Age, criterion flexibility, and associative recognition

Feasibility of measuring memory response to increasing dexmedetomidine sedation in children

BACKGROUND

The memory effect of dexmedetomidine has not been prospectively evaluated in children. We evaluated the feasibility of measuring memory and sedation responses in children during dexmedetomidine sedation for non-painful radiological imaging studies. Secondarily, we quantified changes in memory in relation to the onset of sedation.

METHODS

A 10 min bolus of dexmedetomidine (2 mcg kg^-1) was given to children as they named simple line drawings every five s. The absence of sedation was identified as any verbal response, regardless of correctness. After recovery, recognition memory was tested with correct Yes/No recognitions (50% novel pictures) and was matched to sedation responses during the bolus period (subsequent memory paradigm).

RESULTS

Of 64 accruals, 30 children (mean [SD]6.1 (1.2) yr, eight male) received dexmedetomidine and completed all study tasks. Individual responses were able to be modelled successfully in the 30 children completing all the study tasks, demonstrating feasibility of this approach. Children had 50% probability of verbal response at five min 40 s after infusion start, whereas 50% probability of subsequent recognition memory occurred sooner at four min five s.

CONCLUSIONS

Quantifying memory and sedation effects during dexmedetomidine infusion in verbal children was possible and demonstrated that memory function was present until shortly before verbal unresponsiveness occurred. This is the first study to investigate the effect of dexmedetomidine on memory in children.

CLINICAL TRIAL REGISTRATION

NCT 02354378.

Adaptive response criteria in road hazard detection among older drivers

OBJECTIVES

The majority of existing investigations on attention, aging, and driving have focused on the negative impacts of age-related declines in attention on hazard detection and driver performance. However, driving skills and behavioral compensation may accommodate for the negative effects that age-related attentional decline places on driving performance. In this study, we examined an important question that had been largely neglected in the literature linking attention, aging, and driving: can top-down factors such as behavioral compensation, specifically adaptive response criteria, accommodate the negative impacts from age-related attention declines on hazard detection during driving?

METHODS

In the experiment, we used the Drive Aware Task, a task combining the driving context with well-controlled laboratory procedures measuring attention. We compared younger (n = 16, age 21-30) and older (n = 21, age 65-79) drivers on their attentional processing of hazards in driving scenes, indexed by percentage of correct responses and reaction time of hazard detection, as well as sensitivity and response criteria using signal detection analysis.

RESULTS

Older drivers, in general, were less accurate and slower on the task than younger drivers. However, results from this experiment revealed that older, but not younger, drivers adapted their response criteria when the traffic condition changed in the driving scenes. When there was more traffic in the driving scene, older drivers became more liberal in their responses, meaning that they were more likely to report that a driving hazard was detected.

CONCLUSIONS

Older drivers adopt compensatory strategies for hazard detection during driving. Our findings showed that, in the driving context, even at an older age our attentional functions are still adaptive according to environmental conditions. This leads to considerations on potential training methods to promote adaptive strategies that may help older drivers maintain performance in road hazard detection.

They can take a hint: Older adults effectively integrate memory cues during recognition

Adaptively biasing recognition judgments in light of environmental cues improves net accuracy. Based on previous work suggesting that strategically shifting biases on a trial-wise basis should be cognitively demanding, the authors predicted that older adults would not achieve the same accuracy benefits from environmental cues as the young. However, despite showing clear declines in cognitive control as indexed by complex span, older adults demonstrated similar accuracy gains and similar alterations of response probabilities with cues of 75% reliability (Experiment 1) and more complex cues spanning 3 levels of reliability (Experiment 2). Despite preserved gains in accuracy, older adults clearly demonstrated disproportionate slowing that was specific to trials in which cues were invalid. This slowing may reflect impairments in behavioral inhibition that could impinge upon accuracy were responding increasingly sped and future work manipulating response speed and measures of inhibition may yield further insights.

Age Effects in Adaptive Criterion Learning

OBJECTIVE

Although prior work has examined age-related changes to criterion placement and flexibility, no study tested these constructs through a paradigm that employs adaptive feedback to encourage specific criterion changes. The goal of this study was to assess age differences in how young and older adults adapt and shift criteria in recognition memory decisions based on trial-by-trial feedback.

METHOD

Young and older adults completed an adaptive criterion learning paradigm. Over 3 study/test cycles, a biased feedback technique at test encouraged more liberal or strict responding by false-positive feedback toward false alarms or misses.

RESULTS

Older adults were more conservative than young, even when feedback first encouraged a liberal response bias, and older adults adaptively placed criteria in response to biased feedback, much like young adults. After first being encouraged to respond conservatively, older adults shifted criteria less than young when feedback encouraged more lenient responding.

DISCUSSION

These findings evidence labile adaptive criteria placement and criteria shifting with age. However, age-related tendencies toward conservative response biases may limit the extent to which criteria can be shifted in a lenient direction.

The impact of beliefs about face recognition ability on memory retrieval processes in young and older adults

This study examined whether beliefs about face recognition ability differentially influence memory retrieval in older compared to young adults. Participants evaluated their ability to recognise faces and were also given information about their ability to perceive and recognise faces. The information was ostensibly based on an objective measure of their ability, but in actuality, participants had been randomly assigned the information they received (high ability, low ability or no information control). Following this information, face recognition accuracy for a set of previously studied faces was measured using a remember-know memory paradigm. Older adults rated their ability to recognise faces as poorer compared to young adults. Additionally, negative information about face recognition ability improved only older adults' ability to recognise a previously seen face. Older adults were also found to engage in more familiarity than item-specific processing than young adults, but information about their face recognition ability did not affect face processing style. The role that older adults' memory beliefs have in the meta-cognitive strategies they employ is discussed.

Age and response bias: Evidence from the strength-based mirror effect

Performance in episodic memory is determined both by accurate retrieval from memory and by decision processes. A substantial body of literature suggests slightly poorer episodic memory accuracy for older than younger adults; however, age-related changes in the decision mechanisms in memory have received much less attention. Response bias, the willingness to endorse an item as remembered, is an important decision factor that contributes to episodic memory performance, and therefore understanding age-related changes in response bias is critical to theoretical development. We manipulate list strength in order to investigate two aspects of response bias. First, we evaluate whether criterion placement in episodic memory differs for older and younger adults. Second, we ask whether older adults have the same degree of flexibility to adjust the criterion in response to task demands as younger adults. Participants were tested on weakly and strongly encoded lists where word frequency (Experiment 1) or similarity between targets and foils (Experiment 2) was manipulated. Both older and younger adults had higher hit rates and lower false-alarm rates for strong lists than for weak lists (i.e., a strength-based mirror effect). Older adults were more conservative (less likely to endorse an item as studied) than younger adults, and we found no evidence that older and younger adults differ in their ability to flexibly adjust their criterion based on the demands of the task.