Differential effects of uncertainty on LPP responses to emotional events during explicit and implicit anticipation

https://doi.org/10.1016/j.ijpsycho.2018.04.012Get rights and content

Highlights

  • Studies have shown the effects of uncertainty on ERP responses to emotional events.

  • Whether the effects differ following explicit and implicit anticipation is unknown.

  • The LPP was enhanced for uncertain negative pictures in the explicit condition.

  • However, uncertainty reduced the LPP to negative pictures in the implicit condition.

Abstract

Previous studies have investigated whether uncertainty influences neural responses to emotional events. The findings of such studies, particularly with respect to event-related potentials (ERPs), have been controversial due to several factors, such as the stimuli that serve as cues and the emotional content of the events. However, it is still unknown whether the effects of uncertainty on ERP responses to emotional events are influenced by anticipation patterns (e.g., explicit or implicit anticipation). To address this issue, participants in the present study were presented with anticipatory cues and then emotional (negative and neutral) pictures. The cues either did or did not signify the emotional content of the upcoming picture. In the inter-stimulus intervals between cues and pictures, participants were asked to estimate the expected probability of the occurrence of a specific emotional category of the subsequent picture based on a scale in the explicit anticipation condition, while in the implicit condition, participants were asked to indicate, using a number on a scale, which color was different from the others. The results revealed that in the explicit condition, uncertainty increased late positive potential (LPP) responses, particularly for negative pictures, whereas LPP responses were larger for certain negative pictures than for uncertain negative pictures in the implicit condition. The findings in the present study suggest that the anticipation pattern influences the effects of uncertainty when evaluation of negative events.

Introduction

The ability to anticipate an upcoming event on the basis of experience, knowledge and information about the present state and environment is of critical importance in an organism's survival, as it may protect individuals from harm and danger. Due to the ever-changing world, however, individuals are often uncertain about the consequences, particularly the emotional consequences, of upcoming events. This uncertainty has been suggested to be a disadvantage when preparing for upcoming dangers (e.g., Lin et al., 2014a), leading to overestimating an upcoming threat (Dieterich et al., 2016; Grupe and Nitschke, 2011; Sarinopoulos et al., 2010) and producing fear and anxiety (Grupe and Nitschke, 2013).

In laboratory studies, a cue-event paradigm is often used to investigate the effects of uncertainty (e.g., Dieterich et al., 2016, Dieterich et al., 2017; Gole et al., 2012; Grupe and Nitschke, 2011; Lin et al., 2015a, Lin et al., 2017; Onoda et al., 2006, Onoda et al., 2007, Onoda et al., 2008; Sarinopoulos et al., 2010; Yang et al., 2012). In this paradigm, participants are presented with emotional events. The events are preceded by anticipatory cues that either do or do not signify the specific emotional category of the following event. Using this paradigm, previous studies have investigated whether uncertainty modulates neural responses to upcoming emotional events; however, the findings, particularly with respect to event-related potentials (ERPs), have been controversial (e.g., Dieterich et al., 2016, Dieterich et al., 2017; Gole et al., 2012; Lin et al., 2015a, Lin et al., 2017; Yang et al., 2012), possibly due to the stimuli serving as cues (e.g., Yang et al., 2012) and the emotional category of the events (e.g., Gole et al., 2012; Lin et al., 2015a, Lin et al., 2017).

Another possible reason for the discrepant findings may be related to how individuals anticipate the emotional consequence (i.e., the anticipation pattern). Previous studies have proposed two patterns of anticipation, i.e., implicit and explicit anticipation patterns. In implicit anticipation, participants simply view anticipatory cues during the anticipation phaseand are not explicitly asked to anticipate the emotional consequence (e.g., Gole et al., 2012; Lin et al., 2015a, Lin et al., 2017; Onoda et al., 2006, Onoda et al., 2007, Onoda et al., 2008; Yang et al., 2012); whereas in explicit anticipation, participants anticipate the consequence explicitly (e.g., by estimating the probability of the occurrence of a specific emotional category of the upcoming event; e.g., Dieterich et al., 2016, Dieterich et al., 2017; Grupe and Nitschke, 2011). Using implicit anticipation patterns, Gole et al. (2012) showed that uncertainty increased the N2 responses but reduced the late positive potential (LPP) responses to both negative and neutral pictures. Similar to Gole et al.'s (2012) study, our previous studies (Lin et al., 2015a, Lin et al., 2017) also found a larger N2 but smaller LPP for uncertain compared to certain negative pictures. In addition, when negative pictures were presented with positive pictures, we found a smaller P2 for uncertain compared to certain negative pictures (Lin et al., 2015a). When the anticipation is explicit, however, Dieterich et al. (2016) showed that emotionally uncertain compared to certain pictures evoked a larger P2 and LPP regardless of the emotional content (e.g., negative and neutral) of the pictures. In Dieterich et al.'s (2017) other study, the authors also observed increased LPP resposnes to emotionally uncertain pictures.

