Neurocognitive correlates of distraction processes caused by events related to delayed intentions

Transcription

1 Revista de Motivación y Emoción 2012, 1, Enrique Pérez, Juan J. G. Meilán, Juan Carro & José M. Arana Universidad de Salamanca Neurocognitive correlates of distraction processes caused by events related to delayed intentions Keywords Intention Attentional demand Prospective memory ERP Abstract The aim of the present study is to obtain behavioral and ERP correlates of distraction that occurs in a digit classification task due to interruptions caused by spontaneous retrieval of delayed intentions. ERPs were recorded from 62 scalp sites in a task that assesses distraction using three types of stimuli (standard meaningless distracting stimuli, neutral words, and cue words related to a delayed intention). Behavioral analyses revealed significant differences in response times between intentional and standard stimuli and between neutral and standard stimuli. The analysis of the ERP showed that P3 amplitude was significantly larger for intentional stimuli than for the other two types of stimuli and that P680 amplitude was significantly larger for the intentional stimuli than for the standard stimuli. The results showed that, consistent with the model of spontaneous retrieval, intentionally distracting stimuli are processed in a distinct way as they capture specific attentional resources in an involuntary way. Prospective Memory (PM) is the recall and realization of delayed intentions (for example: "I have to buy bread on the way home") (McDaniel & Einstein, 2007; Arana, Meilán, & Pérez, 2008). Remembering an intention requires the interruption of the current task being performed (the background or ongoing task) and the completion of the intended action (the prospective memory task). On occasions, attention must be controlled at the right time for the correct performance of the intended action (e.g. "on the next street I think there is a bakery ), because they are tasks that must be performed soon after formation of intention. On other occasions in which the delay between formation of an intention and the opportunity to carry it out is longer (for example when we see a coworker and we remember we have to give him a message), remembering to perform the intended action depends on awareness of an event that provides a cue that indicates the intended response is appropriate. In the latter case it is necessary to change the focus of attention from the background task to the intentional task. Several theories have been postulated to try to explain how the attention is switched from the ongoing task to the delayed intention (for a review see McDaniel & Einstein, 2000, 2007). Authors working from the attentional monitoring framework argue that the switch of focus from an activity in which we are immersed to a delayed intention is a strategic and voluntary process involving cognitive demands (Craik, 1986; Marsh & Hicks, 1998; Smith, 2003) and therefore have an attentional cost (de Jong, 1997; Marsh, Hicks, Cook, Hansen, & Pallos, 2003; Smith, 2003). Smith have provided data that show that the execution of an event based PM task slows down the processing of ongoing tasks (Smith, Hunt, McVay, & McConnell, 2007), which demonstrate that resources are used to monitor for PM events. On the other hand, spontaneous retrieval theories (Einstein & McDaniel, 1996; Guynn, McDaniel, & Einstein, 2001) argue that people rely on spontaneous attentional processes to retrieve their intentions when faced with the events of a PM task. According to this perspective, PM cues or external events become essential in the automatic and spontaneous retrieval of an intention (Einstein, McDaniel, Thomas, Mayfield, Shank, Morrisette, & Breneiser, 2005), as they trigger memories of the delayed intention. This shift of attention from the main activity to the delayed intention is appropriate when it is time to perform the intended task. However, when REME, ISSN 2012, All Correspondence can be sent to the author, Enrique Pérez Sáez, University of Salamanca, Department of Psychology, Avda. de la Merced, , E Salamanca, Spain Acknowledgements: This research was supported by grants from La Caixa and Castilla & León Government. 12

