Stefan Berti

Working memory controls involuntary attention switching: evidence from an auditory distraction paradigm

One function of working memory is to protect current mental processes against interference. In contrast, to be able to react flexibly on unpredictable environmental changes working memory should not totally be encapsulated from processing task unrelated information; that is, it should remain distractible. By manipulating the task load of the primary task in an auditory distraction paradigm we investigated how these opposing functions are coordinated by working memory. The behavioural results show that distraction effects were still present but reduced markedly with higher task demands. This suggests that working memory exerts some control over involuntary attention. In addition, event‐related brain potentials related to the different processing stages reveal that the preattentive change detection system underlying distraction was not modulated by task demand whereas distraction per se was. The present data suggest that working memory is able to coordinate the maintenance of distractibility and the focus on the task at hand.

A comparison of auditory and visual distraction effects: behavioral and event-related indices.

Infrequent task-irrelevant deviations in the frequency of a tone may distract our attention away from the processing of task-relevant tone duration. The distraction obtained in the auditory paradigm is reflected in prolonged reaction times in duration discrimination and in P3a. The P3a is followed by a late negative component, which may be related to a re-orienting process following distraction (RON, re-orienting negativity). The present study aimed at comparing effects of the auditory and a corresponding visual distraction paradigm. Distraction elicited a deviance-related negativity which revealed a modality-specific distribution. It was followed by P3a (350-ms post-stimulus) and by RON (500-ms post-stimulus). RON did not occur with long-duration visual stimuli indicating a difference in visual and auditory distraction. Moreover, the results suggest that in both tasks irrelevant deviants were detected by modality-specific processes which caused an attention shift.

Bottom-Up Influences on Working Memory: Behavioral and Electrophysiological Distraction Varies with Distractor Strength

The present study investigates bottom-up effects serving the optimal balance between focusing attention on relevant information and distractibility by potentially significant events outside the focus of attention. We tested whether distraction, indicated by behavioral and event-related brain potential (ERP) measures, varies with the strength of task-irrelevant deviances. Twenty subjects performed a tone-duration discrimination task (200 or 400 ms sinusoidal tones presented equiprobably). The stimuli were presented with frequent standard (p = 0.84; 1000 Hz) or infrequent deviant (p = 0.16) pitch. These task-irrelevant pitch changes consisted in a frequency increase/decrease of 1%, 3%, 5%, or 10%. Each of them resulted in prolonged reaction times (RT) in the duration discrimination task and elicited the MMN, P3a, and RON components of the ERP. Importantly, these measures did increase as a function of pitch deviance. Separating the individual trials on the 1% deviation level into trials with and without RT prolongation, i.e., behavioral distraction effect, revealed that both subgroups had similar MMN, but P3a and RON were confined to the trials with RT prolongation. Results are interpreted within a model relating preattentive deviance detection, distraction, and working memory.

The development of involuntary and voluntary attention from childhood to adulthood: a combined behavioral and event-related potential study.

OBJECTIVE This study investigated auditory involuntary and voluntary attention in children aged 6-8, 10-12 and young adults. The strength of distracting stimuli (20% and 5% pitch changes) and the amount of allocation of attention were varied. METHODS In an auditory distraction paradigm event-related potentials (ERPs) and behavioral data were measured from subjects either performing a sound duration discrimination task or watching a silent video. RESULTS Pitch changed sounds caused prolonged reaction times and decreased hit rates in all age groups. Larger distractors (20%) caused stronger distraction in children, but not in adults. The amplitudes of mismatch negativity (MMN), P3a, and reorienting negativity (RON) were modulated by age and by voluntary attention. P3a was additionally affected by distractor strength. Maturational changes were also observed in the amplitudes of P1 (decreasing with age) and N1 (increasing with age). P2-modulation by voluntary attention was opposite in young children and adults. CONCLUSIONS Results suggest quantitative and qualitative changes in auditory voluntary and involuntary attention and distraction during development. The processing steps involved in distraction (pre-attentive change detection, attention switch, reorienting) are functional in children aged 6-8 but reveal characteristic differences to those of young adults. In general, distractibility as indicated by behavioral and ERP measures decreases from childhood to adulthood. SIGNIFICANCE Behavioral and ERP markers for different processing stages involved in voluntary and involuntary attention reveal characteristic developmental changes from childhood to young adulthood.

Distraction effects in vision: behavioral and event-related potential indices.

Evidence is presented which shows that slight changes in serially presented visual input can be detected automatically and may result in behavioral distraction. In two experiments, reaction times on a two-alternative, forced-choice duration discrimination task were prolonged in trials where a task-irrelevant change in the location of the stimulus occurred. The P1 and N1 components of the event-related potential were enhanced in such trials. However, electrophysiological and behavioral effects were not affected when the duration discrimination was made more difficult and the N1 amplitude increase and RT prolongation were confined to situations where task-irrelevant location changes were infrequent. Thus, these effects most probably reflect pre-attentive change detection and subsequent distraction in vision, whereas the P1 effect is probably due to spatial eccentricity.

