Priming effects from young-old to very old age on a word-stem completion task: minimizing explicit contamination

Effects of age on the time course of syntactic priming in Chinese sentence production: an ERP study

Using a syntactic priming task, we investigated the time course of syntactic encoding in Chinese sentence production and compared encoding patterns between younger and older adults. Participants alternately read sentence descriptions and overtly described pictures, while event-related potentials (ERPs) were recorded. We manipulated the abstract prime structure (active or passive) as well as the lexical overlap of the prime and the target (verb overlap or no overlap). The syntactic choice results replicated classical abstract priming and lexical boost effects in both younger and older adults. However, when production latency was taken into account, the speed benefit from syntactic repetition differed between the two age groups. Meanwhile, preferred priming facilitated production in both age groups, whereas nonpreferred priming inhibited production in the older group. For electroencephalography, an earlier effect of syntactic repetition and a later effect of lexical overlap showed a two-stage pattern of syntactic encoding. Older adults also showed a more delayed and interactive encoding pattern than younger adults, indicating a greater reliance on lexical information. These results are illustrative of the two-stage competition and residual activation models.

Age differences in priming as a function of processing at encoding

It is unclear whether implicit memory (priming) is affected by aging. Some studies have reported no difference between young and older adults, while others have uncovered reliable reductions. An important factor that may explain these discrepancies is the manner of encoding. Processing requirements (perceptual/conceptual) have varied considerably between studies, yet processing abilities are not equally affected by aging. This study examined whether processing during encoding moderates age effects on priming. Young and older participants studied object-word pairs and made natural/manufactured (conceptual) and left/right rotation (perceptual) judgements in relation to the word or object. Objects served as targets on a subsequent continuous identification with recognition task to assess priming and recognition. Priming and recognition were greater in young than older adults for attended items, with a larger effect size in the conceptual than the perceptual condition. Findings suggest that age differences in priming may be a function of processing at encoding.

Age and processing effects on perceptual and conceptual priming

Explicit (declarative) memory declines with age, but age effects on implicit (nondeclarative) memory are debated. Some studies have reported null changes in implicit memory (e.g., priming in word-fragment completion, perceptual identification, category exemplar generation) with age, while others have uncovered declines. One factor that may account for these discrepancies is processing. Evidence suggests that conceptual and perceptual processes are not equally affected by ageing, yet processing requirements have varied greatly between studies. Processing may moderate age effects on priming, but no study has systematically examined this issue. This registered report presents an experiment to manipulate processing (conceptual / perceptual) during incidental encoding of words, prior to measures of perceptual (perceptual identification) and conceptual (category verification) priming. The perceptual and conceptual priming tasks were matched on all characteristics except processing, making them highly comparable. The four orthogonal conditions (perceptual encoding, perceptual test [PP]; conceptual encoding, perceptual test [CP]; perceptual encoding, conceptual test [PC]; conceptual encoding, conceptual test [CC]) were designed to clarify situations in which age effects on implicit memory emerge, which holds important practical and theoretical implications. Significant effects of Age, Test, and an Age × Processing interaction emerged. Priming was greater in young than older adults and on the perceptual than the conceptual test, but in contrast to the predictions, the age difference was only significant when prior encoding was perceptual (i.e., in the PP and CP conditions).

Priming Sentence Production in Older Adults: Evidence for Preserved Implicit Learning

Purpose

Structural priming- speakers' unconscious tendency to echo previously encountered message-structure mappings - is thought to reflect the processes of implicit language learning that occur throughout the lifespan. Recently, structural priming has also been used as a means to facilitate language re-learning in age-related language disorders such as aphasia. However, little evidence is available on whether structural priming remains effective in healthy aging, limiting clinical translation of the structural priming paradigm. This study examined the impact of aging on the strength and longevity of abstract structural priming and lexical boost effects.

