Preparatory process explanation

The preparatory process explanation of the Ps-Dm effect assumes that the mental readiness required to deal with the upcoming stimuli leads to memory formation (Galli, Wolpe, et al., 2011). It is argued that if the purpose of preparation is to facilitate encoding of an emotionally negative event, then one would expect a benefit for emotional memory at the post-anticipation period that was absent in the previous study (Galli, Griffiths, et al., 2012; Galli, Wolpe, et al., 2011). The absence of Dm effect in response to pictures makes the reliability of Ps-Dm effect questionable (Galli et al., 2011; Gruber & Leun; Otten, 2010; Otten et al., 2006; Otten, Quayle, & Puvaneswaran, 2010; Park & Rugg, 2010). It is proposed that for a strong Ps-Dm effect, the pre-stimulus, post-stimulus, and behavioural results may show a linear relation. Without this direct relationship, the Ps-Dm effect might be merely a reflection of random fluctuations in attention and not an index of encoding or preparation at work.

The anticipatory model in this study proposes that pre- and post-anticipation processes are not isolated. Anticipation, preparation, and action are closely linked to each other (Castelfranchi & Miceli, 2011). Anticipation operates by preparing the system to become active soon, either to have more efficient processing, (Castelfranchi & Miceli, 2011; Lobanov, Zeidan, McHaffie, Kraft, & Coghill, 2014; van Boxtel & Böcker, 2004). It was found in studies that involved real electrical shocks and pain that participants’ reactions were modulated according to the level of expectation of pain (Koyama, McHaffie, Laurienti, & Coghill, 2005). Brain activity in response to high pain cues differed from activity associated with cues signalling small pain. This signifies that the anticipation is related to the impending emotional event, which in turn plays a role in modulating neural responses at the pre-stimulus phase. In this context, anticipatory activity tends to be linked to post- stimulus activity. Taking together, these studies provide evidence that pre- and post- stimulus mechanisms are not dissociable or inextricable. Although, if they are in fact

107 dissociable, then the findings might be explained regarding ‘Random Fluctuation Hypothesis’.

Ps-Dm effects have been studied beyond the ERP literature on cortical measures of anticipation. For instance, the type of cues (pictorial and verbal) and cue duration are two crucial factors in the ERP theoretical framework of anticipation. Before discussing certain drawbacks associated with methodology, a brief review of important cortical measures of anticipation is given. In the electrophysiological literature, anticipation is typically studied using a cueing paradigm that involves two types of stimuli: a cue stimulus (S1) and a picture stimulus (S2). Electrical brain potentials for S1 and S2 are distinguished as the Contingent Negative Variation: CNV (Walter, Cooper, Aldridge, McCallum, & Winter, 1964) ) and the Stimulus Preceding Negativity: SPN, respectively. Both ERP components are slow waves with negative-going deflection. However, the CNV is an early wave associated with the properties of the cue (S1). It is larger at frontocentral sites and usually requires a motor response to S2. In contrast, the SPN is a late wave, which is associated with the properties of emotional stimuli (Boxtel et al., 2004; Buodo et al., 2012). Functional significance of the SPN is interpreted as the preparatory activity aimed at speeding up brain processes for emotional stimuli (Luck and Kappenman, 2012).

A brief review of the theoretical framework of the cortical measures of anticipation raised two issues crucial to the explanation of Ps-Dm effect. First, cues were pictorial in nature, that is, cartoon-like faces were used. Second, they remained on the screen for the duration of anticipation (Galli et al., 2014; Galli, Wolpe, et al., 2011). ERP measurement, especially the CNV, is related to the properties of the cues (van Boxtel & Böcker, 2004). By nature, anticipation is a perceptual process (V. Boxtel et al., 2004). It is speculated that the use of pictorial cues might have become confused with the perceptual anticipation. It is plausible that face-like cues were the driver of the Ps- Dm effect rather than legitimate anticipation- related activity. In all the experiments of this project, instead of cartoon faces, the upper case letters O (neutral) and X (negative) have been used. These cues have no intrinsic value; rather they were manipulated as anticipatory attention to stimuli. During the instructions and practice phase, cues were conditioned to the type of upcoming picture. This was done to help participants form a mental representation of the image by applying the perceptual meaning of the cue. That is, representation was tied to the perception of the cues.

The other crucial aspect of the Ps-Dm effect study is that the pictorial cues remained on the screen for the whole duration of the anticipatory period (1400ms) and disappeared only 100ms before the picture onset (Galli, et al., 2011). If the preparatory process hypothesis is

108 reliable, and preparation facilitates encoding at the pre-stimulus phase (for Ps-Dm), then the Ps-Dm effect might have been present at 100ms before the picture onset. The Ps-Dm effect reported in Gallli, et al., (2011) is just specific to the instant response to the cues. Evidence regarding SPN might be focused as an index of preparation for emotional anticipation during the anticipatory phase. About emotional anticipation, SPN can be considered as the ERP counterpart of the emotion effect in emotion memory literature. At the anticipatory phase, it can be measured as the amplitude difference between the brain waves of anticipated emotional and neutral trials. An SPN analysis could yield evidence to support a preparatory process that modulates the Ps-Dm effect. However, no SPN analysis has conducted in the relevant study (Galli et al., 2011).

The findings of the study in Chapter 4 demonstrated that Informative and Non-Informative anticipatory cues modulated emotional memory for recollected pictures at the behavioural level. Memory performance under the No-Cue condition did not yield similar results. Findings of this study led to focus on the neural processing of the anticipatory behaviour, as the data came from a behavioural study and was beyond the scope of that research. In the current experiment, the event-related potential (ERP) technique has been used to investigate the questions focused on in study 1. To reiterate, does the Ps-Dm effect reflect intentional preparatory processes where the presence of cue is required (cues needed) or is it only result of random fluctuation if similar Ps-Dm activity is seen in the absence of cues. Ps-Dm effect was investigated by making a distinction between two anticipatory phases: One for the time the cue remains on the screen (0-1000ms) and other when it disappears from the screen from 1000ms to 3000ms till the onset of the picture. In the Info-Cue condition, Ps-Dm effect is expected to be found during the cue display period; it would enable the replication of a preparatory-process-based explanation found in the study by Galli et al. (2011). The Stimulus-Preceding Negativity (SPN), an indicator of affective anticipation, would be examined in the later time windows.

If the Ps-Dm effect was also found in the No-Cue condition, it would indicate that cues or preparatory processing are not necessary to elicit an effect, and findings would be discussed with respect to the random fluctuation hypothesis. Assuming that physiological arousal becomes heightened in the unpredictable condition (Herry et al., 2007), it is predicted that participants would rate negative pictures more negatively in the No-Cue condition.

109 5.3 Method