Daniela Czernochowski

Age-related differences in familiarity and recollection: ERP evidence from a recognition memory study in children and young adults

Using event-related potentials (ERPs), we examined the relative contributions of familiarity and recollection to recognition memory for items and their study contexts in school-aged children and adults. Whereas adults were able to selectively accept target items and to reject familiar nontarget items in an exclusion task, this discrimination was more difficult for children, as was evident in the high false alarm rates to nontargets even when item memory was controlled for. The analysis of the adults’ ERPs revealed more flexible and task-appropriate retrieval mechanisms, as was evident in the correlates of familiarity, recollection, and nontarget retrieval, as well as in postretrieval evaluation. In contrast, children’s ERPs revealed a parietal old/new effect for targets taken as a putative correlate of recollection. These findings suggest that children rely predominantly on recollection during recognition judgments, even in the absence of efficient memory control processes. The latter processes enable adults to monitor and verify the retrieved information and to control nontarget retrieval in the service of adequate source memory performance.

Use it or lose it? SES mitigates age-related decline in a recency/recognition task

An important goal of aging research is to determine factors leading to individual differences that might compensate for some of the deleterious effects of aging on cognition. To determine whether socio-economic status (SES) plays a role in mitigating age-related decrements in the recollection of contextual details, we categorized older participants into low- and high-SES groups. Event-related potentials (ERPs) and behavioral data were recorded in a picture memory task involving recency and recognition judgments. Young, old-low and old-high SES groups did not differ in recognition performance. However, on recency judgments, old-low subjects performed at chance, whereas old-high subjects did not differ significantly from young adults. Consistent with their preserved recency performance, a long-duration frontal negativity was significantly larger for recency compared to recognition trials in the ERPs of the old-high SES group only. These data suggest that older adults with higher SES levels can use strategies to compensate for the adverse effects of aging in complex source memory tasks by recruiting additional neural resources apparently not required by the young.

On why not to rush older adults--relying on reactive cognitive control can effectively reduce errors at the expense of slowed responses.

According to the dual-mechanisms of cognitive control framework (DMC), older adults rely predominantly on reactive as opposed to proactive control. As a result, we expected elevated response conflict for older relative to younger adults with increasing task difficulty. Response-locked ERP activity was examined separately for fast and slow responses (representing proactive and reactive control, respectively) at low, medium, and high levels of difficulty. Older adults recruited reactive control more often than the young, as reflected by increased behavioral costs and enhanced pre-response negativity (PRN). No age differences in conflict detection (medial frontal negativity, MFN) were evident at low levels of difficulty, but response conflict increased along with difficulty for older adults. These data provide empirical support for the DMC suggesting that aging is associated with a less efficient reactive-control mode of processing.

Cross-frequency phase coupling of brain rhythms during the orienting response

A critical function of the brains orienting response is to evaluate novel environmental events in order to prepare for potential behavioral action. Here, measures of synchronization (power, coherence) and nonlinear cross-frequency phase coupling (m:n phase locking measured with bicoherence and cross-bicoherence) were computed on 62-channel electroencephalographic (EEG) data during a paradigm in which unexpected, highly-deviant, novel sounds were randomly intermixed with frequent standard and infrequent target tones. Low frequency resolution analyses showed no significant changes in phase coupling for any stimulus type, though significant changes in power and synchrony did occur. High frequency resolution analyses, on the other hand, showed significant differences in phase coupling, but only for novel sounds compared to standard tones. Novel sounds elicited increased power and coherence in the delta band together with m:n phase locking (bicoherence) of delta:theta (1:3) and delta:alpha (1:4) rhythms in widespread fronto-central, right parietal, temporal, and occipital regions. Cross-bicoherence revealed that globally synchronized delta oscillations were phase coupled to theta oscillations in central regions and to alpha oscillations in right parietal and posterior regions. These results suggest that globally synchronized low frequency oscillations with phase coupling to more localized higher frequency oscillations provide a neural mechanism for the orienting response.

Does frequency matter? ERP and behavioral correlates of monitoring for rare and frequent prospective memory targets

Behavioral and event-related potential (ERP) correlates of monitoring in an event-based prospective memory (PM) task were compared during blocks with rare versus frequent PM target presentations relative to an ongoing-task only condition. For both rare and frequent PM conditions, behavioral interference costs in terms of longer reaction times (RTs) were observed. Likewise, during both PM blocks a sustained ERP positivity with a frontal focus was identified on ongoing-task trials. While PM target identification and RT interference costs were larger during the PM-frequent relative to the PM-rare condition, the same sustained frontal positivity was observed during both PM blocks. These findings suggest that successful monitoring is associated with the adoption of a more general prospective retrieval mode, irrespective of target frequency. Moreover, preparatory attentional modulations directed at relevant target features played an important role for subsequent PM performance, as evident in larger P2 amplitudes during PM blocks.

