Age-related differences in novelty and target processing among cognitively high performing adults

Previous research on age-related changes in ERP components in response to novel and target stimuli has not carefully controlled for differences in level of cognitive status between age groups, which may have contributed to the common findings of increased P3 latency, decreased P3 amplitude, and altered P3 scalp distribution. Here, cognitively high-performing (top third based on published norms) old, middle-aged, and young adults matched for IQ, education, and gender participated in a novelty oddball paradigm. There were no age-associated differences in P3 latency. Older adults had a larger, more anteriorly distributed P3 amplitude to all stimulus types, even repetitive standards, suggesting they may rely on increased resources and effortful frontal activity to successfully process any kind of visual stimulus. However, after controlling for this non-specific age-related processing difference, the amplitude and scalp distribution of the P3 component to novel and target stimuli were comparable across age groups, indicating that for cognitively high functioning elders there may be no age-related differences specific to the processing of novel and target events as indexed by the P3 component.     

Cognitive status impacts age-related changes in attention to novel and target events in normal adults

In this study, the authors investigated the relationship between the cognitive status of normal adults and age-related changes in attention to novel and target events. Old, middle-age, and young subjects, divided into cognitively high and cognitively average performing groups, viewed repetitive standard stimuli, infrequent target stimuli, and unique novel visual stimuli. Subjects controlled viewing duration by a button press that led to the onset of the next stimulus. They also responded to targets by pressing a foot pedal. The amount of time spent looking at different kinds of stimuli served as a measure of visual attention and exploratory activity. Cognitively high performers spent more time viewing novel stimuli than cognitively average performers. The magnitude of the difference between cognitively high and cognitively average performing groups was largest among old subjects. Cognitively average performers had slower and less accurate responses to targets than cognitively high performers. The results provide strong evidence that the link between engagement by novelty and higher cognitive performance increases with age. Moreover, the results support the notion of there being different patterns of normal cognitive aging and the need to identify the factors that influence them.     

P3a from visual stimuli: typicality,task, and topography

A visual three-stimulus (target, nontarget, standard) paradigm was employed in which subjects responded only to the target. Nontarget stimulus properties were varied systematically to evaluate how stimulus typicality (non-novel vs. novel) across task discrimination (easy vs. difficult) conditions affects P3a scalp topography. Nontarget stimuli consisted of letters, small squares, large squares, and novel patterns; discrimination difficulty between the target and standard was varied across conditions. When the discrimination was easy, P300 amplitude was larger for the target than the nontarget with parietal maximums for both. In contrast, when the discrimination was difficult, nontarget amplitude (P3a) was larger and earlier than the target P300 over the frontal/central electrode sites, whereas target amplitude (P3b) was larger parietally and occurred later. P3a was largest when elicited by either the large square or novel pattern stimuli. The findings suggest that stimulus context as defined by the target/standard discrimination difficulty rather than stimulus novelty determines P3a generation.     

An ERP developmental study of repetition priming by auditory novel stimuli

Event-related potentials were recorded from participants 5–7, 9–11, 14–16, and 22–28 years old during an auditory novelty oddball task. In this task, stimuli about which the participant is not instructed (i.e., novel or uncategorized) typically elicit a more frontally oriented P3 scalp topography (novelty P3). In contrast, stimuli to which the participant must respond (i.e., target or precategorized) elicit a P3 with a more posterior scalp topography. Repetition of identical novel stimuli led to a similar reduction in novelty P3 amplitude for all age groups. Moreover, with repetition the shift in scalp topography of the novelty P3 to a more parietally oriented distribution was similar in children and adults. A second component, the P3₂ (assumed to be an analog of the P3b), exhibited a repetition priming effect in both the adults and the youngest children. The fact that age-related differences induced by novel repetition were small and not systematic indicates that the processing of novel information is similar across a wide age range.     

Age and novelty: event-related potentials to visual stimuli within an auditory oddball--visual detection task.

Age-related change of event-related potentials to novel visual stimuli was investigated while participants attended to both auditory and visual stimulation. Meaningful but irrelevant pictures (novel stimuli) were presented to younger (mean=21.8, range=18-26 years) and older (mean=70.0, range=60-78) participants (10 in each group). The participants were performing an auditory oddball task and counting silently the changes of a visually presented letter. In the younger group novel stimuli elicited a posterior positivity in the 220-255 ms range. This component habituated to the repetition of the same picture. In the older group this component had longer latency, and did not habituate. A later positivity had shorter latency and larger amplitude in the younger group, but this positivity was preceded by a negative component (N2b) only in the elderly. Results show decreased sensitivity to the content of the visual stimuli in an earlier stage of novelty processing in the elderly, and the age-related slowing of both orientation-related and task-related processes.     