Method

Twenty-four young and 24 older adults participated in a collaborative picture-matching task where the participant and experimenter took turns describing picture cards using transitive and dative sentences. In Experiment 1, a target was elicited immediately following a prime (0-lag), whereas two filler items were embedded between a prime and a target sentence in Experiment 2 (2-lag) to examine longer-term priming effects. In both experiments, the verb was repeated for half of the prime-target pairs to examine lexical boost on structural priming.

Results

At immediate priming, older adults showed both abstract structural priming and lexical boost in transitives and datives, similar to young adults. At longer-term priming, only abstract priming effects were significant in both groups of participants, with no evidence of age-related reduction in priming.

Conclusions

Both lexically-specific and independent mechanisms of structural priming remain resilient in older adults, supporting the view that structural priming reflects life-long language learning. Further, the findings provide empirical basis for applying structural priming to elderly clinical populations.

Experimental Investigation Examining the Effects of Acute Exercise on Implicit Memory Function

Emerging work suggests that acute exercise can enhance explicit memory function. Minimal research, however, has examined whether acute exercise is associated with implicit memory, which was the purpose of this study. Three separate experimental studies were computed (N = 120; Mean age = 21). In Experiment 1, participants were randomly assigned to either a moderate-intensity bout of acute exercise (15-minute) or engaged in a seated control task (15-minute), followed by the completion of a word-fragmentation implicit memory task. Experiment 2 replicated Experiment 1, but instead employed a higher-intensity exercise protocol. For Experiment 3, participants were randomly assigned to either a moderate-intensity bout of acute exercise (15-minute) or engaged in a seated control task (15-minute), followed by the completion of a real world, 3-dimensional implicit memory task. For Experiment 1, the exercise and control groups, respectively, had an implicit memory score of 7.0 (0.5) and 7.5 (0.6) (t(38) = 0.67, p = .51). For Experiment 2, the exercise and control groups, respectively, had an implicit memory score of 6.9 (1.9) and 7.8 (2.4) (t(38) = 1.27, p = .21). These findings suggest that exercise, and the intensity of exercise, does not alter implicit memory from a word fragmentation task. For Experiment 3, the exercise and control groups, respectively, had a discrimination implicit memory index score of 0.48 (0.18) and 0.29 (0.32) (t(38) = 2.16, p = .03). In conclusion, acute exercise does not influence a commonly used laboratory-based assessment of implicit memory but may enhance real world-related implicit memory function.

Older adults show less interference from task-irrelevant social categories: evidence from the garner paradigm

Though age-related difference in most cognitive performance has been found, there was no previous research examining age difference in multiple social categorizations. Using faces as stimuli and Garner Selective Attention Paradigm, this study explored the different characteristics of implicit and explicit social categorization between young and older adults. The results showed that young perceivers explicitly categorized gender and age of the faces faster and more readily than older perceivers did. When young adults judged specific category (gender category in Experiment 1; age category in Experiment 2), they were interfered from the completing irrelative category; however, irrelative category could not capture older adults' attention. These results first suggest perceivers' age indeed plays an important role in multiple social categorizations.

Replication and extension of long-term implicit memory: Perceptual priming but conceptual cessation

We endeavored to replicate Mitchell's (2006) finding of 17-year implicit memory priming. Subjects saw word and picture stimuli in 1999-2000 (M age = 18.9) and were retested after 11-14 years (M = 13.2; M age = 32.1). Via the internet, they completed four implicit memory tasks: picture fragment identification, word fragment completion, word stem completion, and category exemplar generation. Relative to control subjects (matched on stimuli, age, and education), longitudinal subjects revealed priming on picture and word fragment identification (perceptual tasks), but no priming on word stem completion or category exemplar generation (conceptual tasks). Four longitudinal subjects who failed to recall participating in the prior laboratory session had priming similar to the 10 subjects who did remember. Thus, we replicated the longevity of perceptual priming for pictures, and extended this to word fragment priming as well.