Regarding the ERP components, the P2, which peaks at approximately 150 ms over frontocentral scalp sites, is thought to be associated with feature detection (Thorpe et al., 1996; Olofsson et al., 2008; Yuan et al., 2007). In subsequent time ranges, the N2, which develops approximately 200 ms after stimulus onset over anterior scalp sites, is thought to be related to stimulus discrimination and classification (e.g., Folstein and Van Petten, 2008; Olofsson et al., 2008; Ritter et al., 1979; Yuan et al., 2007). In a later time range, the LPP is a positive component that is widely distributed over frontoparietal scalp sites and starts approximately 500 ms after the onset of a stimulus. This component has been suggested to be related to emotional evaluations (e.g., Hajcak and Nieuwenhuis, 2006; Moser et al., 2006; Olofsson et al., 2008; Schupp et al., 2004a, Schupp et al., 2004b). Therefore, the abovementioned studies suggest that when the anticipation is implicit, uncertainty may reduce feature detection during the presentation of emotional events, in particular negative events, but at subsequent time ranges, enhance the processing in terms of discrimination and classification and later reduce emotional evaluations towards the events. For explicit anticipation, however, uncertainty increases emotional evaluations of the events. In some cases, uncertainty may be facilicated by detecting the features of the events.

While the findings in previous studies may indicate that the effects of uncertainty on ERP responses to emotional events are distinct for different anticipation patterns, considering that these findings were seen in different studies, it cannot be excluded that these differential uncertainty effects are related to other factors, such as samples and stimuli. Therefore, the present study aimed to manipulate the pattern of anticipation directly to investigate whether anticipation pattern influences the effects of uncertainty on ERP respnoses to emotional events. To address this issue, participants in the present study were asked to view anticipatory cues and then emotional (negative and neutral) pictures. The cues either signified the emotional content of the upcoming pictures (i.e., the certain condition) or did not (i.e., the uncertain condition). In the explicit anticipation condition, participants were asked to anticipate the emotional consequence of the subsequent pictures in the intervals between cues and pictures and to indicate the expected probability of the occurrence of a specific emotional category in the subsequent picture according to a scale. In the implicit condition, participants were asked to press one of the numbers on a scale that depicted into different colors. The presentation of the scale and performance of the number pressing task were to used to reduce differences due to visual stimuli and task difficulty, respectively, between the explicit and implicit conditions. Additionally, electroencephalograms (EEGs) were recorded during the actual experiment.

Based on the abovementioned studies (e.g., Dieterich et al., 2016, Dieterich et al., 2017; Gole et al., 2012; Lin et al., 2015a, Lin et al., 2017), we predicted that in the explicit anticipation condition, uncertain compared to certain emotional pictures, particularly negative pictures, would evoke larger LPP amplitudes For the P2, although Dieterich et al. (2016) observed increased amplitude for emotionally uncertain pictures in the explicit condition, using similar approaches, this effect could not be replicated in another of their studies (Dieterich et al., 2017). Therefore, it was still unknown whether this effect would be evident in the present study. In the implicit condition, it was predicted that uncertainty would elicit larger N2 amplitudes but smaller LPP amplitudes for emotional pictures. Note that while P2 was found to be reduced by uncertain negative pictures in the implicit condition, when positive and negative pictures were used (Lin et al., 2015a); when negative and neutral pictures were used, there was no effect of uncertainty on the P2 (Gole et al., 2012; Lin et al., 2017). Given that the present study used negative and neutral pictures, we predicted that uncertainty would not affect the P2 response to negative pictures.

Section snippets

Participants

Twenty-eight healthy undergraduate and postgraduate students (16 females; 18–26 years old, M = 19.98, SD = 1.91)1

Probability estimation of uncertain negative pictures in the explicit condition

Consistent with previous studies (Dieterich et al., 2016; Grupe and Nitschke, 2011; Sarinopoulos et al., 2010), a one-sample t-test showed that the estimated probability regarding uncertain negative pictures was significantly higher than 0.50 (M ± SD = 0.55 ± 0.10; t(27) = 2.92, p = 0.007, d = 0.55).

Response accuracy and times for the number pressing task in the implicit condition

Regarding response accuracy, the analysis did not show an effect of uncertainty (F(2, 54) = 2.33, p = 0.107, ηp2 = 0.08; certain-negative: 0.91 ± 0.19, certain-neutral: 0.91 ± 0.20, uncertain:

Discussion

The present study investigated whether the anticipation pattern (e.g., explicit and implicit anticipation) influences the effects of uncertainty on ERP responses to emotional pictures. The results showed that uncertainty enhanced the LPP responses to emotional pictures, particularly negative pictures, in the explicit condition, whereas in the implicit condition, the LPP was larger for certain negative pictures than for uncertain negative pictures. The findings suggest that the effects of

Conclusions

The present study investigated the effects of anticipation pattern on the effects of uncertainty on ERP responses to emotional pictures. The results showed that in the explicit condition, LPPs were larger for emotionally uncertain pictures than for certain pictures, particularly negative pictures, whereas this effect of uncertainty was reversed in the implicit condition. The findings indicate that anticipation patterns modulate the effects of uncertainty on the evaluation of negative events.

Acknowledgements

This work is supported by key platforms and major research projects of innovative young talents program in Guangdong Universities (Natural science, 2016KQNCX110, Name of project: emotional events are affected by the emotional content of anticipatory cues: evidence from electrophysiology), by the Project of Innovative and Strong University (The Enhancement of the Ability of Independence and Innovation and the Ability of Social Service; the name of the study: Explicit and implicit anticipations

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