When awareness gets in the way : reactivation aversion effects resolve the generality/specificity paradox in sensorimotor interference tasks

Interference tasks combining different distractor types usually find that between-trial adaptations (congruency sequence effects [CSEs]) do not interact with each other, suggesting that sensorimotor control is domain-specific. However, within each trial, different distractor types often do interact, suggesting that control is domain-general. The present study presents a solution to this apparent paradox. In 3 experiments, testing 130 participants in total, we (a) confirm the simultaneous presence of between-trial domain-specific (noninteracting) CSEs and within-trial “domain-general” interactions in a fully factorial hybrid prime-Simon design free of repetition or contingency confounds; (b) demonstrate that the within-trial interaction occurs with supraliminal, but not with subliminal primes; and (c) show that it is disproportionately enlarged in older adults. Our findings suggest that whereas interference (priming and Simon) effects and CSEs reflect direct sensorimotor control, the within-trial interaction does not reflect sensorimotor control but “confusion” at higher-level processing stages (reactivation aversion effect [RAE])

Heart rate variability predicts older adults’ avoidance of negativity

Objectives The ability to produce situation-appropriate cognitive and emotional responses is dependent on autonomic nervous system (ANS) functionality. Heart rate variability (HRV) is an index of ANS functionality, and resting HRV levels have been associated with cognitive control and inhibitory capacity in young adults, particularly when faced with emotional information. As older adults’ greater preference for positive and avoidance of negative stimuli (positivity effect) is thought to be dependent on cognitive control, we hypothesized that HRV could predict positivity-effect magnitude in older adults. Method We measured resting-level HRV and gaze preference for happy and angry (relative to neutral) faces in 63 young and 62 older adults. Results Whereas young adults showed no consistent preference for happy or angry faces, older adults showed the expected positivity effect, which predominantly manifested as negativity avoidance rather than positivity preference. Crucially, older but not young adults showed an association between HRV and gaze preference, with higher levels of HRV being specifically associated with stronger negativity avoidance. Discussion This is the first study to demonstrate a link between older adults’ ANS functionality and their avoidance of negative information. Increasing the efficiency of the cardiovascular system might selectively improve older adults’ ability to disregard negative influences

Food for happy thought : glucose protects age-related positivity effects under cognitive load

Older adults show a preference for positive information, which disappears under high task demands. We examined whether glucose can help older adults preserve their positivity effect (PE) under high cognitive load. One hundred and twenty-two adults (40 young and 42 older in Experiment 1; 40 older in Experiment 2) consumed a glucose (25 g) or a taste-matched placebo drink and completed an immediate recall task of emotional word-lists presented under high- and low-load conditions. Older adults showed PEs for low-load lists. Whereas PEs disappeared for older-placebo participants for high-load lists, older-glucose participants retained their positive preference. Providing the brain with extra energy resources can help older adults achieve PEs even under demanding conditions

Age-related deficits in efficiency of low-level lateral inhibition

Background: In a masked prime task using a 0 ms prime-target inter-stimulus-interval, responses on trials where prime and target match (compatible trials) are usually faster and more accurate than responses where prime and target mismatch (incompatible trials). This positive compatibility effect (PCE) comprises both behavioral benefits on compatible relative to neutral trials, and behavioral costs on incompatible relative to neutral trials. Comparing performance in 2- vs. 4-alternative-response versions of the task indicates that benefits are due to direct priming (i.e., pre-activation) of a motor response, whereas costs reflect an inhibition of the alternative response tendency. The present study employs this paradigm to test the hypothesis that normal aging is associated with a selective deficit in inhibitory function, affecting both low-level motor and higher-level executive control. Experiment and Results: Testing 20 young and 20 older healthy adults, we found that (1) overall, prime-induced benefits were of similar magnitude across age groups, but inhibition-based costs were smaller in older compared to young adults; (2) increasing the number of response alternatives caused the same pattern of unaltered benefits and reduced costs in both age groups; and (3) costs, but not benefits, in the 2-alternative condition were significantly predicted by scores on the digit symbol substitution task (DSST), independently of age and other background variables. Interpretation: Results demonstrate the possibility of isolating an inhibitory component in low-level perceptuo-motor control. Importantly, this component shows an age-related decline in the absence of a corresponding decline of visuo-motor excitability, and appears to be linked to performance on a higher-level processing speed task. We hypothesize that aging might affect the brain's ability to establish precise short-term lateral inhibitory links, and that even in young adults, the efficiency of such links is a significant contributing factor in higher-level cognitive performance

