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Biomedical subjects

Fergus I M Craik

Publications and source records attributed to Fergus I M Craik.

At least 19 recordsLinked to original sources

Bilingualism as a protection against the onset of symptoms of dementia.

This study examined the effect of lifelong bilingualism on maintaining cognitive functioning and delaying the onset of symptoms of dementia in old age. The sample was selected from the records of 228 patients referred to a Memory Clinic with cognitive complaints. The final sample consisted of 184 patients diagnosed with dementia, 51% of whom were bilingual. The bilinguals showed symptoms of dementia 4 years later than monolinguals, all other measures being equivalent. Additionally, the rate of decline in Mini-Mental State Examination (MMSE) scores over the 4 years subsequent to the diagnosis was the same for a subset of patients in the two groups, suggesting a shift in onset age with no change in rate of progression.

Age of Onset↗

Brain-behavior relations across the lifespan: a commentary.

This final article provides an overview and commentary on some of the methods, findings and interpretations discussed in the preceding papers. Some major commonalities among them are highlighted and possible questions for future research projects are suggested. Topics discussed include plasticity, compensation and dedifferentiation, representation and control, memory and learning-all considered under the general heading of brain-behavior relations, and how they change across the lifespan.

Age Factors↗

The mnemonic mechanisms of errorless learning.

Errorless learning enhances memory relative to errorful, trial-and-error learning, but the extent to which this advantage relies on implicit or explicit memory processes is not clear. Previous attempts to determine the mnemonic mechanisms of errorless learning have relied on contrasts between patient groups or between tasks, but both approaches are problematic. In this study, healthy younger and older adults were engaged in errorless or errorful learning using a process dissociation procedure that provides separate estimates of explicit recollection and implicit familiarity within-subjects and within-task (Hay & Jacoby, 1996). Consistent with much prior research, we found an age-related decrement in recollection, but age-invariance in familiarity. In the young adults, errorless learning reduced the misleading familiarity of prior errors, but this benefit was offset by the non-elaborative nature of the errorless learning condition that also reduced recollection. In the older adults, who are less able to oppose familiarity-based errors because of their lower recollection, errorless learning only reduced the misleading impact of previous errors. Our results support Baddeley and Wilson's (1994) position that the errorless learning effect is mediated by implicit memory processes: individuals with reduced explicit memory benefit from errorless learning because errorless learning bypasses the need to engage explicit error elimination processes. We do not recommend standard errorless learning for individuals with intact explicit memory, such as students trying to learn information in preparation for an examination.

Adolescent↗

Cognition through the lifespan: mechanisms of change.

Cognitive abilities rise steeply from infancy to young adulthood and then are either maintained or decline to old age, depending on the specific ability. This pattern suggests corresponding continuities of mechanism and process, but it is striking that the fields of cognitive development and cognitive aging make little contact with each other's methods and theories. In this review we examine reasons for this cultural separation, and show how recent findings from both areas fit a framework couched in terms of cognitive representation and control. These two broad factors have very different lifespan trajectories; consideration of their relative growth and decline makes it clear that cognitive aging is not simply 'development in reverse'. This framework is offered in light of recent interest in finding greater continuity throughout the lifespan and creating a more comprehensive explanation of cognitive function and cognitive change.

Aging↗

Executive control in a modified antisaccade task: Effects of aging and bilingualism.

Two studies are reported that assess differences associated with aging and bilingualism in an executive control task. Previous work has suggested that bilinguals have an advantage over monolinguals in nonlinguistic tasks involving executive control; the major purpose of the present article is to ascertain which aspects of control are sensitive to the bilingual experience. Study 1 used an antisaccade task and found no effects of aging or bilingualism. Study 2 used the identical visual display but coupled to keypress responses. The results showed that bilinguals resolved various types of response conflict faster than monolinguals and that this bilingual advantage generally increased with age. A speculative interpretation of this pattern of results is offered in conclusion.

Adult↗

Dual-modality monitoring in a classification task: the effects of bilingualism and ageing.