Age effects on explicit and implicit memory

It is well-documented that explicit memory (e.g., recognition) declines with age. In contrast, many argue that implicit memory (e.g., priming) is preserved in healthy aging. For example, priming on tasks such as perceptual identification is often not statistically different in groups of young and older adults. Such observations are commonly taken as evidence for distinct explicit and implicit learning/memory systems. In this article we discuss several lines of evidence that challenge this view. We describe how patterns of differential age-related decline may arise from differences in the ways in which the two forms of memory are commonly measured, and review recent research suggesting that under improved measurement methods, implicit memory is not age-invariant. Formal computational models are of considerable utility in revealing the nature of underlying systems. We report the results of applying single and multiple-systems models to data on age effects in implicit and explicit memory. Model comparison clearly favors the single-system view. Implications for the memory systems debate are discussed.

Lexical Priming in Alzheimer's Disease and Aphasia

Lexical priming was examined in patients with Alzheimer's disease and in aphasic patients. Control participants were divided into young and elderly [cf. Arroyo-Anlló et al.: Eur J Cogn Psychol 2004;16:535-553]. For lexical priming, a word-stem completion task was used. Normal elderly participants had lexical priming scores that were significantly lower than those of young individuals. Analysis of covariance with age and educational level as covariates showed that the control participants, aphasic and Alzheimer patients did not differ significantly on the lexical priming task. Our results suggest that performance in the lexical priming task diminishes with physiological aging, but is not significantly affected by mild or moderate Alzheimer's disease or by fluent or non-fluent aphasia.

Priming picture naming with a semantic task: an fMRI investigation

Prior semantic processing can enhance subsequent picture naming performance, yet the neurocognitive mechanisms underlying this effect and its longevity are unknown. This functional magnetic resonance imaging study examined whether different neurological mechanisms underlie short-term (within minutes) and long-term (within days) facilitation effects from a semantic task in healthy older adults. Both short- and long-term facilitated items were named significantly faster than unfacilitated items, with short-term items significantly faster than long-term items. Region of interest results identified decreased activity for long-term facilitated items compared to unfacilitated and short-term facilitated items in the mid-portion of the middle temporal gyrus, indicating lexical-semantic priming. Additionally, in the whole brain results, increased activity for short-term facilitated items was identified in regions previously linked to episodic memory and object recognition, including the right lingual gyrus (extending to the precuneus region) and the left inferior occipital gyrus (extending to the left fusiform region). These findings suggest that distinct neurocognitive mechanisms underlie short- and long-term facilitation of picture naming by a semantic task, with long-term effects driven by lexical-semantic priming and short-term effects by episodic memory and visual object recognition mechanisms.

The neural correlates of picture naming facilitated by auditory repetition

BACKGROUND

Overt repetition of auditorily presented words can facilitate picture naming performance in both unimpaired speakers and individuals with word retrieval difficulties, but the underlying neurocognitive mechanisms and longevity of such effects remain unclear. This study used functional magnetic resonance imaging to examine whether different neurological mechanisms underlie short-term (within minutes) and long-term (within days) facilitation effects from an auditory repetition task in healthy older adults.

RESULTS

The behavioral results showed that both short- and long-term facilitated items were named significantly faster than unfacilitated items, with short-term items significantly faster than long-term items. Neuroimaging analyses identified a repetition suppression effect for long-term facilitated items, relative to short-term facilitated and unfacilitated items, in regions known to be associated with both semantic and phonological processing. A repetition suppression effect was also observed for short-term facilitated items when compared to unfacilitated items in a region of the inferior temporal lobe linked to semantic processing and object recognition, and a repetition enhancement effect when compared to long-term facilitated items in a posterior superior temporal region associated with phonological processing.

CONCLUSIONS

These findings suggest that different neurocognitive mechanisms underlie short- and long-term facilitation of picture naming by an auditory repetition task, reflecting both phonological and semantic processing. More specifically, the brain areas engaged were consistent with the view that long-term facilitation may be driven by a strengthening of semantic-phonological connections. Short-term facilitation, however, appears to result in more efficient semantic processing and/or object recognition, possibly in conjunction with active recognition of the phonological form.