Behavioural and electrophysiological effects of visual paired associate context manipulations during encoding and recognition in younger adults,older adults and older cognitively declined adults

The current study examined the EEG of young, old and old declined adults performing a visual paired associate task. In order to examine the effects of encoding context and stimulus repetition, target pairs were presented on either detailed or white backgrounds and were repeatedly presented during both early and late phases of encoding. Results indicated an increase in P300 amplitude in the right parietal cortex from early to late stages of encoding in older declined adults, whereas both younger adults and older controls showed a reduction in P300 amplitude in this same area from early to late phase encoding. In the right hemisphere, stimuli encoded with a white background had larger P300 amplitudes than stimuli presented with a detailed background; however, in the left hemisphere, in the later stages of encoding, stimuli presented with a detailed background had larger amplitudes than stimuli presented with a white background. Behaviourally, there was better memory for congruent stimuli reinstated with a detailed background, but this finding was for older controls only. During recognition, there was a general trend for congruent stimuli to elicit a larger amplitude response than incongruent stimuli, suggesting a distinct effect of context reinstatement on underlying patterns of physiological responding. However, behavioural data suggest that older declined adults showed no memory benefits associated with context reinstatement. When compared with older declined adults, younger adults had larger P100 amplitude responses to stimuli presented during recognition, and overall, younger adults had faster recognition reaction times than older control and older declined adults. Further analysis of repetition effects and context-based hemispheric asymmetry may prove informative in identifying declining memory performance in the elderly, potentially before it becomes manifested behaviourally.     

A Further Analysis of Age and Sleep Deprivation Effects

Subjective, persistence/attention, precision, and cognitively demanding measures were obtained across two nights' sleep deprivation to compare the performance of 50–59 and 18–22 yr old men. The younger subjects had the larger subjective decrements while the older subjects had the larger decrements on the persistence tasks. The results were mixed on the precision and cognitively demanding tasks.     

Introversion, attention and the late positive component of event-related potentials

Variation in P3 amplitude across normal individuals under the same experimental conditions has been routinely observed. The possibility that such variation reflects individual differences in the allocation of attention was examined by comparing P3 amplitude in introverts and extraverts, who are thought to differ in the allocation of attention during monotonous tasks.

Event-related potentials were recorded while the subjects participated in a lengthy stimulus prediction task. P3 amplitude was determined by principal components analysis and it was found to be significantly larger for the introverts than for the extraverts. This finding is interpreted as evidence that P3 amplitude is sensitive to individual differences in the allocation of attention.     

P3a from white noise

P3a and P3b event-related brain potentials (ERPs) were elicited with an auditory three-stimulus (target, distracter, and standard) discrimination task in which subjects responded only to the target. Distracter stimuli consisted of white noise or novel sounds with stimulus characteristics perceptually matched. Target/standard discrimination difficulty was manipulated by varying target/standard pitch differences to produce relatively easy, medium, and hard tasks. Error rate and response time increased with increases in task difficulty. P3a was larger for the white noise compared to novel sounds, maximum over the central/parietal recording sites, and did not differ in size across difficulty levels. P3b was unaffected by distracter type, decreased as task difficulty increased, and maximum over the parietal recording sites. The findings indicate that P3a from white noise is robust and should be useful for applied studies as it removes stimulus novelty variability. Theoretical perspectives are discussed.     

Stimulus probability and motor response in young and old adults: an ERP study

The effects of responding hand and stimulus probability were investigated in young and old subjects in an RT task in which both rare and frequent stimuli required a response. It was found that the effect of stimulus probability was less pronounced in old subjects than in young, and that the latency of P3 was longer in the elderly, although their RTs were not different from young subjects. ERPs for right hand responses were larger than for left hand responses; this difference was discernible already in the P2 and N2 peaks of the ERP. A tentative explanation is offered for these large and unexpected hand differences. An interpretation in terms of an age-related decrease in resources is proposed for the increased P3 latency and the decreased probability effect on P3 amplitude in old subjects.     

Investigating the age‐related “anterior shift” in the scalp distribution of the P3b component using principal component analysis

An age‐related “anterior shift” in the distribution of the P3b is often reported. Temporospatial principal component analysis (PCA) was used to investigate the basis of this observation. ERPs were measured in young and old adults during a visual oddball task. PCA revealed two spatially distinct factors in both age groups, identified as the posterior P3b and anterior P3a. Young subjects generated a smaller P3a than P3b, while old subjects generated a P3a that did not differ in amplitude from their P3b. Rather than having a more anteriorly distributed P3b, old subjects produced a large, temporally overlapping P3a. The pattern of the age‐related “anterior shift” in the P3 was similar for target and standard stimuli. The increase in the P3a in elderly adults may not represent a failure to habituate the novelty response, but may reflect greater reliance on executive control operations (P3a) to carry out the categorization/updating process (P3b).     

