The purpose of this review is to extend the existing application of the frontal lobe hypothesis of cognitive aging beyond the limited work on inhibitory control (F. N. Dempster, 1992) to include memory processes supported by the prefrontal cortex. To establish a background for this analysis, I review existing models of prefrontal cortex function and present a synthesized model that includes a general function of temporal integration, supported by 4 specific processes: prospective memory, retrospective memory, interference control, and inhibition of prepotent responses. I found the frontal lobe hypothesis to perform well, with the exception of an inability to account for age-related declines in item recall and recognition memory, possibly a result of age-related declines in medial temporal function.

An application of prefrontal cortex function theory to cognitive aging.

An associative hypothesis to explain and predict older adults' deficient explicit episodic memory performance was outlined and tested. The hypothesis attributes a substantial part of older adults' deficient memory performance to their difficulty in merging unrelated attributes-units of an episode into a cohesive unit. Although each of the components can be memorized to a reasonable degree, the associations that tie the attributes-units to each other grow weaker in old age. Four experiments are reported that provide (a) a converging validity to the hypothesis by demonstrating this associative deficit for both interitem relationships and intraitem relationships and (b) a discriminant validity to the hypothesis by contrasting and testing competing predictions made by the associative hypothesis and by alternative hypotheses. The implications of these results to older adults' episodic memory performance are discussed.

Adult age differences in memory performance: Tests of an associative deficit hypothesis.

Numerous empirical and theoretical observations point to the constructive nature of human memory. This paper reviews contemporary research pertaining to two major types of memory distortions that illustrate such constructive processes: (a) false recognition and (b) intrusions and confabulations. A general integrative framework that outlines the types of problems that the human memory system must solve in order to produce mainly accurate representations of past experience is first described. This constructive memory framework (CMF) emphasizes processes that operate at encoding (initially binding distributed features of an episode together as a coherent trace; ensuring sufficient pattern separation of similar episodes) and also at retrieval (formation of a sufficiently focused retrieval description with which to query memory; postretrieval monitoring and verification). The framework is applied to findings from four different areas of research: cognitive studies of young adults, neuropsychological investigations of brain-damaged patients, neuroimaging studies, and studies of cognitive aging.

https://scholar.harvard.edu/files/schacterlab/files/schacternormankoutstaal1998.pdf

The cognitive neuroscience of constructive memory

Most theories of spoken word identification assume that variable speech signals are matched to canonical representations in memory. To achieve this, idiosyncratic voice details are first normalized, allowing direct comparison of the input to the lexicon. This investigation assessed both explicit and implicit memory for spoken words as a function of speakers' voices, delays between study and test, and levels of processing. In 2 experiments, voice attributes of spoken words were clearly retained in memory. Moreover, listeners were sensitive to fine-grained similarity between 1st and 2nd presentations of different-voice words, but only when words were initially encoded at relatively shallow levels of processing. The results suggest that episodic memory traces of spoken words retain the surface details typically considered as noise in perceptual systems.

/pdf/words-and-voices-episodic-traces-in-spoken-word-530zf9bi06.pdf

Words and voices: episodic traces in spoken word identification and recognition memory.

The authors reviewed the evidence of age differences in episodic memory for content of a message and the context associated with it. Specifically, the authors tested a hypothesis that memory for context is more vulnerable to aging than memory for content. In addition, the authors inquired whether effort at encoding and retrieval and type of stimulus material moderate the magnitude of age differences in both memory domains. The results of the meta-analysis of 46 studies confirmed the main hypothesis: Age differences in context memory are reliably greater than those in memory for content. Tasks that required greater effort during retrieval yielded larger age differences in content but not in context memory. The greatest magnitude of age differences in context memory was observed for those contextual features that were more likely to have been encoded independently from content. Possible mechanisms that may underlie age differences in context memory-attentional deficit, reduced working memory capacity, and failure of inhibitory processing are discussed.

Differential effects of aging on memory for content and context: a meta-analysis.

Previous research has established that elderly adults can exhibit impaired memory for the source of newly acquired facts even when levels of fact recall in old and young do not differ. However, source memory impairments have been observed only under conditions of many-to-1 mapping: A large number of facts are related to either of 2 sources. It is thus possible that apparent source memory impairments reflect a more general age-related problem in handling many-to-1 mappings. Two experiments provide evidence against this possibility by demonstrating age-related source memory deficits with 1-to-1 mapping between facts and sources. The data also indicate that source memory deficits are observed across encoding tasks that manipulate the allocation of attention to the source or to the fact.

Source memory: Extending the boundaries of age-related deficits

Previous research has shown that elderly adults often exhibit intact priming effects on visual implicit memory tests, but little is known about auditory priming and ageing. We examined priming effects on auditory stem-completion and filter identification tasks in older and younger adults. Young subjects showed more priming when speaker's voice was the same as study and test than when it differed, but elderly subjects failed to exhibit this voice-specific priming effect in each of five experiments. The elderly did, however, show robust nonspecific priming. We attempt to rule out hearing deficit accounts of the priming impairment and consider alternative theoretical interpretations of the effect.

Dana M. Osowiecki

Papers

Source memory: Extending the boundaries of age-related deficits

Auditory priming in elderly adults: impairment of voice-specific implicit memory.