Identity-based inhibitory processing during focused attention

Flexible processing of distractor stimuli under stress

Acute stress is assumed to affect executive processing of stimulus information, although extant studies have yielded heterogeneous findings. The temporal flanker task, in which a target stimulus is preceded by a distractor of varying utility, offers a means of investigating various components involved in the adjustment of information processing and conflict control. Both behavioral and EEG data obtained with this task suggest stronger distractor-related response activation in conditions associated with higher predictivity of the distractor for the upcoming target. In two experiments we investigated distractor-related processing and conflict control after inducing acute stress (Trier Social Stress Test). Although the stressed groups did not differ significantly from unstressed control groups concerning behavioral markers of attentional adjustment (i.e., Proportion Congruent Effect), or event-related sensory components in the EEG (i.e., posterior P1 and N1), the lateralized readiness potential demonstrated reduced activation evoked by (predictive) distractor information under stress. Our results suggest flexible adjustment of attention under stress but hint at decreased usage of nominally irrelevant stimulus information for biasing response selection.

Age differences in inhibitory and working memory functioning: limited evidence of system interactions

Debate persists regarding the nature of age-related deficits in inhibition, and whether inhibitory functioning depends on working memory systems. The current research aimed to measure age-related differences in inhibition and working memory, characterize the relationship between inhibitory functions and working memory performance, and determine how these relationships are affected by age. Toward these ends, we measured performance on a range of established paradigms in 60 young adults (18-30 years) and 60 older adults (60-88 years). Our findings support age-related increases in reflexive inhibition (based on the fixation offset effect and inhibition of return) and age-related decrements in volitional inhibition (based on several paradigms: antisaccade, Stroop, flanker, and Simon). This evidence of stronger reflexive inhibition combined with weaker volitional inhibition suggests that age-related deterioration of cortical structures may allow subcortical structures to operate less controlled. Regarding working memory, older adults had lower backward digit scores and lower forward and backward spatial scores. However, of the 32 analyses (16 in each age group) that tested for dependence of inhibitory functioning on working memory functioning, only one (in young adults) indicated that inhibition performance significantly depended on working memory performance. These results indicate that inhibition and working memory function largely independently in both age groups, and age-related working memory difficulties cannot account for age-related declines in inhibitory control.

Chronic exercise and neuropsychological function in healthy young adults: a randomised controlled trial investigating a running intervention

Despite the well-known physical and mental health benefits of regular exercise, many of the world's population, including healthy young adults, grossly undershoot recommended physical activity levels. Chronic exercise has potential to improve cognitive performance and affect in most age groups. However, there is currently a poverty of relevant research in young adults, especially randomised controlled trials. To address this, the current research investigated the effects of a running intervention on neuropsychological function (cognition and affect) in young adults. We predicted that following a running intervention, neuropsychological performance would improve alongside increases in aerobic fitness. Thirty-two healthy young adult university students were randomised (using a 3:1 ratio) into an intervention or control group, with the intervention group (n = 24) asked to run for 30 min three times a week over a 6-week period and the control group (n = 8) asked to maintain their current level of exercise over a 6-week period. We assessed fitness, cognitive performance, affect and running enjoyment at baseline and follow-up, and runners recorded the environmental conditions of their runs. Repeated measures ANCOVAs failed to find any significant effects of the running intervention on fitness or the neuropsychological measures. Anecdotal evidence supported running environment and enjoyment as potentially relevant factors. The failure to find any fitness improvements, which likely underpins the lack of neuropsychological improvements, highlights the importance of monitoring exercise sessions. Coupled with other insights gained from this trial, this article may prove useful towards future endeavours to develop exercise interventions beneficial to young adults.TRN: ACTRN12621000242820, Date of registration: 08/03/2021.

Attentional adjustment in priming tasks: control strategies depend on context

Goal-directed behavior is assumed to require processes of attentional biasing to counter unwanted action tendencies elicited by distracting stimulus information. This is particularly so if stimulus categories that define the target and the distractor frequently reverse, requiring participants to respond to previously ignored stimulus categories and vice versa. In the current study, we investigated control strategies under such conditions. Specifically, we assessed trial-to-trial modulation of distractor-interference (i.e., congruency sequence effect, CSE) in a temporal flanker task associated with repetition versus alternation of the assignment of stimulus category (i.e., digits, letters) to targets and distractors (i.e., the character presented second or first, respectively) under conditions of a long SOA of 1000 ms (Experiment 1A) and 1200 ms (Experiment 1B). Whereas previous research, using a shorter SOA, suggested temporal-order control (i.e., the occurrence of a CSE in both repetition and-albeit less pronounced-alternation trials), lengthening the distractor-target SOA resulted in a CSE confined to repetition trials, suggesting strong or exclusive reliance on stimulus categories for attentional control (Experiment 1A and B). Adding a redundant stimulus feature (i.e., color), discriminating targets and distractors, eliminated the difference of CSE patterns in repetition and alternation trials (Experiment 2). Together, our results suggest that the strength of concurrently applied control strategies or the choice of a particular control strategy depend on contextual factors.