2 E. Pérez et al. Distraction processes caused by delayed intentions 13 it is not the right time to perform the intention this shift of attention is an involuntary distraction process from the activity being performed by the participant. Einstein and his colleagues found that the presence of a PM event, even in contexts where the subjects must not perform the PM task, can involuntary trigger retrieval processes and these should slow down (interfere with) the speed of making a lexical decision. (Einstein et al., 2005, Experiment 5). This description of processes seems to match people s introspective impression that, sometimes, the intended action pops into their mind (McDaniel & Einstein, 2000; Meilán, 2008). It seems clear that in order to spontaneous retrieval of an intention occurs in the presence of a related event, the intention must be in a special activation state that allows a quick access to conscious. This is what intention superiority effect studies (Goschke & Kulh, 1993) have shown: intentions enjoy special memory storage status and are activated permanently since codification to performance, through retention interval. This state of higher activation makes people more sensitive to retrieval cues (Mäntylä, 1996; Yaniv & Meyer, 1987) and allows spontaneous retrieval of the intention even when the intended action must not be performed, like during the retention interval. As we have said before, the retrieval of an intention when it is not the right time to perform it is a distraction that would impair performance on other tasks or cognitive processes in course. Given the limitations of behavioural studies in explaining the underlying processes that occur during a PM task (in particular during the retention interval), we believe it would be useful to study event-related potentials (ERP) elicited by stimuli related to intentions, since they can provide online indexes of the processes triggered by the onset of a intentional cue. Furthermore, ERP waveforms may show differences in cognitive processing even when the behavioural results do not present such differences. Investigations that have used ERP to study the neural correlates of PM tasks have focused on the analysis of ERP modulations that are differentially related to the detection, at the appropriate time, of PM cues and processes after the recovery of the intention. A series of ERP experiments conducted by West and his students has shown two consistent patterns of neural activity associated with PM across a variety of ongoing activities (semantic similarity tasks, N-back tasks ) and a variety of PM targets (a particular word, a particular letter case, or a particular colour of type font) (West & Krompinger, 2005). The two ERP patterns associated with PM are termed N300 and prospective positivity. The N300 component, recorded at occipitoparietal electrodes between ms after the onset of the PM event (West, Herndon, & Crewdson, 2001; West & Ross-Munroe, 2002; West, Herndon, & Ross-Munroe, 2000), was associated with the detection of PM events (West & Ross-Munroe, 2002) and also was associated with PM cue monitoring (Chen, Huang, Yang, Ren, Chen, & Yue, 2007). The prospective positivity component is a sustained positivity over the parietal region between 400 and 1200 ms after the onset of the PM event (West et al., 2001) and has been associated with retrieval of the intention from memory (West & Ross-Munroe, 2002) and more recently with postrecovery processes that could be related with the need to co-ordinate the ongoing task and the prospective task once the intention has been retrieved (West & Krompinger, 2005). The parietal distribution of the prospective positivity bears some resemblance to the topography of the P3 component that is associated with target categorization (Kok, 2001) and the recognition oldnew effect that is associated with the retrieval of a previous episode from memory (Rugg, 1995). However, dissociations have been found between P3 and prospective positivity components in PM tasks (West & Wymbs, 2004; West, Bowry, & Krompinger 2006). These studies do not address the question of whether intentional stimuli automatically capture attentional resources, as argued by spontaneous retrieval theories. In this study we aimed to examine the processes of attention involved in the spontaneous retrieval of delayed intentions, but in moments that are inadequate to perform the intended action: during the retention interval of the intention. We tried to determine whether intentions are automatically retrieved outside the appropriate time of task execution. For this we examined whether the events related to an intention involuntarily capture attention during the retention interval. Our first hypothesis was that distractors related to delayed intentions will produce greater distraction than neutral distractors. The spontaneous retrieval of an intention resulting from the appearance of a distractor related to a prospective task will have a greater interference effect on the execution of the main task (see Einstein et al., 2005, Experiment 5) than those produced by other types of events both significant