The development of anticipatory cognitive control processes in task-switching: An ERP study in children, adolescents, and young adults

To investigate the development of advance task-set updating and reconfiguration, behavioral and event-related potential (ERP) data were recorded in children (9-10 years), adolescents (13-14 years), and young adults (20-27 years) in a cued task-switching paradigm. In pure blocks, the same task was repeated. In mixed blocks, comprised of stay and switch trials, two tasks were intermixed. Age differences were found for stay-pure performance (mixing costs) in the 600-ms but not in the 1200-ms cue-target interval (CTI). Children showed larger reaction time mixing costs than adults. The ERPs suggested that the larger costs were due to delayed anticipatory task-set updating in children. Switch-stay performance decrements (switch costs) were age-invariant in both CTIs. However, ERP data suggested that children reconfigured the task-set on some stay trials, rather than only on switch trials, suggesting the continued maturation of task-set reconfiguration processes.

ERPs dissociate proactive and reactive control: Evidence from a task-switching paradigm with informative and uninformative cues

According to the dual mechanism of control (DMC) framework, cognitive control can be recruited proactively to prevent response conflict when advance preparation is feasible or is up-regulated to overcome response conflict after it is detected. This study aimed at empirically dissociating proactive and reactive control processes proposed by the DMC and identifying corresponding event-related potential (ERP) correlates. Behavioral and electrophysiological indices of cognitive control were measured during a task-switch paradigm with or without informative advance cues, in which proactive control was feasible or not. Proactive control was associated with a (right-) frontal sustained ERP modulation during the cue–target interval. In line with the successful recruitment of proactive control, informative, as compared with uninformative, cue conditions were associated with reduced behavioral and ERP correlates of conflict. ERP correlates of conflict were evident both during conflict detection upon target presentation (Ninc) and during conflict resolution—in particular, following uninformative cues. Reactive control assumed to support conflict resolution was associated with a (left-) frontal transient preresponse ERP modulation for uninformative, but not informative, cue conditions. Together, these data suggest that complementary proactive and reactive control processes operate in concert to flexibly support goal-directed behavior in response to variable task-demands, by either preventing or resolving response conflicts, as they are detected or anticipated.

ERP Evidence for Scarce Rule Representation in Older Adults Following Short, but Not Long Preparatory Intervals.

The focus of the present study was to examine the cognitive processes comprising advance preparation – rule representation, task-set updating, and task-set reconfiguration – in young (20–25 years) and older adults (61–83 years). Specifically, this study aimed at further characterizing age-related differences in advance preparation, and evaluating how additional time to prepare might reduce behavioral costs in older adults. In line with previous findings, reaction time mixing costs were slightly larger for older compared to young adults, whereas behavioral switch costs were age-invariant. Following short preparation (600 ms), smaller antero-frontal event-related potential (ERP) correlates of rule representation were associated with pronounced congruency costs in older adults. Centro-parietal ERP correlates of task-set updating and task-set reconfiguration were not delayed, but smaller in magnitude for older compared to young adults. Longer preparation (1200 ms) enabled older adults to re-activate relevant task rules, as evident in reduced congruency costs, and temporally sustained ERP correlates of task-set updating and rule representation well beyond 600 ms. Age-invariant switch costs appear related to additional, potentially compensatory frontal activity recruited by older adults to overcome difficulties in task-set reconfiguration.

Does this sound familiar? Effects of timbre change on episodic retrieval of novel melodies

Three experiments investigated episodic retrieval of novel melodies and tested how a change in timbre between study and test affects the two processes underlying recognition memory, conscious recollection and familiarity. In Experiments 1 and 2, conscious recollection and familiarity were operationalized using the remember/know paradigm. We additionally assessed the influence of the number of presentations during learning in Experiment 1, and the effect of massed versus distributed learning in Experiment 2. Experiment 3 confirmed that participants could also indicate a change in timbre explicitly (same versus different timbre classifications). In all experiments, melodies were better recognized when the timbre at study and test was identical. Effects of timbre change were more pronounced for recollection than familiarity. Distributed learning specifically enhanced the same-timbre advantage on recollection. Together, these results suggest that timbre serves both as a context cue and as an integrated feature of a melody.

Sometimes we have to intentionally focus on the details: Incidental encoding and perceptual change decrease recognition memory performance and the ERP correlate of recollection

Prior studies suggest that memory retrieval is based on two independent processes: Recollection and familiarity. Here, we investigated the role of incidental and intentional encoding, and specifically whether perceptual changes between study and test affects behavioral and electrophysiological correlates of both retrieval processes. During retrieval, participants distinguished between identical and changed exemplars as well as novel distractors. Following incidental encoding, participants had difficulty identifying changed exemplars; item and feature recognition increased after intentional encoding, in particular for changed exemplars. Reflecting this increase in memory performance, the ERP correlate of recollection was larger after intentional encoding and for identical item repetitions, whereas the ERP correlate for familiarity was largely unaffected. Pre-response old/new effects corresponding to later aspects of recollection (700-1000 ms relative to stimulus onset) were larger in response-compared to stimulus-locked averages, but also of similar magnitude for identical and changed exemplars. These results corroborate previous findings suggesting that the electrophysiological signature of recollection is modulated as a function of memory performance. The role of task characteristics and material retrieved from memory for modulations in familiarity-based retrieval processes is discussed.