Temporal memory and content memory for actions: adult age differences in acquisition and retention

AGING, CONTEXT MEMORY AND BINDING: A COMPARISON OF “WHAT, WHERE AND WHEN” IN YOUNG AND OLDER ADULTS

There is evidence that age-related memory decline does not effect all types of episodic information to an equal extent, but that especially contextual memory and the integration of multiple features in memory deteriorate. The current study investigates contextual memory in a group of healthy young (N = 40) and older (N = 40) adults without dementia. All participants performed a computerized memory task assessing target memory (objects only), contextual memory (positions only) and memory for the combinations of two features (object, space, temporal order), that is, binding of target-context or context-context features. The results showed age-related decline on all task conditions. Furthermore, the performance on conditions requiring the binding of target and context features was affected to a greater extent in older adults compared to younger adults. These findings support the notion that a decline in contextual memory and binding might underlie poorer episodic memory in older participants.

Neuroanatomical and cognitive mediators of age-related differences in episodic memory

Aging is associated with declines in episodic memory. In this study, the authors used a path analysis framework to explore the mediating role of differences in brain structure, executive functions, and processing speed in age-related differences in episodic memory. Measures of regional brain volume (prefrontal gray and white matter, caudate, hippocampus, visual cortex), executive functions (working memory, inhibitory control, task switching, temporal processing), processing speed, and episodic memory were obtained in a sample of young and older adults. As expected, age was linked to reduction in regional brain volumes and cognitive performance. Moreover, neural and cognitive factors completely mediated age differences in episodic memory. Whereas hippocampal shrinkage directly affected episodic memory, prefrontal volumetric reductions influenced episodic memory via limitations in working memory and inhibitory control. Age-related slowing predicted reduced efficiency in temporal processing, working memory, and inhibitory control. Lastly, poorer temporal processing directly affected episodic memory. No direct effects of age on episodic memory remained once these factors were taken into account. These analyses highlight the value of a multivariate approach with the understanding of complex relationships in cognitive and brain aging.

Explaining age differences in temporal working memory

To determine the cognitive mechanisms underlying age differences in temporal working memory (WM), the authors examined the contributions of item memory, associative memory, simple order memory, and multiple item memory, using parallel versions of the delayed-matching-to-sample task. Older adults performed more poorly than younger adults on tests of temporal memory, but there were no age differences in nonassociative item memory, regardless of the amount of information to be learned. In contrast, a combination of associative and simple order memory, both of which were reduced in older adults, completely accounted for age-related declines in temporal memory. The authors conclude that 2 mechanisms may underlie age differences in temporal WM, namely, a generalized decline in associative ability and a specific difficulty with order information.

Age-related differences in the course of cognitive skill acquisition: the role of regional cortical shrinkage and cognitive resources

This study examined the impact of age-related differences in regional cerebral volumes and cognitive resources on acquisition of a cognitive skill. Volumes of brain regions were measured on magnetic resonance images of healthy adults (aged 22-80). At the early stage of learning to solve the Tower of Hanoi puzzle, speed and efficiency were associated with age, prefrontal cortex volume, and working memory. A similar pattern of brain-behavior associations was observed with perseveration measured on the Wisconsin Card Sorting Test. None of the examined structural brain variables were important at the later stages of skill acquisition. When hypertensive participants were excluded, the effect of prefrontal shrinkage on executive aspects of performance was no longer significant, but the effect of working memory remained.

Source monitoring: ERP evidence for greater reactivity to nontarget information in older adults

Event-Related Potentials (ERPs) were collected concurrently with stimulus presentation during a source monitoring task. Younger adults were less likely than older adults to make source monitoring errors and their ERP records showed far greater discrimination between target stimuli and familiar but nontarget foils. Older adults not only made more source errors but produced high amplitude late positivities to the nontarget foils even when these foils were correctly rejected. Under divided attention conditions, younger adults performance was similar to that of the older adults both behaviorally and electrophysiologically. These data illustrate the role that attentional resources play in the ability to inhibit response tendencies and suggest that age differences in source monitoring may be more related to attentional control than inefficiencies in the encoding of contextual information. As well, they suggest that the ERP late positivity may represent a more general response to item salience rather than serve as an index of recollection as is the current view.

Content memory and temporal memory for actions in survivors of traumatic brain injury

Memory for performed actions, a rehearsal-independent form of memory, was compared to verbal memory in 30 survivors of traumatic brain injury (TBI) and 30 demographically matched controls. Subjects were tested on recognition and recall memory for the content of recently performed actions in the laboratory, as well as the ability to reconstruct the temporal order in which the actions were performed. Each subject performed actions under incidental and intentional memory instructions. Half of the subjects performed 12 actions, the other half 24 actions, with an equal number of usual and unusual actions in each list. Verbal memory was assessed with paired-associate and temporal order tests. Although recall was more proficient overall for the control compared to the brain-injured subjects on both content and temporal memory for actions, memory for actions was better than verbal memory in both groups. Both groups performed better overall on the short compared to the long list of actions and recalled unusual actions better than usual actions. The rehearsal-independent nature of action memory was supported, with no advantage for the intentional instruction. It is proposed that a retrieval deficit may be in part responsible for deficits in memory for actions following TBI. However, preserved ability to benefit from the abundant contextual cues available through motor actions may account for the better recall of actions compared to words.

Adult age differences in temporal memory for cyclic actions

Adult age differences in temporal memory for bipolar or cyclic actions were investigated in three experiments. Cyclic actions are ones that have opposite poles in regard to their effect on an object (e.g., opening and closing a purse). For such actions, the critical memory function is to remember which pole occurred last. Temporal memory was tested by having subjects judge which component of a series of bipolar actions had been performed more recently (e.g., opening or closing a purse). Recency judgments were found to be as accurate under incidental memory conditions as they were under intentional memory conditions for both young and elderly adults. The accuracy of recency judgments was less for bipolar actions performed in three cycles than for bipolar actions performed in one cycle for both young and elderly adults. Adult age differences in the accuracy of recency judgments were found to be negligible.

Variation in external context and adult age differences in action memory

Adult age differences were determined for the memory and retention of the content of actions. Variation in the physical context from the time of performance of the actions to the time of testing for their memory had no effect for either young or elderly adult subjects on the recall or the recognition of the actions either shortly after acquisition or 24 hours later. Both young and elderly subjects showed significant forgetting of actions over a 24-hour retention interval as measured by recall.