3 14 Revista de Motivación y Emoción 2012, 1, pp and meaningless, but not related to an intention. Such a result would provide additional evidence for the occurrence of spontaneous retrieval of intentions processes. Additionally, we aimed to obtain ERP correlates of distraction that occurs in the main task due to interruptions caused by spontaneous retrieval of delayed intentions. Therefore, ERP was incorporated into this experiment to assess cognitive mechanisms underlying task interference from delayed intentions. This allowed analysis of involuntary and automatic changes in focus of attention from the main task to the secondary task. We expected to obtain differences in the amplitude of the target-related ERP components depending on the distracting stimuli previously presented. Concretely: a) larger P3 amplitudes after presenting distracting word (both neutral and related to delayed intentions) compared to standard distractors (string of letters); b) if prospective events automatically change the focus of attention, we expected differences in the amplitude of the ERP waveforms between neutral distractors and distractors related to delayed actions, most probably in the time intervals other studies have reported prospective memory effects, that is, 300 ms onwards. To achieve our aims we have used a method adapted from auditory distraction studies (see Escera et al., 1998) in which subjects are asked to focus on a digit classification task while ignoring the occurrence of irrelevant sounds that occur before each visual stimulus. Behavioural results from these studies shows that novel sounds increase reaction time and the number of incorrect answers in the classification task, which demonstrates that novel sounds produce greater distraction than standard ones; in addition, significant novel sounds produce greater distraction than non-significant novel ones (Escera et al., 2003). Also these authors showed that deviant and novel sounds not only affected to the auditory potentials, but also to the ERP components of the stimuli which were relevant for the task, that is, the visual ERP. Concretely, they found that the deviant and novel sounds enhanced the visual P3 amplitude, and therefore, significant (although irrelevant) stimuli automatically modulated the amplitude of the target-related ERP components. We used visually presented standard non-words (e.g., aaaaa ) and words (e.g., "bell") that are related to actions (e.g., "ring the bell") for distracting stimuli. These distracting words could be related to a neutral action (an action not associated to an instruction) or related to an action that is delayed (an action associated with an instruction to perform it later). To quantify the interference effect, we examined the response latency to digit classification task stimuli and analysed the ERP parameters involved in the distraction caused by stimuli either associated with a delayed task or not. Methods Participants From an initial sample of 17 university students, 14 subjects who presented a sufficient number of epochs free of artefacts, were selected as participants (11 females and 3 males) ranging in age between 20 and 27 years and a mean age of 23.6 years. All participants were healthy, with normal or corrected-to-normal visual acuity, self-reported right-handedness, with no history of neurological or psychiatric disorder, and no medication during the 4 weeks prior to the study. The study received prior approval by the local ethical review board. All participants were asked to refrain from smoking or drinking stimulant drinks for at least 2 h before the session and did not report fatigue due to insufficient sleep and gave their informed consent prior to their inclusion in the study. None of the participants was previously familiar with the protocols used in the study. Procedure Each participant completed a training block for the principal task and an experimental block with the same task. The training block for the principal task consisting in digit classification (number 2 to 9); numbers appeared in the centre of the screen and the subject had to press "2" for even numbers and "1" for odd numbers. In all cases the key was pressed with the dominant hand. The stimuli were numbers on a white background, using the Courier New font with a size of 18 points that were shown on a 19-inch screen at a distance of 50cm from the subjects. After the training block, the subjects learned a series of five independent actions (List A or B depending on the previous randomisation, -see table 1- ). The participants were told that these tasks were to be performed at the end of the session (formation of delayed intentions). After learning the tasks, they performed the experimental block which consisted of 400 trials with the appearance of distracting stimuli: Before the digit appeared an event occurred during 200ms that on 80% of the

