Flanker interference in young and older participants as reflected in event-related potentials

Effects of aging and involuntary capture of attention on event-related potentials associated with the processing of and the response to a target stimulus

The main aim of the present study was to assess whether aging modulates the effects of involuntary capture of attention by novel stimuli on performance, and on event-related potentials (ERPs) associated with target processing (N2b and P3b) and subsequent response processes (stimulus-locked Lateralized Readiness Potential -sLRP- and response-locked Lateralized Readiness Potential -rLRP-). An auditory-visual distraction-attention task was performed by 77 healthy participants, divided into three age groups (Young: 21-29, Middle-aged: 51-64, Old: 65-84 years old). Participants were asked to attend to visual stimuli and to ignore auditory stimuli. Aging was associated with slowed reaction times, target stimulus processing in working memory (WM, longer N2b and P3b latencies) and selection and preparation of the motor response (longer sLRP and earlier rLRP onset latencies). In the novel relative to the standard condition we observed, in the three age groups: (1) a distraction effect, reflected in a slowing of reaction times, of stimuli categorization in WM (longer P3b latency), and of motor response selection (longer sLRP onset latency); (2) a facilitation effect on response preparation (later rLRP onset latency), and (3) an increase in arousal (larger amplitudes of all ERPs evaluated, except for N2b amplitude in the Old group). A distraction effect on the stimulus evaluation processes (longer N2b latency) were also observed, but only in middle-aged and old participants, indicating that the attentional capture slows the stimulus evaluation in WM from early ages (from 50 years onwards, without differences between middle-age and older adults), but not in young adults.

The boundary condition for observing compensatory responses by the elderly in a flanker-task paradigm

This study aimed to establish a baseline condition to observe ERP responses for older adults in a conventional flanker-task paradigm, in which neither a reversal response rule toward a target nor a color-coded target was employed. In addition, this study aimed to examine whether the previous finding of the compensatory responses reflected on event-related potential (ERP) for older adults in performing a flanker task was due to the specific demand of the reversal response rule toward a target or simply due to the pop-out effect with a singleton target manipulation. The results of the current study showed that (1) some of the previously thought-to-be compensatory ERP responses might not really reflect compensatory responses; (2) the previous finding of age-related ERP compensatory responses was mainly due to the manipulation of the reversal response rule condition; and (3) in some scenarios of flanker-task paradigms, older adults were just as capable as younger adults in conquer with the flanker interference even though no ERP compensatory responses were found.

Age-related differences in distractor interference on line bisection

Using a bisection paradigm, we investigated age-related differences in susceptibility to distractor interference. Older and younger participants were asked to bisect a horizontal line flanked by a pair of distractors, placed in either left or right hemispace. The results showed that (1) in both groups the distractors interfered with line bisection so that the localization of subjective midpoint was selectively shifted away from their position; (2) the shifting of subjective midpoint was greater in the older than in the younger group when the distractors were placed in the left hemispace. We suggest that the increase of the bisection bias in the older group depends on changes in attentional mechanisms involved in inhibiting irrelevant information.

Selective Age Effects on Visual Attention and Motor Attention during a Cued Saccade Task

Objective. Visual information is often used to guide purposeful movement. However, older adults have impaired responses to visual information, leading to increased risk for injuries and potential loss of independence. We evaluated distinct visual and motor attention contributions to a cued saccade task to determine the extent to which aging selectively affects these processes. Methods. Nineteen healthy young (18–28 years) and 20 older (60–90 years) participants performed a cued saccade task under two conditions. We challenged motor attention by changing the number of possible saccade targets (1 or 6). Results. Older adults had difficulty in inhibiting unwanted eye movements and had greater eye movement inaccuracy in the hard condition when compared to the younger adults and to the easy condition. Also, an inverse relation existed between performance on the visual and motor components of the task in older adults, unlike younger adults. Conclusions. Older adults demonstrated difficulty in both inhibiting irrelevant saccade targets and selecting correct saccade endpoints during more complex tasks. The shift in relations among attention measures between the younger and older participants may indicate a need to prioritize attentional resources with age. These changes may impact an older adult's ability to function in complex environments.