Two experiments are reported in which monolingual and bilingual participants who were younger (Experiment 1) or older (Experiment 2) adults performed in a dual-task classification paradigm. Visually (primary task) and auditorily (secondary task) presented stimuli were classified into two categories. The stimuli belonged to two domains, letters or numbers (LN) and animals or musical instruments (AM), and the two task modalities used stimuli from the same (related) or opposite (unrelated) domains. For both age groups, bilinguals were less disrupted than monolinguals in visual sorting in the LN domain, and relatedness affected performance only in the AM domain. The results indicate different processing demands for the two domains, with the simpler domain (LN) favouring bilinguals and the more semantically complex domain (AM) favouring related judgements for the two task modalities.

Acoustic Stimulation↗

Name and face learning in older adults: effects of level of processing, self-generation, and intention to learn.

Many older adults are interested in strategies to help them learn new names. We examined the learning conditions that provide maximal benefit to name and face learning. In Experiment 1, consistent with levels-of-processing theory, name recall and recognition by 20 younger and 20 older adults was poorest with physical processing, intermediate with phonemic processing, and best with semantic processing. In Experiment 2, name and face learning in 20 younger and 20 older adults was maximized with semantic processing of names and physical processing of faces. Experiment 3 showed a benefit of self-generation and of intentional learning of name-face pairs in 24 older adults. Findings suggest that memory interventions should emphasize processing names semantically, processing faces physically, self-generating this information, and keeping in mind that memory for the names will be needed in the future.

Adult↗

Task-related activity in prefrontal cortex and its relation to recognition memory performance in young and old adults.

Older adults often have more widespread prefrontal cortex (PFC) activation during memory retrieval tasks, compared to young adults, particularly in the left hemisphere. Recruitment of additional frontal activity in older adults has been attributed by some researchers to compensation, perhaps for reduced activity elsewhere in the brain, whereas others have described it as a non-selective response that may be due to a failure to inhibit these PFC regions. To address further the impact of PFC activity on memory in older adults, we used PET to measure brain activity during recognition memory tasks. Both young and old adults showed increased activity during recognition, compared to a control task, in bilateral PFC. Young adults showed greater activation of left hippocampus and lateral temporal cortex during recognition, whereas older adults showed greater activity in the right inferior frontal gyrus. Age differences also were seen in correlations between brain activity and memory performance. There were positive correlations between activity in the right parahippocampal gyrus and recognition performance in young adults, whereas positive correlations between activity in PFC and performance were found only in older adults. These positive correlations included the right inferior PFC region where older adults had greater activation. Activity in this right PFC region was negatively correlated with medial temporal activity in both groups. These results provide further evidence for age-specific patterns of brain activity underlying memory performance and are consistent with the idea that PFC assumes a larger role in supporting successful recognition memory with increasing age. The negative correlation between activity in PFC and medial temporal regions, as well as the age differences in how these regions were related to behavior, suggest that those older individuals who recruit PFC to a greater degree may do so as a compensatory response to reductions in medial temporal regions.

Adult↗

Effect of bilingualism on cognitive control in the Simon task: evidence from MEG.

The present study used magneto-encephalography (MEG) to determine the neural correlates of the bilingual advantage previously reported for behavioral measures in conflict tasks. Bilingual Cantonese-English, bilingual French-English, and monolingual English speakers, performed the Simon task in the MEG. Reaction times were faster for congruent than for incongruent trials, and the Cantonese group was faster than the other two groups, which did not differ from each other. Analyses of the MEG data using synthetic aperture magnetometry (SAM) and partial last squares (PLS) showed that the same pattern of activity, involving signal changes in left and medial prefrontal areas, characterized all three groups. Correlations between activated regions and reaction times, however, showed that the two bilingual groups demonstrated faster reaction times with greater activity in superior and middle temporal, cingulate, and superior and inferior frontal regions, largely in the left hemisphere. The monolinguals demonstrated faster reaction times with activation in middle frontal regions. The interpretation is that the management of two language systems led to systematic changes in frontal executive functions.