4 E. Pérez et al. Distraction processes caused by delayed intentions 15 trials had a "standard" distractor ( aaaaaa ); 10% of the trials had a neutral distractor (the 5 words from a list that the subject had not learned, for example, whistle ); the other 10% of the trials had an "intentional" distractor (a keyword from the list of tasks that the subject had to perform later, for example, clap ). Each trial (see figure 1) consisted of a fixation point (500 ms), immediately followed by a distractor stimulus (200 ms), followed by the appearance of the digit between 2 and 9 (200 ms) and a screen that remain blank until the subject responded (maximum 2800 ms). Standard Distractor (80%) Neutral / Intentional Distractor (20%) + aaaaaa 500 ms 200 ms + toser Fixation Point Distractor Time ms 2800 ms 8 Number Mask Figure 1. Scheme of a trial of the experimental task with standard distractor (left) and with neutral or intentional distractor (right). Each distractor appeared eight times during the block, once with each number from 2 to 9. In the instructions to the subject they were asked to pay no attention to the distractors. The participants were instructed to ignore the distractors and focus on the numerical classification task and perform it as quickly and correctly as possible. Once the test was finished, the participants completed a test of recognition of the actions that they had learned and performed intended actions. Table 1. List of actions used in the experiment Action List A Snap your Fingers Ring the door bell Chime the bell Whistle EEG recording Clear your throat Action List B Clap Play a whistle Play a guitar Play a drum Cough Electroencephalographic activity was recorded at 62 tin electrodes inserted in a cap (Fp1, Fpz, Fp2, AF3, AF4, F7, F5, F3, F1, Fz, F2, F4, F6, F8, FT7, FC5, FC3, FC1, FCz, FC2, FC4, FC6, FT8, T3, C5, C3, C1, Cz, C2, C4, C6, T4, TP7, CP5, CP3, CP1, CPz, CP2, CP4, CP6, TP8, T5, P5, P3, P1, Pz, P2, P4, P6, T6, PO9, PO7, PO3, POz, PO4, PO8, PO10, O1, Oz, O2, A1, A2), in line with the International System, referenced to an average reference and with frontopolar ground. The EEG signal was passed through a Hz (24 db/octave slope) analog bandpass filter and amplified before being sampled at 250 Hz. Simultaneously with EEG recordings, an ocular movement (EOG) recording was obtained with two electrodes located supra- and infraorbitally to the right eye (VEOG) and two other electrodes at the lateral angle of each eye (HEOG). All impedances were maintained below 5 ko. After signal storage, ocular artifacts were corrected off-line using the algorithm of Gratton, Coles, & Donchin (1983); the EEG was segmented and 1200 ms epochs were extracted (with 200 ms of pre-stimulus baseline) associated with each type of distractor (Standard, Neutral, and Intentional). The epochs that were contaminated by excessive eye movement or that exceeded + 80 µv were automatically rejected and excluded from subsequent averaging (8%). The signal was digitally filtered between Hz and then a linear trend correction was performed. Finally, baseline correction was made using the 200 ms pre-stimulus and the epochs were averaged. Data Analysis In regard to the performance data in the digit categorization task, the measure used was the latency time of correct categorizations. With the

5 16 Revista de Motivación y Emoción 2012, 1, pp latencies obtained in each test we obtained the average for each participant depending on the type of distractor prior to the valuation of the digit (see table 2; Intentional, Neutral and Standard). The accuracy rate of the task is not reported because of the absence of any effects, due to a ceiling effect. As regards to ERP recordings, we have obtained for each participant three averaged ERP waveforms (one for each distractor stimulus: Standard, Neutral and Intentional). The focus of interest in this study has been three components, a negative deflection at about 300 ms (N300), after the distractor stimulus and 100 ms after the target