Impact of working memory capacity on predominance of parietal over frontal P300 amplitude

Working memory-related neural activity varies with task load, and these neural variations can be constrained by working memory capacity (WMC). For instance, some studies suggest that parietal and frontal P300 amplitudes, reflecting working memory functioning, vary differentially with task load and WMC. The present study explored whether the predominance of parietal over frontal P300 amplitude is related to WMC, and whether this relationship varies according to task load. Thirty-one adults aged 20-40 years performed a Sternberg task with two set sizes (2 vs. 6 items), during which event-related potentials were recorded. This allowed us to explore the P300 and estimate the magnitude of its parietal over frontal predominance, calculated as a parietal over frontal predominance index (PFPI). Participants also performed the Digit Span and alpha span tests, which were used to compute an independent index of WMC. Results revealed the classic parietal over frontal P300 predominance. They also indicated that the PFPI decreased as task load increased, owing mainly to an increase in frontal P300 amplitude. Interestingly, WMC was positively correlated with the PFPI, suggesting that individuals with greater WMC exhibited greater parietal over frontal predominance. These correlations did not vary across set sizes. Parietal over frontal predominance was reduced in individuals with lower WMC, who relied more on frontal neural resources. This frontal upregulation may have reflected the recruitment of supplementary attentional executive operations to compensate for less efficient working memory maintenance operations.

The influence of Facebook intrusion and task context on cognitive control

Social networking sites, especially Facebook, have become increasingly popular over the past decades. However, besides the benefits of using Facebook, negative effects in the form of Facebook intrusion are also increasingly pointed out. Much of the research focuses on personality, emotional and social factors related to Facebook intrusion. However, there has been limited research on the relationship between this type of behavioural addiction and cognitive functioning. Consequently, the current study aimed to verify the relationship between Facebook intrusion and cognitive control in light of the dual mechanism of cognitive control model. Additionally, the study aim was to verify the impact of the Facebook-related context on cognitive control (proactive and reactive modes) compared to neutral and positive contexts. The participants (N = 82 young adults, 57 female, M = 22.24 years, SD = 2.67 years, age range 18-35 years) were divided into two groups based on their level of Facebook intrusion. The Facebook intrusion scale was used to assess the level of Facebook intrusion. The AX-CPT task was used to assess proactive and reactive control modes in three task contexts: Facebook-related, neutral and positive. The current study results show that the participants with high Facebook intrusion had greater reactive control than participants with low Facebook intrusion. The differences between Facebook-related, neutral context and positive context were not found. However, the present findings demonstrate the interaction between Facebook intrusion and task context in cognitive control. More specifically, participants with low Facebook intrusion had greater proactive control than participants with high Facebook intrusion in the Facebook-related and positive context.

Involvement of executive control in neural capacity related to working memory in aging: an ERP P300 study

Executive control could be involved in neural capacity, which corresponds to the modulation of neural activity with increased task difficulty. Thus, by exploring the P300-an electrophysiological correlate of working memory-we examined the role played by executive control in both the age-related decline in working memory and neural capacity in aging. Event-related potentials (ERPs) were recorded while younger and older participants performed a Sternberg task with two set sizes (2 vs. 6 items), allowing us to calculate a neural capacity index. Participants also completed two control tasks (Stroop and 3-back tests), which were used to calculate a composite executive control index. Results indicated that working memory performance decreased with aging and difficulty. At the neural level, results indicated that the P300 amplitude varied with aging and also with task difficulty. In the low difficulty condition, frontal P300 amplitude was higher for older than for younger adults, whereas in the high difficulty condition, the amplitude of frontal and parietal P300 did not differ between both age groups. Results also suggest that task difficulty led to a decrease in parietal amplitude in both age groups and to an increase in frontal amplitude in younger but not older adults. Both executive control and frontal neural capacity mediated the age-related variance in working memory for older adults. Moreover, executive control mediated the age-related variance in the frontal neural capacity of older adults. Thus, the present study suggests a model for older adults in which executive control deficits with advancing age lead to less efficient frontal recruitment to cope with task difficulty (neural capacity), which in turn has a negative impact on working memory functioning.

Training and Transfer of Cue Updating in Older Adults Is Limited: Evidence From Behavioral and Neuronal Data

Cognitive control processes, such as updating task-relevant information while switching between multiple tasks, are substantially impaired in older adults. However, it has also been shown that these cognitive control processes can be improved by training interventions, e.g., by training in task switching. Here, we applied an event-related potential (ERP) approach to identify whether a cognitive training improves task-preparatory processes such as updating of relevant task goals. To do so, we applied a pretest-training-posttest design with eight training sessions. Two groups of older adults were either trained in task switching (treatment group) or in performing single tasks (control group) and we compared their performance to a group of untrained younger adults. To foster cue updating in the treatment group, we applied a cue-based switching task in which the two task cues were randomly selected prior to target presentation so that participants had time to prepare for the upcoming task. In contrast, the control group also received task cues but those were redundant as only one task had to be performed. We also examined whether training in cue updating during task switching can be transferred to a similar cognitive control task measuring updating of context information, namely a modified version of the AX-Continuous Performance Task (AX-CPT). The results revealed training-specific improvements in task switching, that is, a larger improvement in blocks requiring switching in comparison to single tasks at the behavioral level. In addition, training specific-effects were also found at the neuronal level. Older adults trained in cue updating while switching showed a reduction in mixing costs in the cue-related P3, indicating an improvement in preparatory updating processes. Additionally, P3 topography changed with training from a very broad to a parietally focused scalp distribution similar to the one found in younger adults. However, we did not obtain training-specific improvements in context updating in the AX-CPT neither at the behavioral level nor at the neuronal level. Results are discussed in the context of the ongoing debate on whether transfer of cognitive training improvements is possible.