Adult↗

Divided attention in younger and older adults: effects of strategy and relatedness on memory performance and secondary task costs.

Divided attention at encoding leads to a significant decline in memory performance, whereas divided attention during retrieval has relatively little effect; nevertheless, retrieval carries significant secondary task costs, especially for older adults. The authors further investigated the effects of divided attention in younger and older adults by using a cued-recall task and by measuring retrieval accuracy, retrieval latency, and the temporal distribution of attentional costs at encoding and retrieval. An age-related memory deficit was reduced by pair relatedness, whereas strategy instructions benefited both age groups equally. Attentional costs were greater for retrieval than for encoding, especially for older adults. These findings are interpreted in light of notions of an age-related associative deficit (M. Naveh-Benjamin, 2000) and age-related differences in the use of self-initiated activities and environmental support (F. I. M. Craik, 1983, 1986).

Adult↗

Memory for proper names in old age: a disproportionate impairment?

A common complaint of older adults is that they have trouble remembering names, even the names of people they know well. Two experiments examining this problem are reported in the present article. Experiment I tested episodic memory for surnames and occupations; older adults and younger adults under divided attention performed less well than did full attention younger adults, but showed no disproportionate loss of name information. Experiment 2 examined the ability to name photographs of public figures and of uncommon objects; this experiment therefore tested retrieval from semantic memory. In this case adults in their 70s did show an impairment in recall of names of known people, but not of known objects. Further analyses revealed systematic relations between naming, recognition, and rated familiarity of the categories used. Familiarity largely determined the proportions of recognizable items that were named in a prior phase. Overall, little evidence was found for a disproportionate age-related impairment in naming in either episodic or semantic memory.

Adult↗

Bilingualism, aging, and cognitive control: evidence from the Simon task.

Previous work has shown that bilingualism is associated with more effective controlled processing in children; the assumption is that the constant management of 2 competing languages enhances executive functions (E. Bialystok, 2001). The present research attempted to determine whether this bilingual advantage persists for adults and whether bilingualism attenuates the negative effects of aging on cognitive control in older adults. Three studies are reported that compared the performance of monolingual and bilingual middle-aged and older adults on the Simon task. Bilingualism was associated with smaller Simon effect costs for both age groups; bilingual participants also responded more rapidly to conditions that placed greater demands on working memory. In all cases the bilingual advantage was greater for older participants. It appears, therefore, that controlled processing is carried out more effectively by bilinguals and that bilingualism helps to offset age-related losses in certain executive processes.

Adult↗

Age-related differences in the functional connectivity of the hippocampus during memory encoding.

The purpose of the current experiment was to examine the functional connectivity of the hippocampus during encoding in young and old adults, and the way in which this connectivity was related to recognition performance. Functional connectivity was defined as the correlation between activity in the hippocampus and activity in the rest of the brain, as measured by neuroimaging. During encoding of words and pictures of objects in young adults, hippocampal activity was correlated with activity in the ventral prefrontal and extrastriate regions, and increased activity in all these regions was associated with better recognition. In contrast, older adults showed correlations between hippocampal activity and the dorsolateral prefrontal and parietal regions, and positive correlations between activity in these regions and better memory performance. This ventral/dorsal distinction suggests a shift in the cognitive resources used with age from more perceptually based processes to those involved in executive and organizational functions. The results of this study provide evidence that aging is associated with alterations in hippocampal function, including how it is functionally connected with prefrontal cortex, and that these alterations have an impact on memory performance.

Adult↗

The effects of aging and divided attention on memory for item and associative information.