stimulus; a positive complex in the ms interval (P3), ms after the target stimulus; and a late positive component at about 680 ms (P680), 480 ms after the target stimulus. The latency and amplitude of N300 and P680 was measured at the maximum negative and positive peak with respect to baseline at F7, Fz, F8, T3, Cz, T4, T5, Pz, T6 in the ms, and the ms intervals, respectively. In addition, P3 mean amplitude was measured in the ms interval at the same electrode sites cited above. Statistical analyses To compare the latencies of the three types of distractor we used repeated-measures analysis of variance (ANOVA) with one within-subject factor, Type of Distractor (levels: Standard, Neutral, intentional). To investigate the factors affecting the amplitude and latency of N300, and P3 and P680 mean amplitudes in the intervals studied, in the different stimulus categories and at the different electrode positions, we carried out repeated ANOVAs with three within-subject factors, Stimulus Category (with three levels; Standard, Neutral, and Intentional), Position (with three levels: Left, Midline, and Right) and Region (with three levels: Anterior [F7/F8], Central [T3/T4], and Posterior [T5/T6]). The Greenhouse-Geisser correction was applied to degrees of freedom in all cases in which the condition of sphericity was not met. Statistical differences (p 0.05) were followed by post-hoc pair-wise multiple comparisons (Bonferroni adjustment). All statistical analyses were performed using the statistics package SPSS for Windows (version 15.0). Results Behavioral data The average latency of categorization of experimental block was 649 ms (see table 2). ANOVA showed significant differences F(2, 26)=9.931, MSE= , p<0.001 depending on the previous distractor. In pair-wise comparison between the different types of distractors, significant differences in latency times between Standard and Neutral distractors (Bonferroni adjustment, p= 0.011) and between standard and intentional distractors (Bonferroni adjustment, p< 0.01) were found, but not between Neutral and Intentional distractors (Bonferroni adjustment, p= 1.00), with longer latencies for Intentional and Neutral stimulus than for Standard stimulus. Table 2. Average Latency and accuracy rate in the digit categorization task depending on the type of distractor (Standard, Neutral or Intentional). Categorization Latencies Accuracy rate Standard Neutral Intentional Standard Neutral Intentional 640 (127) 681 (137) 686 (135).95 (.02).94 (.05).95 (.03) ERP data As can be seen in Figure 2, the ERP waveforms showed, at about 300 ms after distractor stimulus presentation (and 100 ms after the visual target presentation), a negative wave with the largest amplitudes at frontal-central electrode sites, N300; in the ms interval after the distractor stimuli (and ms after the target stimulus), a positive complex is observed, P3, with largest amplitudes at parietal electrode sites. In addition, a positive slow wave, P680, was observed in the interval after the distractor stimuli (and ms after the target stimulus), showing the largest amplitudes at frontal-central electrode sites.

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7 E. Pérez et al. Distraction processes caused by delayed intentions 17 Figure 2. Grand average ERP waveforms for the three distractor stimuli: Intentional (continuous thick line), Neutral (dashed line), and Standard (continuous thin line). The vertical dashed lines indicate the onset of distractor (0 ms) and target (200 ms) stimuli.

8 18 Revista de Motivación y Emoción 2012, 1, pp N300 The repeated measures ANOVA (Stimulus Category, Position, and Region) showed, for N300 latency, a significant effect of the factor Region F(2, 26)=13.78, MSE=956.70, p 0.001, as latencies were shorter at posterior than at central (p=0.011) and anterior (p=0.001) electrode sites. The repeated measures ANOVA (Stimulus Category, Position, and Region) showed, for N300 amplitude, a significant effect of the interaction Stimulus Category x Region F(4, 52)=3.7, ε=0.588, MSE=3.80, p=0.03, as frontal electrode sites presented larger amplitudes than posterior electrode sites (p=0.044) only for the standard stimuli. The analyses also revealed a significant effect of the interaction Stimulus Category x Position F(4, 52)=3.81, ε=0.822, MSE=2.13, p=0.014, as larger amplitudes were found at the midline than at left electrode sites for the standard (p=0.025) and the neutral stimuli (p=0.014), and a significant effect of the interaction Region x Position F(4, 52)=4.02, ε=0.770, MSE=4.19, p=0.013, as