Behavioral and Neural Changes Induced by a Blended Essential Oil on Human Selective Attention

Selective attention refers to the selecting and preferential processing of specific information while simultaneously suppressing irrelevant distractors, activities linked to various cognitive skills and academic achievements. The influence of essential oils on the cognition of humans has been extensively explored. However, the effects of essential oils on human selective attention and the underlying neural mechanisms remain unclear. In the present study, participants were divided into a “blended essential oil” group and a “no essential oil” group and enrolled on a negative priming task, including a control condition and a negative priming condition. The event-related potential technique was used to examine the brain mechanisms underlying the blended essential oil effects on human selective attention. Behavioral results showed that individuals responded more quickly in the negative priming condition when exposed to the blended essential oil. In addition, the blended essential oil eliminated the differences in the P300 amplitude in the postcentral area of the brain between the negative priming condition and the control condition. Moreover, the blended essential oil led to stronger functional connectivity during the task. The present study thus suggests that blended essential oil can significantly change brain activity and functional connections in human beings, which may improve human selective attention.

Independent control processes? Evidence for concurrent distractor inhibition and attentional usage of distractor information

Interference evoked by a distractor presented prior to a target stimulus is reduced when the distractor-target SOA is increased, suggesting inhibition of distractor-related activation. Distractor processing is also assumed to be (strategically) adjusted to the proportions of congruent and incongruent target-distractor combinations, yielding a larger distractor interference effect when the proportion of congruent trials is higher (i.e., Proportion Congruent Effect, PCE). To explore the interplay of proportion congruent-based processing adjustment and the time course of distractor-related activation we varied the proportions of congruent and incongruent trials as well as the distractor-target SOA. To control for item-specific priming we kept distractor-related contingencies (i.e., frequency of individual distractor-target conjunctions) constant for a subset of the stimuli (and used a different subset to manipulate the proportions of congruent and incongruent trials). A PCE occurred, even for the subset of stimuli associated with constant distractor-related contingencies, thus ruling out item-specific contingency learning. Distractor interference was reduced when the SOA was increased, but this reduction did not differ between the proportion congruent conditions, as confirmed by a Bayesian analysis. Our results are consistent with independent processes pertaining to usage of distractor information for biasing response selection and distractor inhibition during the SOA. Alternative interpretations of the independent effects of the PC manipulation and the distractor-target SOA are discussed.

Volunteering in the Community: Potential Benefits for Cognitive Aging

Objectives

This review aims to advance understanding of the potential benefits of volunteering in the community for older adults' cognitive functioning by taking an in-depth look at the relevant evidence to date.

Method

This review describes the main pathways through which volunteering could plausibly benefit cognitive functioning and critically examines research that has specifically investigated links between volunteering and cognition. Fifteen articles that assessed in adults aged ≥ 55 years the relationship between volunteering (predictor) and cognitive functioning (outcome) were identified via literature database searches.

Results

On balance, evidence from the small number of relevant studies to date supports the idea that volunteering can protect against cognitive aging with respect to global functioning and at least some specific cognitive domains. Studies that used robust designs and assessed domain-specific cognitive functioning produced the largest effect sizes.

Discussion

To help advance the field, this review puts forward recommendations for future research, with an emphasis on the need for robust study designs and specific investigations into the nature and extent of the cognitive benefits of volunteering. Through that work, researchers can determine how a simple and accessible activity like volunteering can best be used to help reduce the burden of age-related cognitive decline.

Conflict resolution in the Eriksen flanker task: Similarities and differences to the Simon task

In the Eriksen flanker task as well as in the Simon task irrelevant activation produces a response conflict that has to be resolved by mental control mechanisms. Despite these similarities, however, the tasks differ with respect to their delta functions, which express how the congruency effects develop with response time. The slope of the delta function is mostly positive for the flanker task, but negative for the Simon task. Much effort has been spent to explain this difference and to investigate whether it results from task-specific control. A prominent account is that the temporal overlap between irrelevant and relevant response activation is larger in the flanker task than in the Simon task. To test this hypothesis, we increased the temporal distance in a flanker task by presenting the flankers ahead of the target. This not only produced negatively sloped delta functions but also caused reversed congruency effects. We also conducted a Simon-task experiment in which we varied the proportion of congruent stimuli. As a result, the delta function was negatively sloped only if the proportion was low. These results demonstrate that a long temporal distance is necessary but not sufficient for observing negatively sloped delta functions. Finally, we modeled the data with drift-diffusion models. Together, our results show that differently sloped delta functions can be produced with both tasks. They further indicate that activation suppression is an important control mechanism that can be adapted rather flexibly to the control demands.