Ageing differentially affects neural processing of different conflict types-an fMRI study

Interference control and conflict resolution is affected by ageing. There is increasing evidence that ageing does not compromise interference control in general but rather shows distinctive effects on different components of interference control. Different conflict types, [e.g., stimulus-stimulus (S-S) or stimulus-response (S-R) conflicts] trigger different cognitive processes and thus activate different neural networks. In the present functional magnetic resonance imaging (fMRI) study, we used a combined Flanker and Stimulus Response Conflict (SRC) task to investigate the effect of ageing on S-S and S-R conflicts. Behavioral data analysis revealed larger SRC effects in elderly. fMRI Results show that both age groups recruited similar regions [caudate nucleus, cingulate gyrus and middle occipital gyrus (MOG)] during Flanker conflict processing. Furthermore, elderly show an additional activation pattern in parietal and frontal areas. In contrast, no common activation of both age groups was found in response to the SRC. These data suggest that ageing has distinctive effects on S-S and S-R conflicts.

Brain mechanisms underlying the effects of aging on different aspects of selective attention

The ability to suppress irrelevant information declines with age, while the ability to enhance relevant information remains largely intact. We examined mechanisms behind this dissociation in an fMRI study, using a selective attention task in which relevant and irrelevant information appeared simultaneously. Slowing of response times due to distraction by irrelevant targets was larger in older than younger participants. Increased distraction was related to larger increases in activity and connectivity in areas of the dorsal attention network, indicating a more pronounced (re-)orientation of attention. The decreases in accuracy in target compared to nontarget trials were smaller in older compared to younger participants. In older adults we found increased recruitment of areas in the fronto-parietal control network (FPCN) during target detection. Moreover, older adults showed increased connectivity between the FPCN, supporting cognitive control, and somatomotor areas implicated in response selection and execution. This connectivity increase was related to improved target detection, suggesting that older adults engage additional cognitive control, which might enable the observed intact performance in detecting and responding to target stimuli.

Electrophysiological correlates of amnestic mild cognitive impairment in a simon task

Amnestic mild cognitive impairment (aMCI) represents a prodromal stage of Alzheimer`s disease (AD), especially when additional cognitive domains are affected (Petersen et al., 2009). Thus, single-domain amnestic MCI (sdaMCI) and multiple-domain-amnestic MCI (mdaMCI) biomarkers are important for enabling early interventions to help slow down progression of the disease. Recording event-related potentials (ERPs) is a non-invasive and inexpensive measure of brain activity associated with cognitive processes, and it is of interest from a clinical point of view. The ERP technique may also be useful for obtaining early sdaMCI and mdaMCI biomarkers because ERPs are sensitive to impairment in processes that are not manifested at behavioral or clinical levels. In the present study, EEG activity was recorded in 25 healthy participants and 30 amnestic MCI patients (17 sdaMCI and 13 mdaMCI) while they performed a Simon task. The ERPs associated with visuospatial (N2 posterior-contralateral - N2pc -) and motor (lateralized readiness potential - LRP -) processes were examined. The N2pc amplitude was smaller in participants with mdaMCI than in healthy participants, which indicated a decline in the correlates of allocation of attentional resources to the target stimulus. In addition, N2pc amplitude proved to be a moderately good biomarker of mdaMCI subtype (0.77 sensitivity, 0.76 specificity). However, the LRP amplitude was smaller in the two MCI groups (sdaMCI and mdaMCI) than in healthy participants, revealing a reduction in the motor resources available to execute the response in sdaMCI and mdaMCI patients. Furthermore, the LRP amplitude proved to be a valid biomarker (0.80 sensitivity, 0.92 specificity) of both amnestic MCI subtypes.

Aging and response interference across sensory modalities

Advancing age is associated with decrements in selective attention. It was recently hypothesized that age-related differences in selective attention depend on sensory modality. The goal of the present study was to investigate the role of sensory modality in age-related vulnerability to distraction, using a response interference task. To this end, 16 younger (mean age = 23.1 years) and 24 older (mean age = 65.3 years) adults performed four response interference tasks, involving all combinations of visual and auditory targets and distractors. The results showed that response interference effects differ across sensory modalities, but not across age groups. These results indicate that sensory modality plays an important role in vulnerability to distraction, but not in age-related distractibility by irrelevant spatial information.

Dissociation of preparatory attention and response monitoring maturation during adolescence

OBJECTIVE

Substantial brain development occurs during adolescence providing the foundation for functional advancement from stimulus-bound "bottom-up" to more mature executive-driven "top-down" processing strategies. The objective was to assess development of EEG markers of these strategies and their role in both preparatory attention (contingent negative variation, CNV) and response monitoring (Error Related Negativity, ERN, and Correct Related Negativity, CRN).