frontal locations showed larger amplitudes than central locations at the midline electrode sites (p=0.005), and midline locations showed larger amplitudes than left locations at frontal electrode sites (p=0.006). P3 Regarding the P3 mean amplitude, the repeated measures ANOVA (Stimulus Category, Position, and Region) detected a significant effect of the factor Stimulus Category F(2, 26)=3.66, MSE=4.08, p=0.04, with larger amplitudes for Intentional than for Standard stimuli (p=0.005), and a significant effect of Position F(2, 26)=14.27, MSE=20.72, p 0.001, as the midline electrode sites showed larger amplitudes than the left (p=0.026) and the right (p=0.001) electrode sites. In addition, the ANOVA detected a significant effect of the interaction Stimulus Category x Region F(4, 52)=5.36, ε=0.693, MSE=2.28, p=0.005, as amplitudes were significantly larger for Intentional than for Standard stimuli at central (p=0.001) and posterior (p<0.001) electrode sites, and marginally larger for Intentional than for Neutral stimuli (p=0.057) at posterior electrode sites, and significantly larger at central than at anterior electrode sites (p=0.025) only for Intentional stimuli. Finally, the ANOVA showed a significant effect of the interaction Region x Position F(4,52)=17.43, ε=0.664, MSE=5.10, p 0.001, with larger amplitudes at posterior (p=0.002) and central (p<0.001) than at anterior locations in the midline electrode sites, larger amplitudes at midline than at left (p=0.010) and right (p=0.001) electrode sites at central locations, and larger amplitudes at midline than at left (p=0.004) and right (p<0.001) electrode sites and at left than at right electrode sites (p=0.020) at central locations. P680 The repeated measures ANOVA (Stimulus Category, Position, and Region) did not reveal, for P680 latency, any significant effect of the factors. The repeated measures ANOVA (Stimulus Category, Position, and Region) showed, for P680 amplitude, a significant effect of the factor Stimulus Category F(2, 26)=5.29, MSE=6.11, p=0.012, as Intentional stimuli presented larger amplitudes than Standard stimuli (p=0.033). In addition, the ANOVA detected a significant effect of the interaction Region x Position F(4, 52)=6.4, ε=0.546, MSE=15.39, p=0.004, as midline electrode sites showed larger amplitudes than left (p=0.028) and right (p=0.016) electrode sites at central locations, whereas left (p=0.047) and midline (p=0.003) electrode sites showed larger amplitudes than right electrode sites at posterior locations. Discussion In the present study the participants had to perform a task while different kind of distracting stimuli (including prospective memory items) were presented in order to check if the intention automatically captured the attention of the participants. Although the paradigm was not successful for obtaining these behavioural differences, evidence has been obtained of different processing for the intentional distractors compared to the other types of distractors in the ERP waveforms, although these distractors were irrelevant for the task. These results seem to support that prospective memory items produce automatic changes in the focus of attention and provide an evidence for the occurrence of spontaneous retrieval of intention processes. The behavioral results showed a significant effect for linguistically significant distractors in latency time for the task of digit classification task when compared with meaningless distractors. These results confirmed that the appearance of new meaningful visual events leads to greater distraction than meaningless visual stimuli, consistent with data obtained by other authors with auditory

9 E. Pérez et al. Distraction processes caused by delayed intentions 19 (Escera et al., 1998) and visual stimuli (Berti & Schröger, 2001, 2004, 2006). These results could be explained by the early intervention of modular lexical word processing processes that occurs both in presence of Neutral and Intentional events. Behaviorally, we found no evidence that the events related to delayed intentions produce greater distraction than those events with meaning not related to delayed intentions. These results do not support the prediction derived from the spontaneous retrieval view that presentation of a PM target should trigger retrieval processes in the period of retention of the intention (Einstein et al., 2005, experiment 5). Nevertheless the use of finer analysis, as is the case in ERP records, showed the existence of neurophysiological modulations that allow establishing that intentional cues are