The present study examined how aging and divided attention influence memory for item and associative information. Older adults and younger adults working under full-attention conditions and younger adults working under divided-attention conditions studied unrelated word pairs. Memory for item information was measured by later recognition of the 2nd word in the pair, and associative information was measured by recognition of the entire pair. Both older adults in the full-attention condition and younger adults in the divided-attention condition performed more poorly than younger adults in the full-attention condition, with the deficit in associative information being greater than the deficit in item information. In addition, a differentially greater associative decrement was found for the older adults, as shown by their heightened tendency to make false-alarm responses to re-paired (conjunction) distractors. The results are discussed in terms of an age-related reduction in processing resources compounded by an age-related increase in older adults' reliance on familiarity in associative recognition memory.

Adult↗

The role of spatial working memory in inhibition of return: evidence from divided attention tasks.

Inhibition of return (IOR) refers to a bias against returning attention to a location that has been recently attended. In the present experiments, we examined the role of working memory in IOR by introducing secondary tasks (in the temporal interval between the cue and the target) that involved a working memory component. When the secondary task was nonspatial in nature (monitoring odd digits or adding digits), IOR was present, although overall reaction times were greater in the presence of the secondary task. When the task involved a spatial working memory load (remembering the directionality of arrows or the orientation of objects), IOR was eliminated. However, when the participants had incentive to process the directionality of an arrow but did not have to use any memory system, IOR persisted at peripheral locations. Overall, the results suggest that IOR is partially mediated by a spatial working memory system.

Attention↗

Lapses of intention and performance variability reveal age-related increases in fluctuations of executive control.

We examine the hypothesis that the efficiency of executive control processes is less stable over time in older than younger adults. An age-related decrease in the efficiency of executive control should result in an increase in performance variability in task conditions requiring the recruitment of executive control processes and not in task conditions requiring minimal involvement of executive control. Performance variability was similar for younger and older adults in task conditions requiring minimal executive control and greater for older than younger adults in task conditions requiring executive control. These and other data are consistent with the proposal that aging is associated with a decrease in the stability of executive control over time.

Adult↗

Effects of divided attention on episodic memory in chronic traumatic brain injury: a function of severity and strategy.

Eleven patients with mild traumatic brain injury (MTBI) and 13 patients with moderate-to-severe TBI (STBI) were compared to 10 matched controls on episodic memory for pictorial scene-object associations (e.g. kitchen-bread) and a range of standardized neuropsychological tests of memory and frontal-lobe functions. We tested the hypothesis that deficits in episodic memory result from impaired attentional resources and/or strategic control by manipulating attentional load at encoding (focused versus divided attention) and environmental support at retrieval (free recall and recalled cued by scene versus recognition of object and scene). Patients with TBI were disproportionately affected by the divided attention manipulation, but this effect was modulated by injury severity and encoding strategy. Overall, MTBI patients were impaired only when items were encoded under divided attention, indicating memory deficits that were secondary to deficits in the executive control. STBI patients could be differentiated into two distinct functional subgroups based on whether they favored a strategy of attending to the encoding or digit-monitoring task. The subgroup favoring the digit-monitoring task demonstrated deficits in the focused attention condition, and disproportionate memory deficits in the divided attention condition. In contrast, the subgroup favoring the encoding task demonstrated intact performance across all memory measures, regardless of attentional load, and despite remarkable similarity to the other STBI subgroup on demographic, neuropsychological, and acute injury severity measures. We discuss these outcome differences in terms of the relationship between strategy and executive control and highlight the need for more sensitive anatomical and behavioral measurement at both acute and chronic stages of injury.

Adult↗

Effects of time of day on age differences in working memory.

This study investigated the hypothesis that the influence of time of day on the efficiency of working memory is greater for older than younger adults. Groups of younger and older adults performed a working memory task on 4 consecutive days, twice in the morning and twice in the evening. Objective (body temperature) and subjective (alertness ratings) measures of arousal were taken during each session. Temperature increased across the day equally for younger and older adults, whereas alertness ratings were higher in the morning for older adults and in the evening for younger adults. The efficiency of the access and deletion functions paralleled the subjective alertness rating for younger and older adults, and age-related differences in these functions were greater when individuals were tested at nonoptimal times of day. The efficiency of the response inhibition function was similar for younger and older adults and paralleled changes in body temperature.

Adult↗