The effect of intention to learn novel, environmental sounds on the novelty P3 and old/new recognition memory.

Brain electrical activity was recorded while 32 young adults listened to frequent tones, infrequent target tones, and infrequent novel environmental sounds (some of which repeated). Subjects in the incidental group were not informed about the novel sounds, while subjects in the intentional group were informed and, in addition, were asked to memorize them for a subsequent memory test. Following the novelty oddball task, all subjects were given an old/new sound recognition memory task. The novelty P3 showed a more anterior scalp distribution and an effect of repetition in the incidental compared to the intentional group, suggesting that pre-categorizing the novel sounds influenced how they were processed. For the intentional group only, a subsequent memory effect was elicited by novel sounds that were subsequently recognized compared to those that were not, although both groups showed robust old/new ERP effects during the recognition task. The robust subsequent memory effects in the intentional group were associated with greater recognition accuracy of familiar environmental sounds relative to the incidental group. These data suggest that the encoding activity reflected in the ERP subsequent memory effect may have engendered an advantage in subsequent recognition memory performance.     

Age-dependent changes of auditory evoked potentials--effect of task difficulty

The goal of this study was to evaluate the patterns of age-dependent changes of P3 components of auditory event-related potentials exploring the effects of task difficulty. The participants (age span: 19-68 years, n=55, divided into five age groups) took part in an easy and in a difficult two-tone oddball frequency discrimination task with speed or accuracy instructions, and in a novelty oddball task. The latency of the P3 components increased with aging. While in the easy task a linear P3b latency increase could be seen, in the difficult tasks (difficult frequency discrimination or distracting novel stimuli) an accelerated latency increase was observed for the P3b and P3a. In the two-tone oddball paradigm age had no effect on P3b amplitude, but in the novelty oddball task the amplitude of P3 potentials decreased with age. These results indicate that distracting stimuli increase task demands, and in difficult tasks decay can be observed more easily due to the accumulation of various processing mechanisms characterizing aging.     

Event-related potentials in the dual task paradigm: P300 discriminates engaging and non-engaging films when film-viewing is the primary task.

Five groups of subjects (11-16/group) were run in three experiments. In each study P300 amplitude and latency were studied as a function of three sensory task conditions: (1) baseline (oddball task: target and non-target tones only); (2) boring film viewing plus oddball task; and (3) exciting film viewing plus oddball task. In Experiment I, target probability was P = 0.22. In Experiments II and III, each of two groups of subjects was run at P = 0.22 or P = 0.33. Two different exciting films and two different boring films were used. Oddball-target amplitude was found to consistently decrease from baseline to boring to exciting film-viewing conditions at P = 0.22. At P = 0.33, the 2-film discrimination was successful in one of two experiments. P300 amplitude consistently differed from baseline to film-viewing conditions. For the non-target (frequent) tones, the smaller P300 amplitudes consistently discriminated boring and exciting films, as well as single from dual tasks. For target P300 latency, single (baseline) and dual (film-watching) conditions were always discriminable, but boring and exciting films were not discriminable. There were no effects on non-target P300 latency. N100 amplitude discriminated baseline and film viewing conditions, but not boring and engaging films.     

Processing of expected and unexpected monetary performance outcomes in healthy older subjects

The feedback-related negativity (FRN), an event-related potential (ERP) component reflecting feedback processing in the anterior cingulate cortex (ACC), has consistently been found to be reduced in healthy aging, whereas behavioral findings regarding age-related changes in decision making and feedback-based learning are inconsistent. This study aimed to elucidate similarities and differences between healthy younger and older subjects in the processing of monetary performance feedback focusing on effects of reward expectancy. Eighteen younger and 20 older subjects completed a feedback learning task, in which a rule could be learned to predict the reward probabilities associated with particular stimuli. Older subjects showed evidence of slower learning than younger subjects. In both younger and older subjects, the amplitude difference between nonreward and reward in the FRN time window was larger for unexpected than expected outcomes, driven by modulations of negative feedback ERPs. Consistent with previous findings, the amplitude difference tended to be generally reduced in older subjects. P300 amplitude was larger for reward than nonreward in both groups, and interactions between valence and probability indicated that only the P300 for reward was modulated by expectancy. Despite general changes of outcome-related ERPs in healthy aging, older subjects show evidence of preserved effects of expectancy on the processing of monetary feedback.     

Event-related potentials index cognitive style differences during a serial-order recall task.