Sugar rush or sugar crash?:A meta-analysis of carbohydrate effects on mood

The effect of carbohydrate (CHO) consumption on mood is at the center of a long-standing debate, with researchers reporting both mood improvements and decrements following CHO ingestion. As global consumption of sugar-sweetened products has sharply increased in recent years, examining the validity of claims of an association between CHOs and mood is of high importance. We conducted a systematic review and meta-analysis to evaluate the relationship between acute CHO ingestion and mood. We examined the time-course of CHO-mood interactions and considered the role of moderator variables potentially affecting the CHO-mood relationship. Analysis of 176 effect sizes (31 studies, 1259 participants) revealed no positive effect of CHOs on any aspect of mood at any time-point following their consumption. However, CHO administration was associated with higher levels of fatigue and less alertness compared with placebo within the first hour post-ingestion. These findings challenge the idea that CHOs can improve mood, and might be used to increase the public’s awareness of the myth of the ‘sugar rush’, inform health policies to decrease sugar consumption, and promote healthier alternatives

The negative compatibility effect: A case for self-inhibition

In masked priming, a briefly presented prime stimulus is followed by a mask, which in turn is followed by the task-relevant target. Under certain conditions, negative compatibility effects (NCNCEs) occur, with impaired performance on compatible trials (where prime and target indicate the same response) relative to incompatible trials (where they indicate opposite responses). However, the exact boundary conditions of NCEs, and hence the functional significance of this effect, are still under discussion. In particular, it has been argued that the NCE might be a stimulus-specific phenomenon of little general interest. This paper presents new findings indicating that the NCE can be obtained under a wider variety of conditions, suggesting that it reflects more general processes in motor control. In addition, evidence is provided suggesting that prime identification levels in forced choice tasks – usually employed to estimate prime visibility in masked prime tasks – are affected by prior experience with the prime (Exp. 1) as well as by direct motor priming (Exp. 2 & 3)

Look on the bright side : positivity bias modulates interference effects in the Simon Task

Negative faces are detected more quickly but categorized more slowly than positive faces. Using a Simon task, we examined stimulus- and response-related processes of this dissociation: if negative stimuli are both processed and responded to more quickly than positive ones, they should elicit reduced Simon effects. Conversely, if negative stimuli are processed more quickly but responded to more slowly, enlarged Simon effects should occur. Consistent with the first possibility, negative stimuli showed reduced Simon effects. Unexpectedly, this reduction transferred to neutral stimuli (arrows and pointing hands) requiring the same response as negative faces. This pattern suggests that spatial attention became biased toward the side associated with a positive-face response and away from the side associated with a negative-face response, demonstrating that, similar to higher level cognitive decision processes, even early attentional processes can be subject to a positivitybias (“Pollyanna effect”)

Context, not conflict, drives cognitive control

Theories of cognitive control generally assume that perceived conflict acts as a signal to engage inhibitory mechanisms that suppress subsequent conflicting information. Crucially, an absence of conflict is not regarded as being a relevant signal for cognitive control. Using a Cueing, a Priming, and a Simon task, we provide evidence that conflict does not have this unique signal status: Encountering a conflict does not lead to behavioral adjustments on subsequent conflict trials, whereas encountering a non-conflict trial does lead to behavioral adjustments on subsequent nonconflict trials. We propose that this apparent role-reversal can be explained by a mechanism that responds to both the presence and the absence of conflict, down-regulating the visuo-motor system following conflict, and up-regulating it following non-conflict

Dissociating Local and Global Levels of Perceptuo-Motor Control in Masked Priming

Masked prime stimuli presented near the threshold of conscious awareness affect responses to subsequent targets. The direction of these priming effects depends on the temporal characteristics of the prime-mask-target sequence. With short prime/mask-target intervals, benefits for compatible trials (primes and targets mapped to the same response) and costs for incompatible trials are observed. This pattern reverses with longer intervals. We argue a) that these effects reflect the initial activation and subsequent self-inhibition of the primed response, and the corresponding inhibition and subsequent disinhibition of the non-primed response, and b) that they are generated at dissociable local (within response channels) and global (between channels) levels of motor control. In two experiments, global-level priming effects were modulated by changing the number of response alternatives, whereas local-level effects remained unaffected. This suggests that low-level motor control mechanisms can be successfully decomposed into separable sub-components, operating at different levels within the motor system