The time course of distractor-based response activation with predictable and unpredictable target onset

Electrophysiological recording in a temporal flanker task (i.e., distractors preceding the targets) has demonstrated that distractor processing is adjusted to the overall utility of the distractors. Under high utility, that is, distractors are predictive of the target/response, distractors immediately activate the corresponding response (as indicated by the lateralized readiness potential, LRP). This activation has been shown to be markedly postponed when the target predictably occurs delayed. To investigate the occurrence and time course of distractor-related response activation under conditions of unpredictable target onset, we randomly varied the stimulus-onset asynchrony (SOA) between distractors and targets and recorded the distractor-evoked LRP. When the distractor utility was high, an LRP occurred shortly after distractor presentation. In case of a long SOA the time course of this LRP was characterized by a drop back to baseline and a subsequent re-activation that reached a substantial level before target onset. These results suggest that distractor processing is characterized by sophisticated adjustments to experienced utility and temporal constraints of the task as well as by further control processes that regulate premature response activation.

Response priming with motion primes: negative compatibility or congruency effects, even in free-choice trials

How actions are chosen, and what they are influenced by, has been the focus of several research traditions. Influences on actions are often studied using compatibility paradigms, such as response priming. Here, a first stimulus (i.e., the prime) is presented shortly before a second stimulus (i.e., the target) which has to be classified. Reaction times to the target are often reduced when primes and targets are compatible compared to incompatible primes and targets-i.e., a positive compatibility effect (PCE). There are, however, some conditions in which reliably negative compatibility effects (NCEs), with faster reactions to incompatible targets, are found. Actions in real life are often influenced by perceived motion and are less determined by following (target) stimuli as it is the case in typical response priming studies with predetermined stimulus-response mappings. Thus, in the current experiment we used motion primes in forced-choice trials (with >> and << as targets) as well as in free-choice trials (with <> and >< as targets). Essentially, we found PCEs in the short-SOA condition and NCEs in the long-SOA condition. The pattern was not qualified by task (i.e., forced choice/free choice). The results provide evidence that NCEs with motion primes are found even without strong links between target stimuli and responses and that especially PCEs can be found with simpler and smaller targets than have been used in previous experiments.

Moving Single Dots as Primes for Static Arrow Targets

In response priming, responses are typically faster and more accurate if the prime calls for the same response as the target (i.e., compatible trials) than when primes and targets trigger different responses (i.e., incompatible trials). With moving rows-of-dots as primes for static arrow targets, participants instead responded faster to incompatible targets with longer SOAs (stimulus onset asynchrony, > 200 ms). Until now, it is unclear whether this effect is specific to the material. In the present research, a single moving dot was used as a prime. Further, we analyzed compatibility effects depending on reaction times (RTs). Positive compatibility effects in reaction times were found with an SOA of 147 ms and even with a relatively long SOA of 360 ms; for very long SOAs (800-1,200 ms), negative effects were found. We interpreted this as evidence that the specific type of motion is irrelevant for the occurrence of a negative compatibility effect.

Altered inhibitory control and increased sensitivity to cross-modal interference in tinnitus during auditory and visual tasks

Tinnitus is the perception of sound in the absence of external stimulus. Currently, the pathophysiology of tinnitus is not fully understood, but recent studies indicate that alterations in the brain involve non-auditory areas, including the prefrontal cortex. In experiment 1, we used a go/no-go paradigm to evaluate the target detection speed and the inhibitory control in tinnitus participants (TP) and control subjects (CS), both in unimodal and bimodal conditions in the auditory and visual modalities. We also tested whether the sound frequency used for target and distractors affected the performance. We observed that TP were slower and made more false alarms than CS in all unimodal auditory conditions. TP were also slower than CS in the bimodal conditions. In addition, when comparing the response times in bimodal and auditory unimodal conditions, the expected gain in bimodal conditions was present in CS, but not in TP when tinnitus-matched frequency sounds were used as targets. In experiment 2, we tested the sensitivity to cross-modal interference in TP during auditory and visual go/no-go tasks where each stimulus was preceded by an irrelevant pre-stimulus in the untested modality (e.g. high frequency auditory pre-stimulus in visual no/no-go condition). We observed that TP had longer response times than CS and made more false alarms in all conditions. In addition, the highest false alarm rate occurred in TP when tinnitus-matched/high frequency sounds were used as pre-stimulus. We conclude that the inhibitory control is altered in TP and that TP are abnormally sensitive to cross-modal interference, reflecting difficulties to ignore irrelevant stimuli. The fact that the strongest interference effect was caused by tinnitus-like auditory stimulation is consistent with the hypothesis according to which such stimulations generate emotional responses that affect cognitive processing in TP. We postulate that executive functions deficits play a key-role in the perception and maintenance of tinnitus.