Working memory and attentional inhibition processes (jointly symbolized here as WM/I) have been proposed to explain cognitive style differences in Field Dependence-Independence (FDI). FI relative to FD subjects have been found to use more effectively WM/I to operate on task-relevant information. The purpose of this study was to determine whether cognitive style differences are revealed as differences in ERP activity in a novel WM/I task. A serial-order recall task served to manipulate memory load by varying the amount and kind of information to be elaborated and retained in WM in order of temporal appearance (S1, S2); recall demand of the serial-order judgment (S3) was also concurrently varied. FI subjects engaged in deeper WM processing during the high memory load conditions relative to FD subjects; and this was measured as a higher amplitude slow negative wave (SNW), over the centro-parietal scalp extending to the frontal scalp, during the retention interval. In contrast, P300 amplitude was larger for FD subjects in the high memory load conditions following S1, which corresponded with a reduced amplitude SNW. We suggest that inhibitory processes indexed by P300, which FD subjects must mobilize to change their usually global-perceptual (i.e. shallow) attentional strategy for processing task information, may have resulted in less mental-attentional (WM/I) resources available to them during the task's retention phase (Rosen and Engle, 1997). Thus, ERP methods can be used to investigate differences in cognitive style.     

The relationship of age and cardiovascular fitness to cognitive and motor processes

Older and younger aerobically trained and sedentary adults participated in an S1-S2-S3 paradigm designed to elicit event-related potential (ERP) and behavioral responses to determine the influence of cardiovascular fitness on cognitive and motor processes. The paradigm provided warning (S1) as to the difficulty level of an upcoming decision task (S2). Participants had to decide the taller of two bars on presentation of S2 but hold their response until S3, to which they indicated their choice motorically. Results revealed age-related differences for ERP measures as older participants showed increased amplitude of the stimulus preceding negativity (SPN) prior to S2, and longer latencies and equipotentiality of P3 in response to S2. Fitness effects were also observed for the contingent negative variation (CNV) with decreased amplitude for fit relative to sedentary individuals. Age interacted with fitness for P3 latency to S2 as older sedentary individuals showed the longest latency followed by older fit and both younger groups. No significant group differences were observed for reaction time (RT) to S3. Therefore, physical fitness is associated with attenuation of cognitive decline in older individuals and greater economy of motor preparation for both young and older participants.     

An electrophysiological index of stimulus unfamiliarity

This study investigated the functional significance of the N2 response to novel stimuli. In one condition, background, target, and deviant stimuli were simple geometric figures. In a second condition, all stimulus types were unfamiliar/unusual figures. In a third condition, background and target stimuli were unusual figures and deviant stimuli were simple shapes. Unusual figures, whether they were deviant, target, or background stimuli, evoked larger N2 responses than their simple, familiar counterparts. N2 elicited by an unusual background stimulus was larger than that evoked by simple, deviant stimuli, a pattern opposite that exhibited by the subsequent P3. Deviance from immediate context had limited influence over N2 amplitude. The results suggest that novelty N2 and novelty P3 reflect the processing of different aspects of "novel" visual stimuli. The novelty P3 is particularly sensitive to deviation from immediate context. In contrast, the novelty N2 is sensitive to deviation from long-term context that renders a stimulus unfamiliar and difficult to encode.     

Age effects on heart rate,sustained potential,and P3 responses during reaction-time tasks

—Relationships between physiological responses and slowed reaction time (RT) among elderly subjects were tested in 48 healthy young, middle-aged, and elderly men (mean ages 24, 45, and 71 years) using signaled simple and choice RT tasks. There were age reductions in P3 amplitude and heart rate (HR) deceleration, but no effects of age on P3 latency. Sustained potential (SP or CNV) amplitude paradoxically increased with age, possibly indicating weaker inhibitory function. P3 amplitude, SP amplitude, and HR deceleration were most strongly correlated with RT among younger subjects, but SP amplitude was correlated with RT in the elderly group during the choice task. HR deceleration shared a small amount of variance with SP amplitude and RT in the young group. There was no HR-SP-RT relationship in the older groups. Choice-simple task differences in P3 amplitude and RT were correlated in the young and elderly groups. The results suggest that HR, SP, and P3 responses may reflect physiological processes related to the slower RTs of healthy elderly subjects.     

Early and Late Selection in Young and Old Adults: An Event-Related Potential Study

The present experiment investigated differences in processing between young and old adults in a combined visual selection-memory search paradigm. No evidence was found for age-related differences in early visual selective attention. The elderly achieved relatively fast reaction times in the memory search task at the cost of a high error percentage. From these findings, and from the morphology of the event-related potential, it was concluded that old subjects perform controlled memory search more superficially than young subjects, In both old and young subjects high memory load was associated with decreased positivity in the P3 and Slow Wave area. This is interpreted in terms of Okita et al.'s(1985) concept of search negativity. N2 amplitude was found to be larger to non-target trials for both attended and unattended inputs. The latter result is discussed in relation to theories about N2 as an indicator of automatic mismatch detection.