processed in a different way than the other two types of stimuli (Neutral and Standard). In the present study we did not obtain data that intentional cues modulate the N300 amplitude (a wave previously related to prospective memory tasks), and hence, capture attention more than other types of distractors. The N300 in this study has a latency of about 300 ms after the distractor stimuli and 100 ms with respect to the target stimuli; it also has a frontal distribution and shows no modulation in its amplitude by the intentional stimuli and therefore does not appear to correspond to the wave described by West et al. (2001, 2002), but rather to those obtained by Chen et al. (2007). The appearance of intentional stimuli modulations on the N300 component probably requires (as in the work of West et al., 2001, 2002 and Chen et al., 2007) the intentional stimulus to be relevant to the task. The monitoring process associated with execution intervals do not appear to be produced in the intention retention interval. Therefore, further studies are needed to verify the functional significance of N300 and the modulation intentional stimuli exert on the component. The P3 component was analysed using the average amplitude between 400 and 600 ms with respect to the distractor stimulus, which corresponds to the interval between 200 and 400 ms after the target stimulus. Because the target stimuli are the same for all three types of distractor, the observed differences in the mean P3 amplitude should be related to the differential modulator effect of distracting stimuli. In this case, the only distracting stimuli that cause differences in P3 amplitude are intentional ones, which shows amplitudes significantly higher than for the standard stimuli and the neutral stimuli. This result, coupled the fact that there were no differences in P3 amplitudes to neutral words and to the standard stimuli, rules out P3 modulation due to lexical processing of the words. In this regard, the P3 modulation found in this study coincides in the time frame and features of prospective positivity described in other studies, which has been associated with the recovery of an intention from memory (West & Ross-Munroe, 2002). Given the similarity between the P3 component of this study with prospective positivity (West, 2008) in parietal areas and with the P3 component related to the old-new effect of an item studied/not studied (Paller and Kutas, 1992; Rugg, 1995) this old-new effect could contribute to spontaneous retrieval of intentions. Some studies (e.g. West & Krompinger, 2005; West & Wymbs, 2004) have analysed this and found that the modulations found in the central and lateral parietal areas (such as those obtained in this study) are highly consistent with successful prospective remembering and with modulations of the recognition of episodic memory (Rugg, 1995). Anyway, it is necessary to continue the research to verify if these differences in favour of the intentional distractors remain with a suitable control condition in which the neutral distractors are studied before in the same way as the intentional ones. The P680 component showed a frontal-central distribution with larger amplitudes at the midline electrodes. It also showed a modulating effect of distracting stimuli on its amplitude; specifically, its amplitude with intentional stimuli was significantly larger than with standard stimuli, no significant differences between the amplitudes with intentional and neutral stimuli or between amplitudes with neutral and standard stimuli. In the absence of further studies and in the absence of previous data with which to compare the P680 component, and given the late latency of this component, a working hypothesis would be that the amplitude modulation observed in this wave for intentional stimuli could be related to the review or "refresh" of the prospective memories evoked by the presentation of intentional words once the participants have completed the processing related to the relevant task, as well as with modulations related to recognition of episodic memory. In conclusion, intentional words did not produce the intended behavioural distractor effect different than that produced by neutral words. However, the ERP data for P3 and P680