Probing the relationship between late endogenous ERP components with fluid intelligence in healthy older adults

The world population is rapidly aging, bringing together the necessity to better understand the advancing age. This characterization may be used to aid early diagnosis and to guide individually-tailored interventions. While some event-related potential (ERP) components, such as the P300 and late positive complex (LPC), have been associated with fluid intelligence (Gf) in young population; little is known whether these associations hold for older people. Therefore, the main goal of this study was to assess whether these ERP components are associated with Gf in the elderly. Fifty-seven older adults performed a continuous performance task (CPT) and a visual oddball paradigm while EEG was recorded. Participants were divided into two groups, according to their performance in the Raven’s Advanced Progressive Matrices test: high-performance (HP) and low-performance (LP). Results showed that the HP group, compared to the LP group, had higher LPC amplitudes in the CPT and shorter P300 latencies in the oddball task, highlighting the role of ERP components as a potential electrophysiological proxy of Gf abilities in the elderly.

Plasticity in brain activity dynamics after task-shifting training in older adults

Cognitive control is supported by a dynamic interplay of transient (i.e., trial-related) brain activation across fronto-parietal networks and sustained (i.e., block-related) activation across fronto-striatal networks. Older adults show disturbances in this dynamic functional recruitment. There is evidence suggesting that cognitive-control training may enable older adults to redistribute their brain activation across cortical and subcortical networks, which in turn can limit behavioral impairments. However, previous studies have only focused on spatial rather than on temporal aspects of changes in brain activation. In the present study, we examined training-related functional plasticity in old age by applying a hybrid fMRI design that sensitively tracks the spatio-temporal interactions underlying brain-activation changes. Fifty healthy seniors were assigned to a task-shifting training or an active-control group and their pretest/posttest activation-change maps were compared against 25 untrained younger adults. After training, older adults showed the same performance as untrained young adults. Compared to the control group, task-shifting training promoted proactive (i.e., early, cue-related) changes in transient mechanisms supporting the maintenance and top-down biasing of task-set representations in a specific prefrontal circuitry; reactive (i.e., late, probe-related) changes in transient mechanisms supporting response-selection processes in dissociable fronto-parietal networks; overall reductions of sustained activation in striatal circuits. Results highlight the importance of spatio-temporal interactions in training-induced neural changes in age.

Does the Effort of Processing Potential Incentives Influence the Adaption of Context Updating in Older Adults?

A number of aging studies suggest that older adults process positive and negative information differently. For instance, the socioemotional selectivity theory postulates that older adults preferably process positive information in service of emotional well-being (Reed and Carstensen, 2012). Moreover, recent research has started to investigate whether incentives like gains or losses can influence cognitive control in an ongoing task. In an earlier study (Schmitt et al., 2015), we examined whether incentive cues, indicating potential monetary gains, losses, or neutral outcomes for good performance in the following trial, would influence older adults’ ability to exert cognitive control. Cognitive control was measured in an AX-Continuous-Performance-Task (AX-CPT) in which participants had to select their responses to probe stimuli depending on a preceding context cue. In this study, we did not find support for a positivity effect in older adults, but both gains and losses led to enhanced context processing. As the trial-wise presentation mode may be too demanding on cognitive resources for such a bias to occur, the main goal of the present study was to examine whether motivational mindsets, induced by block-wise presentation of incentives, would result in a positivity effect. For this reason, we examined 17 older participants (65–76 years) in the AX-CPT using a block-wise presentation of incentive cues and compared them to 18 older adults (69–78 years) with the trial-wise presentation mode from our earlier study (Schmitt et al., 2015). Event-related potentials were recorded to the onset of the motivational cue and during the AX-CPT. Our results show that (a) older adults initially process cues signaling potential losses more strongly, but later during the AX-CPT invest more cognitive resources in preparatory processes like context updating in conditions with potential gains, and (b) block-wise and trial-wise presentation of incentive cues differentially influenced cognitive control. When incentives were presented block-wise, the above described valence effects were consistently found. In contrast, when incentives were presented trial-wise, the effects were mixed and salience as well as valence effects can be obtained. Hence, how positive and negative incentive cues influence cognitive control in older adults is dependent on demands of cue processing.

The P3 Parietal-To-Frontal Shift Relates to Age-Related Slowing in a Selective Attention Task

Abstract. Older adults recruit relatively more frontal as compared to parietal resources in a variety of cognitive and perceptual tasks. It is not yet clear whether this parietal-to-frontal shift is a compensatory mechanism, or simply reflects a reduction in processing efficiency. In this study we aimed to investigate how the parietal-to-frontal shift with aging relates to selective attention. Fourteen young and 26 older healthy adults performed a color Flanker task under three conditions (incongruent, congruent, neutral) and event-related potentials (ERPs) were measured. The P3 was analyzed for the electrode positions Pz, Cz, and Fz as an indicator of the parietal-to-frontal shift. Further, behavioral performance and other ERP components (P1 and N1 at electrodes O1 and O2; N2 at electrodes Fz and Cz) were investigated. First young and older adults were compared. Older adults had longer response times, reduced accuracy, longer P3 latencies, and a more frontal distribution of P3 than young adults. These results confirm the parietal-to-frontal shift in the P3 with age for the selective attention task. Second, based on the differences between frontal and parietal P3 activity the group of older adults was subdivided into those showing a rather equal distribution of the P3 and older participants showing a strong frontal focus of the P3. Older adults with a more frontally distributed P3 had longer response times than participants with a more equally distributed P3. These results suggest that the frontally distributed P3 observed in older adults has no compensatory function in selective attention but rather indicates less efficient processing and slowing with age.