METHODS

CNV, ERN and CRN were assessed in 38 adolescents (18 girls), age 11-18 years, using a variation of a letter discrimination task.

RESULTS

Accuracy increased with age and developmental stage. Younger adolescents used a posterior attention network involved in inhibiting irrelevant information. Activity in this juvenile network, as indexed by a posteriorly-biased CNV and CRN decreased with age and advancing pubertal development. Although enhanced frontal CNV, known to be predictive of accuracy in adults, was not detected even in the older adolescents, top-down medial frontal response monitoring processes (ERN) showed evidence of development within the age-range studied.

CONCLUSIONS

The data revealed a dissociation of developmental progress, marked by relatively delayed onset of frontal preparatory attention relative to error monitoring.

SIGNIFICANCE

This dissociation may render adolescents vulnerable to excessive risk-taking and disinhibited behavior imposed by asynchronous development of component cognitive control processes.

Response-specific slowing in older age revealed through differential stimulus and response effects on P300 latency and reaction time

Older age produces numerous changes in cognitive processes, including slowing in the rate of mental processing speed. There has been controversy over the past three decades about whether this slowing is generalized or process-specific. A growing literature indicates that it is process-specific and suggests it is most dramatic at the interface where a stimulus input is translated into a response output. We tested this hypothesis using a task in which young and older adult males made either compatible or incompatible responses to the word LEFT or RIGHT shown briefly and variously located in a 4 row × 6 column matrix surrounded by # signs or by letters chosen randomly from the sets A-G or A-Z. Processing speed was measured using P300 latency and reaction time. Experimental effects on these two measures provided support for the hypothesis in revealing that stimulus identification processes were preserved, whereas processes related to translating a stimulus input into a designated response output and then selecting that response were compromised in the elderly.

Asymmetry in stimulus and response conflict processing across the adult lifespan: ERP and EMG evidence

Several studies have shown that conflict processing improves from childhood to adulthood and declines from adulthood to old age. However the neural mechanisms underlying this lifespan asymmetry were previously unexplored. We combined event-related potentials (ERPs) and electromyography (EMG) to examine lifespan changes in stimulus and response conflict processing using a modified Stroop task. We used a Stroop task that a priori dissociated stimulus and response conflict. Delayed P3b latency and increased amplitude revealed that middle age adults have a deficit in stimulus processing. Additionally a sustained P3a across frontal and central electrodes occurred only in middle age adults indicating the recruitment of frontal activity. Conversely, decreased lateralized readiness potential (LRP) amplitude and increased EMG activity in the incorrect hand in adolescents reveal protracted development of response processing into late adolescence. The N450, a measure of conflict processing, was found to be sensitive to both stimulus and response conflict. Altogether these results provide evidence for asymmetrical differences in stimulus and response conflict processing across adolescence, young adulthood and middle age.

The dissociation between early and late selection in older adults

Older adults exhibit a reduced ability to ignore task-irrelevant stimuli; however, it remains to be determined where along the information processing stream the most salient age-associated changes occur. In the current study, ERPs provided an opportunity to determine whether age-related differences in processing task-irrelevant stimuli were uniform across information processing stages or disproportionately affected either early or late selection. ERPs were measured in young and old adults during a color-selective attention task in which participants responded to target letters in a specified color (attend condition) while ignoring letters in a different color (ignore condition). Old participants were matched to two groups of young participants on the basis of neuropsychological test performance: one using age-appropriate norms and the other using test scores not adjusted for age. There were no age-associated differences in the magnitude of early selection (attend-ignore), as indexed by the size of the anterior selection positivity and posterior selection negativity. During late selection, as indexed by P3b amplitude, both groups of young participants generated neural responses to target letters under the attend versus ignore conditions that were highly differentiated. In striking contrast, old participants generated a P3b to target letters with no reliable differences between conditions. Individuals who were slow to initiate early selection appeared to be less successful at executing late selection. Despite relative preservation of the operations of early selection, processing delays may lead older participants to allocate excessive resources to task-irrelevant stimuli during late selection.