10 20 Revista de Motivación y Emoción 2012, 1, pp components show that intentional distracting stimuli, while they are not relevant for the performance of the task, are processed differently. They capture specific attentional resources involuntarily, in line with the view of spontaneous retrieval (Einstein & McDaniel, 1996). The results of the present study partially support that the occurrence of events related to a delayed intention produce retrieval of the intention, although these retrievals occurred during the retention interval of the intention, a moment when monitoring processes should not be searching for prospective memory events because it is not the appropriate time to perform the delayed intention. An explanation for these results would be that the process of the recognition of intentional events belongs to the exogenous attentional system (McDaniel and Einstein, 2000). Thus, events related to a delayed intention capture the attention involuntarily (response orientation) and stimulate the retrieval of the intention spontaneously while barely consuming resources. An alternative explanation, and not exclusive, could be the intention superiority effect (Goschke and Kuhl, 1993), described as the persisting activation that the representation of an intention has in memory in the retention period, allowing the intentions to be more accessible to consciousness than other nonintentional content. References Arana, J. M., Meilán, J. J. G., & Pérez, E. (2008). The effect of personality variables in the prediction of the execution of different prospective memory tasks in the laboratory. Scandinavian Journal of Psychology, 49, Berti, S., & Schroger, E. (2001). A comparison of auditory and visual distraction effects: Behavioral and eventrelated indices. Cognitive Brain Research, 10(3), Berti, S., & Schröger, E. (2004). Distraction effects in vision: behavioral and event-related potential indices. Neuroreport, 15, Berti, S., & Schröger, E. (2006). Visual distraction: a behavioral and event-related brain potential study in humans. Neuroreport, 17, Chen, Y., Huang, X., Yang, H., Ren, G., Chen, Y., & Yue, C. (2007). Task interference from event-based prospective memory: an event-related potentials study. Neuroreport, 18(3), Craik, F. I. M. (1986). A functional account of age differences in memory. In F. Klix & H. Hagendorf (Eds.), Human memory and cognitive capabilities: Mechanisms and performances (pp ). Amsterdam: Elsevier-North- Holland. De Jong, R. (1997). An intention-activation account of residual switch costs. In S. Monsell & J. Driver (Eds.), Attention and Performance XVIII: Control of Cognitive Processes (pp ). Cambridge: MIT Press. Einstein, G. O., & McDaniel, M. A. (1996). Retrieval processes in prospective memory: Theoretical approaches and some new empirical findings. In M. Brandimonte, G. O. Einstein & M. A. McDaniel (Eds.), Prospective memory: Theory and applications (pp ). Mahwah, NJ: Erlbaum. Einstein, G. O., & McDaniel, M. A. (2005). Evidence for spontaneous retrieval processes in prospective memory. Paper presented at the II International Conference on Prospective Memory. Escera, C., Alho, K., Winkler, I., & Näätänen, R. (1998). Neural mechanisms of involuntary attention to acoustic novelty and change. Journal of Cognitive Neuroscience, 10, Escera, C., Yago, E., Corral, M. J., Corbera, S., & Nuñez, M. I. (2003). Attention capture by auditory significant stimuli: semantic analysis follows attention switching. European Journal of Neuroscience, 18, Goschke, T., & Kuhl, J. (1993). Representation of intention: Persisting activation in memory. Journal of Experimental Psychology: Learning, Memory, and Cognition, 19, Goschke, T., & Kuhl, J. (1996). Remembering what to do: Explicit and implicit memory for intentions. In M. Brandimonte, G. O. Einstein & M. A. McDaniel (Eds.), Prospective Memory: Theory and applications (pp ). Mahwah, NJ: Erlbaum. Gratton, G., Coles, M. G., & Donchin, E. (1983). A new method for off-line removal of ocular artifact. Electroencephalography and Clinical Neurophysiology, 55(4), Guynn, M. J., McDaniel, M. A., & Einstein, G. O. (2001). Remembering to perform actions: A different type of memory? In H. D. Zimmer, R. L. Cohen, M. J. Guynn, J. Engelkamp, R. Kormi-Nouri & M. A. Foley (Eds.), Memory for action: A distinct form of episodic memory? (pp ). New York: Oxford University Press. Kok, A. (2001). On the utility of P3 amplitude as a measure of processing capacity. Psychophysiology, 38, Mäntylä, T. (1996). Activating actions and interrupting intentions: Mechanisms of retrieval sensitization in prospective memory. In M. Brandimonte, G. Einstein & M. McDaniel (Eds.), Prospective memory: Theory and applications (pp ). Mahwah, NJ: Erlbaum. Marsh, R. L., & Hicks, J. L. (1998). Event-based prospective memory and executive control of working

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