Cognitive control after distraction: Event‐related brain potentials (ERPs) dissociate between different processes of attentional allocation

Attentional reallocation after a distracting event is an important function of cognitive control. This process is tapped by the reorienting negativity (RON) event-related brain potential. It was argued that the RON reflects orientation of attention to relevant information in working memory. To test this hypothesis participants performed an auditory duration discrimination task. The stimuli were presented in a frequent standard or a rare deviant pitch with deviants resulting in behavioral distraction. Participants accomplished this task under two conditions: In the refocus condition participants were asked to respond to every stimulus; in the reorient condition participants were instructed to ignore deviant stimuli and omit a reaction. The results suggest that different functions of attentional allocation are reflected by two RON subcomponents: the fast orientation of the focus of attention in working memory and a subsequent poststimulus evaluation process.

Examining task-dependencies of different attentional processes as reflected in the P3a and reorienting negativity components of the human event-related brain potential

Unexpected changes in task-irrelevant auditory stimuli are capable to distract processing of task-relevant visual information. This effect is accompanied by the elicitation of event-related potential (ERP) components associated with attentional orientation, i.e. P3a and reorienting negativity (RON). In the present study we varied the demands of a visual task in order to test whether the RON component -- as an index of attentional reorientation after distraction -- is confined to a semantic task requiring working memory. In two ERP experiments we applied an auditory-visual distraction paradigm in which subjects were instructed to discriminate visual stimuli preceded by a task-irrelevant sound, this being either a standard tone (600 Hz, 88%) or a deviant tone (660 Hz, 12%). The visual stimuli were numbers which had to be judged on basis of a semantic (odd or even) or physical feature (either size or colour). As expected, deviance related ERP components namely the mismatch negativity (MMN), P3a, and RON were elicited. Importantly, the RON was affected by the variation of the task: within the semantic task an early RON and within the physical task a late RON was obtained. These results suggest that the RON component reflects two functionally distinct processes of attentional allocation after distraction: refocusing on task-relevant information on the working memory level, and general reorientation of attention, e.g. preparation for the upcoming task.

Auditory distraction with different presentation rates: an event-related potential and behavioral study

OBJECTIVE The present study addresses the question of whether behavioral and electrophysiological effects obtained with the auditory distraction paradigm proposed by Schröger et al. [Clin Neurophysiol 2000;111:1450] depend on the timing of stimulus occurrence. METHODS Subjects had to discriminate the duration of tones. Occasionally, task-irrelevant frequency changes were used as distractors. In 3 experiments the stimulus onset asynchrony (SOA) was manipulated: In Experiment 1, SOAs of 1500, 2000 and 3000 ms were used in separate blocks; in Experiment 2, 5 different SOA of lengths between 1300 and 2500 ms were used within the blocks; in Experiment 3, a constant SOA of 1400 ms was compared with a SOA of random lengths between 1300 and 1500 ms. Performance data was analyzed for distraction effects. Event-related potentials (ERPs) were examined for deviance-related components, i.e. the mismatch negativity (MMN), the P3a and the re-orienting negativity (RON). RESULTS Behavioral distraction effects were obtained in all experimental conditions. The electrophysiological data show MMN, P3a and RON for the deviating tones in all experimental conditions as well. CONCLUSIONS The behavioral and electrophysiological deviance-related effects were not sensitive to the SOA manipulations. Therefore, the timing of the presentation can be adjusted to the proficiency level of the population to be tested without loosing the distraction effects.

Task relevance and recognition of concealed information have different influences on electrodermal activity and event-related brain potentials.

This study aimed at differentiating between memory- and task-related processes and their correlates on the electrodermal and electrocortical level during information concealment. Variations of the Guilty Knowledge Test were implemented in two experiments while we measured skin conductance responses (SCRs) and event-related brain potentials. P300 amplitudes were specifically enhanced for items requiring a deviant behavioral response but they were not sensitive to concealed knowledge. In contrast, N200 amplitudes differed between memorized and irrelevant items in both experiments. SCR measures reflected a combined influence of task relevance and probe recognition, and they provided incremental validity above N200 amplitudes. These results suggest that the P300 mainly reflects task relevance in the given experimental setting whereas the N200 amplitude is sensitive to previously encoded information and potentially linked to response monitoring processes.

Event-related brain potentials dissociate visual working memory processes under categorial and identical comparison conditions

Event-related potentials (ERPs) have been successfully employed to examine the functional and neuronal characteristics of working memory processes. In the present study, we examined the ERP waveforms in a delayed matching task to examine the cognitive processes underlying category and identity comparison and the effects of stimulus complexity. Subjects had to decide whether two visual stimuli are (a) physically identical (identical comparison condition, IC) or (b) identical, irrespective of their orientation (categorial comparison condition, CC). The stimuli were structured five-point patterns, which varied in complexity. For the ERPs elicited during the 1500 ms retention interval, the following pattern of results was obtained: Stimuli in the CC-condition elicited larger P300 components than in the IC-condition. In the IC-condition, the P300 was followed by a broadly distributed negative slow wave. Moreover, complex patterns elicited a posteriorily distributed negativity at 350 ms (N350), whereas the less complex patterns gave rise to a fronto-centrally distributed slow wave that started around 500 ms. These results suggest that S1 was more elaborately processed in the CC-condition, while the more complex figures were associated with an early classification process during the retention interval.