Distinct aging effects for two types of inhibition in older adults: a near-infrared spectroscopy study on the Simon task and the flanker task

The present study examined age-related changes in inhibitory processes among older and younger adults in the flanker and Simon tasks in terms of behavioral performance and prefrontal brain activity by functional near-infrared spectroscopy. The flanker task requires a quick identification of a central target in the presence of surrounding distracters, whereas the Simon task requires an individual to respond with left and right key presses to nonspatial features of the stimulus presented in the left and right locations. The reaction times of two age groups were longer under incongruent conditions than under congruent conditions in both tasks, indicating that the flanker effect (interference suppression) and the Simon effect (response suppression) were evident. In agreement with previous studies, the magnitude of the effect for the Simon task was greater for the older adults than for the younger adults, whereas the two groups showed equivalent flanker effects. The results suggest that older adults have difficulties in response inhibition, but not in stimulus interference suppression. Enhanced activity was found in different brain regions across the two tasks among the older adults. The older adults showed more activity in the superior and middle frontal gyri of the left hemisphere than younger adults in the flanker task; they showed more activity in the bilateral superior frontal gyri in the Simon task. These results suggest that the underlying mechanisms of the inhibition processes for the two tasks are distinct: they rely on different brain regions and have differential vulnerabilities to aging.

When compensation fails: attentional deficits in healthy ageing caused by visual distraction

Age related changes in frontal lobe functions are often related to attentional deficits that lead to increased distractibility by irrelevant stimuli. However, attentional functions have been reported not to decline in general with increasing age but simply be too slow to deal properly with distraction in time. Therefore older people might be able to compensate for distraction quite efficiently with sufficient processing time. Compensation, however, might fail when early perceptual processing is affected by distraction already. In the present study, a change in luminance or in orientation had to be detected in a sequence of two visual frames. Older participants showed reduced performance only when luminance and orientation changes were presented simultaneously at separate locations (perceptual conflict condition). Sensory ERP components were not overall altered with increasing age. Only in conflicting trials, a strong bias towards physically more salient information was observed. Additionally, older adults showed markedly delayed ERP-correlates of fronto-central control mechanisms in the conflict condition. The data indicate that processing deceleration cannot compensate for perceptual conflicts induced by mis-weighting of incoming information.

Compensation through increased functional connectivity: neural correlates of inhibition in old and young

With increasing age, people experience more difficulties with suppressing irrelevant information, which may have a major impact on cognitive functioning. The extent of decline of inhibitory functions with age is highly variable between individuals. In this study, we used ERPs and phase locking analyses to investigate neural correlates of this variability in inhibition between individuals. Older and younger participants performed a selective attention task in which relevant and irrelevant information was presented simultaneously. The participants were split into high and low performers based on their level of inhibition inefficiency, that is, the slowing of RTs induced by information that participants were instructed to ignore. P1 peak amplitudes were larger in low performers than in high performers, indicating that low performers were less able to suppress the processing of irrelevant stimuli. Phase locking analyses were used as a measure of functional connectivity. Efficient inhibition in both age groups was related to the increased functional connectivity in the alpha band between frontal and occipito-parietal ROIs in the prestimulus interval. In addition, increased power in the alpha band in occipito-parietal ROIs was related to better inhibition both before and after stimulus onset. Phase locking in the upper beta band before and during stimulus presentation between frontal and occipito-parietal ROIs was related to a better performance in older participants only, suggesting that this is an active compensation mechanism employed to maintain adequate performance. In addition, increased top-down modulation and increased power in the alpha band appears to be a general mechanism facilitating inhibition in both age groups.

Keeping focused: sustained spatial selective visual attention is maintained in healthy old age

A better understanding of age-related change in the attentional modulation of perceptual processing may help elucidate cognitive change. For example, increased cognitive interference due to inappropriate processing of irrelevant information has been suggested to contribute to cognitive decline. However, it is not yet clear whether interference effects observed at later stages, such as executive function or response selection, are caused by leaky attentional selection at early, sensory stages of processing. Here, we investigated attentional control of sensory selection by comparing younger and older adults' ability to sustain spatial selective attention to one of two centrally presented, overlapping rapid serial visual presentation (RSVP) letter sequences, one large and one small. These stimuli elicited separable steady-state visual evoked potentials (SSVEP), which provide an index of early visual processing for each stimulus separately and are known to be modulated by selective attention. The condition of most interest required participants to attend to the larger letters while ignoring the smaller letters, as these foveally presented irrelevant stimuli were expected to present the strongest interference. Although the rapid presentation rates made the task demanding, detection ability did not differ between young and older adults. Accordingly, attentional modulation of SSVEP amplitudes was found in both age groups. Neither the magnitude nor the cortical sources of these SSVEP attention effects differed between age groups. Our results thus suggest that in the current task, the effect of voluntary spatial attention on sustained sensory processing in early visual areas is maintained in healthy old age.

