s disease (Bellassen et al, 2012 ). In addition, temporal order memory deficits have been reported in older adults diagnosed with mild cognitive impairment (Gillis et al, 2013 ), which has been described as a transitional stage between normal aging and Alzheimer’s disease. Therefore, the present findings potentially may have both basic science and clinical implications.…”

Cognitive Rehabilitation of Memory for Mild Cognitive Impairment: A Methodological Review and Model for Future Research

“…Likewise, retrieving specific information will become especially challenging with the passage of time given the accumulation of pages (digital or physical), notes, or bookmarks. Although patients may be able to locate such information by referencing key events (e.g., holidays), patients with MCI have difficulty retaining the temporal aspects of information (Gillis, Quinn, Phillips, & Hampstead, 2013) and associating information ; for a review see Sperling, 2007); findings that suggest that such temporal or associative referencing will be especially challenging.…”