Auditory conflict resolution correlates with medial-lateral frontal theta/alpha phase synchrony

When multiple persons speak simultaneously, it may be difficult for the listener to direct attention to correct sound objects among conflicting ones. This could occur, for example, in an emergency situation in which one hears conflicting instructions and the loudest, instead of the wisest, voice prevails. Here, we used cortically-constrained oscillatory MEG/EEG estimates to examine how different brain regions, including caudal anterior cingulate (cACC) and dorsolateral prefrontal cortices (DLPFC), work together to resolve these kinds of auditory conflicts. During an auditory flanker interference task, subjects were presented with sound patterns consisting of three different voices, from three different directions (45° left, straight ahead, 45° right), sounding out either the letters “A” or “O”. They were asked to discriminate which sound was presented centrally and ignore the flanking distracters that were phonetically either congruent (50%) or incongruent (50%) with the target. Our cortical MEG/EEG oscillatory estimates demonstrated a direct relationship between performance and brain activity, showing that efficient conflict resolution, as measured with reduced conflict-induced RT lags, is predicted by theta/alpha phase coupling between cACC and right lateral frontal cortex regions intersecting the right frontal eye fields (FEF) and DLPFC, as well as by increased pre-stimulus gamma (60–110 Hz) power in the left inferior fontal cortex. Notably, cACC connectivity patterns that correlated with behavioral conflict-resolution measures were found during both the pre-stimulus and the pre-response periods. Our data provide evidence that, instead of being only transiently activated upon conflict detection, cACC is involved in sustained engagement of attentional resources required for effective sound object selection performance.

Inhibitory mechanisms in single negative priming from ignored and briefly flashed primes: the key role of the inter-stimulus interval

The influence of interstimulus intervals (ISIs) on priming effects was investigated using a single-prime negative priming (NP) paradigm. In all experiments, a brief (16ms), centrally displayed prime (a Chinese character, to be ignored) appeared, followed by a pattern mask and then a centrally displayed target (another semantically related or unrelated Chinese character); the task required semantic categorization (animate/inanimate) of the target. An ISI could occur either between prime and mask (Experiments 1 and 5) or between mask and target (Experiments 2-4). The results revealed NP when a 470ms ISI occurred between prime and mask (Experiments 1 and 5) and when a 700ms ISI occurred between mask and target (Experiments 3 and 4). In contrast, when a long prime-target SOA was maintained but the mask-target ISI was shortened, NP disappeared (Experiment 4). The results indicated that a persisting mask/distractor (without ISI) located in the same position as the following target interfered with the buildup of inhibition, but an ISI between prime and mask or mask and target eliminated this interference, and that inhibition processes induced by an ignore instruction were implemented faster with an ISI placed between prime and mask than with an ISI placed between mask and target.

Evidence inhibition responds reactively to the salience of distracting information during focused attention

Along with target amplification, distractor inhibition is regarded as a major contributor to selective attention. Some theories suggest that the strength of inhibitory processing is proportional to the salience of the distractor (i.e., inhibition reacts to the distractor intensity). Other theories suggest that the strength of inhibitory processing does not depend on the salience of the distractor (i.e., inhibition does not react to the distractor intensity). The present study aimed to elucidate the relationship between the intensity of a distractor and its subsequent inhibition during focused attention. A flanker task with a variable distractor-target stimulus-onset asynchrony (SOA) was used to measure both distractor interference and distractor inhibition. We manipulated the intensity of the distractor in two separate ways, by varying its distance from the target (Experiment 1) and by varying its brightness (Experiment 2). The results indicate that more intense distractors were associated with both increased interference and stronger distractor inhibition. The latter outcome provides novel support for the reactive inhibition hypothesis, which posits that inhibition reacts to the strength of distractor input, such that more salient distractors elicit stronger inhibition.