Attention network performance and psychopathic symptoms in early adolescence: an ERP study

Reaction time (RT) and event-related potential (ERP) measures were used to examine the relationships between psychopathic symptoms and three major attention networks (alerting, orienting, and executive attention) among a community sample of youth. Antisocial Process Screening Device (APSD; Frick and Hare 2001) total and subscale scores were negatively correlated with ERP measures of attentional alerting, indicating that youth with psychopathic symptoms had difficulty using warning cues to prepare for upcoming targets. APSD total scores were not related to performance on measures of orienting or executive attention, although weaker executive attention was found among youth with higher scores on the Impulsivity subscale. These findings support attention-based models of psychopathy and provide evidence of specific deficits in attentional alerting among youth with psychopathic traits. Deficiencies in attentional alerting may be related to noradrenergic functioning and may have cascading effects on higher order cognitive and affective processing.

Dissociation of motor and sensory inhibition processes in normal aging

OBJECTIVE

Age-related cognitive impairments have been attributed to deficits in inhibitory processes that mediate both motor restraint and sensory filtering. However, behavioral studies have failed to show an association between tasks that measure these distinct types of inhibition. In the present study, we hypothesized neural markers reflecting each type of inhibition may reveal a relationship across inhibitory domains in older adults.

METHODS

Electroencephalography (EEG) and behavioral measures were used to explore whether there was an across-participant correlation between sensory suppression and motor inhibition. Sixteen healthy older adult participants (65-80 years) engaged in two separate experimental paradigms: a selective attention, delayed-recognition task and a stop-signal task.

RESULTS

Findings revealed no significant relationship existed between neural markers of sensory suppression (P1 amplitude; N170 latency) and markers of motor inhibition (N2 and P3 amplitude and latency) in older adults.

CONCLUSIONS

These distinct inhibitory domains are differentially impacted in normal aging, as evidenced by previous behavioral work and the current neural findings. Thus a generalized inhibitory deficit may not be a common impairment in cognitive aging.

SIGNIFICANCE

Given that some theories of cognitive aging suggest age-related failure of inhibitory mechanisms may span different modalities, the present findings contribute to an alternative view where age-related declines within each inhibitory modality are unrelated.

The development of inhibitory control: an averaged and single-trial Lateralized Readiness Potential study

Inhibitory control (IC) is an important contributor to educational performance, and undergoes rapid development in childhood. Age-related changes in IC were assessed using an in-depth analysis of reaction time, the Lateralized Readiness Potential (LRP), and other event-related potential (ERP) measures to control for speed of processing. Five-year-olds, 8-year-olds and adults completed an adapted Stroop task. Both reaction time and ERP results suggest that IC does develop in this age range, over and above changes in speed of processing. The LRP identified two processes that contribute to IC. These processes develop at different rates--an early process, involving how the conflict is initially responded to is mature by age 5, while a later process, involving how the conflict is overcome is still developing after 8 years of age. We propose that these early and late processes reflect interference suppression and response inhibition, respectively. Further, a single-trial analysis of the LRP in the incongruent condition provides evidence that the LRP is consistent across trials and functionally similar in each age group. These results corroborate previous findings regarding the development of IC, and present a new and useful tool for assessing IC across development.

Is flanker-based inhibition related to age? Identifying specific influences of individual differences on neurocognitive variables

Researchers frequently attempt to identify the specific neurocognitive processes that might be responsible for differences in performance associated with neurological status or other individual difference characteristics by administering two or more conditions of an experimental task to different groups of participants, and focusing on the group-by-condition interaction as the primary outcome of interest. Three limitations of this approach are discussed, and an alternative analytical method is proposed to overcome the limitations. The method is demonstrated in analyses of data from 10 cognitive tasks in two independent studies, including two flanker tasks which are often used to assess aspects of inhibition.

Age-related delay in information accrual for faces: evidence from a parametric, single-trial EEG approach

Background

In this study, we quantified age-related changes in the time-course of face processing by means of an innovative single-trial ERP approach. Unlike analyses used in previous studies, our approach does not rely on peak measurements and can provide a more sensitive measure of processing delays. Young and old adults (mean ages 22 and 70 years) performed a non-speeded discrimination task between two faces. The phase spectrum of these faces was manipulated parametrically to create pictures that ranged between pure noise (0% phase information) and the undistorted signal (100% phase information), with five intermediate steps.

Results

Behavioural 75% correct thresholds were on average lower, and maximum accuracy was higher, in younger than older observers. ERPs from each subject were entered into a single-trial general linear regression model to identify variations in neural activity statistically associated with changes in image structure. The earliest age-related ERP differences occurred in the time window of the N170. Older observers had a significantly stronger N170 in response to noise, but this age difference decreased with increasing phase information. Overall, manipulating image phase information had a greater effect on ERPs from younger observers, which was quantified using a hierarchical modelling approach. Importantly, visual activity was modulated by the same stimulus parameters in younger and older subjects. The fit of the model, indexed by R², was computed at multiple post-stimulus time points. The time-course of the R² function showed a significantly slower processing in older observers starting around 120 ms after stimulus onset. This age-related delay increased over time to reach a maximum around 190 ms, at which latency younger observers had around 50 ms time lead over older observers.

Conclusion

Using a component-free ERP analysis that provides a precise timing of the visual system sensitivity to image structure, the current study demonstrates that older observers accumulate face information more slowly than younger subjects. Additionally, the N170 appears to be less face-sensitive in older observers.

Neurobehavioral effects during exposures to propionic acid--an indicator of chemosensory distraction?

The chemosensory effects of propionic acid (PA) in humans have not been conclusively studied and there is no established occupational exposure limit (OEL) in Germany. In addition to sensory irritation caused by PA, it was hypothesized that the annoying odor of PA might interfere with the performance results. There were 23 consenting healthy participants (12 female, 11 male) in the group studied. They were exposed for 4 h to PA in concentrations of 0.3, 5 and 10 ppm in a cross-over design. During these exposures, performance was recorded with four cognitive tests measuring response-inhibition, working memory, set-shifting, and divided attention. Odor annoyance, other chemosensory sensations, and acute symptoms were assessed before, during, and after exposure with standardized rating scales. Moderate odor annoyance and weak sensory irritation were reported during 5 and 10 ppm exposure conditions. The different levels of exposure to PA had no impact upon the results of three out of the four behavioral tests. The difficulties of the task were reflected in the results. However in the fourth, which was the response-inhibition task, there was significant increase in the error rates which corresponded to the exposure levels. Results from previous experiments suggested high odor annoyance at the investigated concentrations. Our findings showed that odor annoyance and reported sensory irritations were low. In conclusion, the hypothesis of a distractive effect due to the malodor of PA could not be confirmed. Only in concentrations as high as 10 ppm acute PA exposure affected the response accuracy of one of the four neurobehavioral task. For other more annoying substances, a neurobehavioral effect influenced by an indirect mechanism of resources competition is still conceivable.

[Cognitive competence of older workers]

The article provides a short overview on cognitive strengths and weaknesses of older workers. The older people who are under the age of 65 years already exhibit changes in performance and neurophysiological measures in laboratory tasks that test fluid intelligence. Apart from deficits, the physiological data of the older people show clear evidence for compensatory strategies. Cognitive performance on the current job is usually less impaired. This can be explained by practice, learning, and selection, which are, however, often linked with higher effort. The cognitive competence of older employees varies exorbitantly, which is due to the influence of various factors like education, lifestyle, and in particular the type of work. Thus, the cognitive competence of older employees can be preserved and possibly even enhanced by changes in the work situation as well as by individual training procedures such as cognitive training.

Effects of aging, Parkinson's disease, and dopaminergic medication on response selection and control

We examined effects of short-term and long-term dopaminergic medication in Parkinson's disease on conflict monitoring or response selection processes. These processes were examined using event-related potentials (ERPs), while subjects performed a stimulus-response (S-R) compatibility task. An extended sample of young and elderly controls, Parkinson's disease patients with a medication history (PDs) and initially diagnosed, drug-naïve de novo PD patients (de novo PDs) were enrolled. Both PD groups were measured twice (on and off-medication or before and 8 weeks after medication onset). The results show that dopaminergic intervention selectively reduced the pathologically enhanced response selection in compatible S-R relations. This medication effect was already evident after short-term treatment, not differing from long-term treatment and performance in elderly controls. Contrary, age-related attenuations of the N2 in incompatible S-R relations, probably reflecting impaired conflict processing or response control, are unaffected by medication. The results suggest that compatible and incompatible S-R relations demand different neuronal mechanisms within the basal ganglia, as only the former are affected by agonizing the dopaminergic system.